diff --git a/desktop-app/resources/index.html b/desktop-app/resources/index.html
index 7964c7c..8740ec6 100644
--- a/desktop-app/resources/index.html
+++ b/desktop-app/resources/index.html
@@ -406,44 +406,122 @@ <h5>Menu</h5>
           </div>
         </div>
 
-        <!-- Find & Replace Modal -->
-        <div id="find-replace-modal" class="reset-modal-overlay modal-overlay" role="dialog" aria-modal="true" aria-labelledby="find-replace-title" aria-hidden="true" style="display:none;">
-          <div class="reset-modal-box reset-modal-box--wide reset-modal-box--xl modal-box">
-            <div class="modal-header">
-              <p id="find-replace-title" class="reset-modal-message">Find &amp; Replace</p>
-              <button type="button" class="modal-close-btn" id="find-replace-close-icon" aria-label="Close find and replace dialog">
-                <i class="bi bi-x-lg"></i>
+        <!-- Find & Replace Floating Panel -->
+        <div id="find-replace-modal" class="find-replace-panel" role="region" aria-label="Find and Replace" style="display:none;">
+          <div class="find-replace-header" id="find-replace-drag-handle">
+            <span class="find-replace-title"><i class="bi bi-search me-1"></i> Find &amp; Replace</span>
+            <div class="find-replace-header-actions">
+              <button type="button" class="panel-icon-btn" id="find-replace-dock" title="Toggle Dock Mode" aria-label="Toggle Dock Mode"><i class="bi bi-layout-sidebar-reverse"></i></button>
+              <button type="button" class="panel-icon-btn" id="find-replace-close-icon" aria-label="Close find and replace panel"><i class="bi bi-x-lg"></i></button>
+            </div>
+          </div>
+          <div class="find-replace-body">
+            <!-- Find Row -->
+            <div class="find-replace-field-row">
+              <div class="find-input-container">
+                <input type="text" id="find-replace-input" class="find-input-field" placeholder="Find" aria-label="Find query" />
+                <div class="find-options-group">
+                  <button type="button" class="find-option-btn" id="find-case" title="Match Case (Aa)" aria-label="Match Case">Aa</button>
+                  <button type="button" class="find-option-btn" id="find-word" title="Match Whole Word (W)" aria-label="Match Whole Word">W</button>
+                  <button type="button" class="find-option-btn" id="find-regex" title="Use Regular Expression (.*)" aria-label="Use Regular Expression">.*</button>
+                  <button type="button" class="find-option-btn" id="find-sel" title="Find in Selection (Sel)" aria-label="Find in Selection"><i class="bi bi-align-start"></i></button>
+                </div>
+              </div>
+            </div>
+            
+            <!-- Real-time Regex Error Box -->
+            <div id="find-replace-error" class="find-error-drawer" style="display:none;">
+              <i class="bi bi-exclamation-triangle-fill me-1"></i> <span id="regex-error-msg"></span>
+            </div>
+
+            <!-- Replace Row -->
+            <div class="find-replace-field-row">
+              <div class="replace-input-container">
+                <input type="text" id="find-replace-with" class="find-input-field" placeholder="Replace" aria-label="Replace with" />
+                <div class="find-options-group">
+                  <button type="button" class="find-option-btn" id="replace-preserve-case" title="Preserve Case (Ab)" aria-label="Preserve Case">Ab</button>
+                  <button type="button" class="find-option-btn active" id="find-wrap" title="Wrap Around (Wrap)" aria-label="Wrap Around" aria-pressed="true">Wrap</button>
+                </div>
+              </div>
+            </div>
+
+            <!-- Meta Controls Row -->
+            <div class="find-replace-meta-row">
+              <span id="find-replace-count" class="find-match-count" role="status" aria-live="polite">0 of 0 matches</span>
+              <div class="find-nav-group">
+                <button type="button" class="find-nav-arrow-btn" id="find-prev" title="Previous match (Shift+Enter)" aria-label="Previous match" disabled>
+                  <i class="bi bi-chevron-up"></i>
+                </button>
+                <button type="button" class="find-nav-arrow-btn" id="find-next" title="Next match (Enter)" aria-label="Next match" disabled>
+                  <i class="bi bi-chevron-down"></i>
+                </button>
+              </div>
+            </div>
+
+            <!-- Advanced Drawer Toggle -->
+            <div class="find-drawer-toggle-row">
+              <button type="button" class="drawer-toggle-btn" id="fr-drawer-toggle" aria-expanded="false">
+                <i class="bi bi-chevron-right me-1"></i> Advanced Options
               </button>
             </div>
-            <div class="modal-body">
-              <div class="reset-modal-field">
-                <label class="reset-modal-label" for="find-replace-input">Find</label>
-                <input type="text" id="find-replace-input" class="rename-modal-input" placeholder="Find word or phrase" />
+
+            <!-- Collapsible Drawer -->
+            <div id="fr-drawer-content" class="find-replace-drawer-content" style="display:none;">
+              <div class="drawer-field">
+                <label for="find-replace-scope" class="drawer-label">Scope Filter</label>
+                <select id="find-replace-scope" class="drawer-select">
+                  <option value="entire">Entire Document</option>
+                  <option value="heading">Headings only</option>
+                  <option value="code">Code blocks only</option>
+                  <option value="latex">LaTeX blocks only</option>
+                  <option value="mermaid">Mermaid blocks only</option>
+                  <option value="plain">Plain text only</option>
+                </select>
               </div>
-              <div class="reset-modal-field">
-                <label class="reset-modal-label" for="find-replace-with">Replace</label>
-                <input type="text" id="find-replace-with" class="rename-modal-input" placeholder="Replace with" />
+              <div class="drawer-field">
+                <label for="find-replace-history" class="drawer-label">Search History</label>
+                <select id="find-replace-history" class="drawer-select">
+                  <option value="">Recent queries...</option>
+                </select>
               </div>
-              <div class="find-replace-meta">
-                <span id="find-replace-count" class="find-match-count">0 of 0 matches</span>
-                <div class="find-replace-nav">
-                  <button type="button" class="tool-button find-nav-btn" id="find-prev" title="Previous match" aria-label="Previous match">
-                    <i class="bi bi-chevron-up"></i>
-                  </button>
-                  <button type="button" class="tool-button find-nav-btn" id="find-next" title="Next match" aria-label="Next match">
-                    <i class="bi bi-chevron-down"></i>
-                  </button>
-                </div>
+              <div class="drawer-field check-field">
+                <input type="checkbox" id="find-replace-diff-toggle" class="drawer-checkbox" />
+                <label for="find-replace-diff-toggle" class="drawer-label-checkbox">Show Diff Preview before replace</label>
+              </div>
+            </div>
+          </div>
+
+          <!-- Actions Footer -->
+          <div class="find-replace-actions-footer">
+            <button type="button" class="fr-action-btn" id="find-replace-current" disabled>Replace</button>
+            <button type="button" class="fr-action-btn" id="find-replace-all" disabled>Replace All</button>
+            <button type="button" class="fr-action-btn secondary" id="find-replace-close">Close</button>
+          </div>
+        </div>
+
+        <!-- Diff Preview Modal -->
+        <div id="find-replace-diff-modal" class="reset-modal-overlay modal-overlay" role="dialog" aria-modal="true" aria-labelledby="diff-modal-title" aria-hidden="true" style="display:none;">
+          <div class="reset-modal-box reset-modal-box--xl modal-box">
+            <div class="modal-header">
+              <p id="diff-modal-title" class="reset-modal-message">Replace All Diff Preview</p>
+              <button type="button" class="modal-close-btn" id="find-replace-diff-close-icon" aria-label="Close diff preview dialog">
+                <i class="bi bi-x-lg"></i>
+              </button>
+            </div>
+            <div class="modal-body diff-preview-body">
+              <p class="modal-subtext">Review the proposed changes before committing them to the document.</p>
+              <div class="diff-container" id="find-replace-diff-container">
+                <!-- Populated dynamically -->
               </div>
             </div>
             <div class="reset-modal-actions">
-              <button class="reset-modal-btn reset-modal-cancel" id="find-replace-close">Close</button>
-              <button class="reset-modal-btn" id="find-replace-current">Replace</button>
-              <button class="reset-modal-btn" id="find-replace-all">Replace All</button>
+              <button class="reset-modal-btn reset-modal-cancel" id="find-replace-diff-cancel">Cancel</button>
+              <button class="reset-modal-btn reset-modal-confirm" id="find-replace-diff-confirm">Commit Replacements</button>
             </div>
           </div>
         </div>
 
+
         <!-- Help Modal -->
         <div id="help-modal" class="reset-modal-overlay modal-overlay" role="dialog" aria-modal="true" aria-labelledby="help-modal-title" aria-hidden="true" style="display:none;">
           <div class="reset-modal-box reset-modal-box--xl modal-box">
diff --git a/desktop-app/resources/js/script.js b/desktop-app/resources/js/script.js
index e776146..5562b70 100644
--- a/desktop-app/resources/js/script.js
+++ b/desktop-app/resources/js/script.js
@@ -3710,35 +3710,306 @@ This is a fully client-side application. Your content never leaves your browser
     lineNumbers.scrollTop = markdownEditor.scrollTop;
   }
 
-  function computeFindMatches(value, query) {
-    if (!query) return [];
-    const haystack = value.toLowerCase();
-    const needle = query.toLowerCase();
-    const matches = [];
-    let index = haystack.indexOf(needle);
-    while (index !== -1) {
-      matches.push({ start: index, end: index + needle.length });
-      index = haystack.indexOf(needle, index + needle.length);
+  // Class encapsulating Search & Replace Engine
+  class FindReplaceEngine {
+    constructor(editor) {
+      this.editor = editor;
+      this.history = { find: [], replace: [] };
+      this.activeMatches = [];
+      this.currentMatchIndex = -1;
+    }
+
+    buildASTScopeMap(text) {
+      if (typeof marked === 'undefined' || !marked.lexer) return [];
+      try {
+        const tokens = marked.lexer(text);
+        const scopeMap = [];
+        let currentIndex = 0;
+
+        const traverse = (tokenList) => {
+          for (const token of tokenList) {
+            const start = text.indexOf(token.raw, currentIndex);
+            if (start === -1) continue;
+            const end = start + token.raw.length;
+            currentIndex = end;
+
+            let scope = 'plain';
+            if (token.type === 'heading') scope = 'heading';
+            else if (token.type === 'code') {
+              if (token.lang === 'mermaid') scope = 'mermaid';
+              else scope = 'code';
+            } else if (token.type === 'paragraph' && token.raw.startsWith('$$') && token.raw.endsWith('$$')) {
+              scope = 'latex';
+            }
+
+            scopeMap.push({ start, end, scope, type: token.type });
+            if (token.tokens) traverse(token.tokens);
+          }
+        };
+
+        traverse(tokens);
+        return scopeMap;
+      } catch (e) {
+        console.warn("AST scope parsing failed:", e);
+        return [];
+      }
+    }
+
+    compileRegExp(query, isRegex, isCaseSensitive, isWholeWord) {
+      if (!query) return null;
+      let pattern = isRegex ? query : query.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+      if (isWholeWord) {
+        pattern = `\\b${pattern}\\b`;
+      }
+      const flags = isCaseSensitive ? 'gd' : 'gid';
+      return new RegExp(pattern, flags);
+    }
+
+    executeSearch(options) {
+      const { query, isRegex, isCaseSensitive, isWholeWord, scopeFilter, findInSelection } = options;
+      const fullText = this.editor.value || '';
+      
+      let searchRange = { start: 0, end: fullText.length };
+      if (findInSelection) {
+        searchRange.start = this.editor.selectionStart;
+        searchRange.end = this.editor.selectionEnd;
+      }
+
+      let regex;
+      try {
+        regex = this.compileRegExp(query, isRegex, isCaseSensitive, isWholeWord);
+      } catch (err) {
+        throw new Error(err.message);
+      }
+
+      if (!regex) {
+        this.activeMatches = [];
+        this.currentMatchIndex = -1;
+        return this.activeMatches;
+      }
+
+      const rawMatches = [];
+      let match;
+      
+      while ((match = regex.exec(fullText)) !== null) {
+        if (match.index >= searchRange.end) break;
+        if (match.index >= searchRange.start) {
+          rawMatches.push({
+            start: match.index,
+            end: match.index + match[0].length,
+            value: match[0],
+            groups: match.groups || null,
+            matchArray: match
+          });
+        }
+        if (regex.lastIndex === match.index) {
+          regex.lastIndex++;
+        }
+      }
+
+      if (scopeFilter && scopeFilter !== 'entire') {
+        const scopeMap = this.buildASTScopeMap(fullText);
+        this.activeMatches = rawMatches.filter(m => {
+          const matchingScope = scopeMap.find(s => m.start >= s.start && m.end <= s.end);
+          return matchingScope && matchingScope.scope === scopeFilter;
+        });
+      } else {
+        this.activeMatches = rawMatches;
+      }
+
+      this.currentMatchIndex = this.activeMatches.length > 0 ? 0 : -1;
+      this.addHistory('find', query);
+      return this.activeMatches;
+    }
+
+    preserveCase(source, replacement) {
+      if (source === source.toUpperCase()) {
+        return replacement.toUpperCase();
+      }
+      if (source === source.toLowerCase()) {
+        return replacement.toLowerCase();
+      }
+      if (source[0] === source[0].toUpperCase() && source.slice(1) === source.slice(1).toLowerCase()) {
+        return replacement[0].toUpperCase() + replacement.slice(1).toLowerCase();
+      }
+      return replacement;
+    }
+
+    applyCaptureGroups(match, replacementTemplate) {
+      if (!match.matchArray) return replacementTemplate;
+      let result = replacementTemplate;
+      
+      result = result.replace(/\$(\d+)/g, (m, number) => {
+        const idx = parseInt(number, 10);
+        return match.matchArray[idx] !== undefined ? match.matchArray[idx] : m;
+      });
+
+      if (match.groups) {
+        result = result.replace(/\$<([^>]+)>/g, (m, name) => {
+          return match.groups[name] !== undefined ? match.groups[name] : m;
+        });
+      }
+
+      return result;
+    }
+
+    executeReplace(match, replacementTemplate, options) {
+      const { preserveCase, isRegex } = options;
+      const text = this.editor.value;
+
+      let finalReplacement = replacementTemplate;
+      if (isRegex) {
+        finalReplacement = this.applyCaptureGroups(match, finalReplacement);
+      }
+      if (preserveCase) {
+        finalReplacement = this.preserveCase(match.value, finalReplacement);
+      }
+
+      const before = text.slice(0, match.start);
+      const after = text.slice(match.end);
+      this.editor.value = before + finalReplacement + after;
+      this.editor.dispatchEvent(new Event('input', { bubbles: true }));
+
+      this.addHistory('replace', replacementTemplate);
+      return finalReplacement.length - match.value.length;
+    }
+
+    addHistory(type, query) {
+      if (!query) return;
+      const list = this.history[type];
+      const index = list.indexOf(query);
+      if (index !== -1) {
+        list.splice(index, 1);
+      }
+      list.unshift(query);
+      if (list.length > 10) {
+        list.pop();
+      }
+    }
+  }
+
+  // Verification helper for rich text blocks
+  function validateBlockSyntax(originalBlockText, newBlockText, scope) {
+    if (scope === 'latex') {
+      const origDisplay = (originalBlockText.match(/\$\$/g) || []).length;
+      const newDisplay = (newBlockText.match(/\$\$/g) || []).length;
+      const origInline = (originalBlockText.match(/[^\$]\$[^\$]/g) || []).length;
+      const newInline = (newBlockText.match(/[^\$]\$[^\$]/g) || []).length;
+
+      if (origDisplay !== newDisplay || origInline !== newInline) {
+        return { valid: false, reason: "LaTeX math block delimiters are unbalanced." };
+      }
+    }
+
+    if (scope === 'mermaid') {
+      const diagramTypePattern = /^(graph|flowchart|sequenceDiagram|classDiagram|stateDiagram-v2|erDiagram|gantt|pie|quadrantChart|c4Context|mindmap|timeline|zenuml)/i;
+      if (!diagramTypePattern.test(newBlockText.trim())) {
+        return { valid: false, reason: "Missing diagram type definition (e.g. flowchart TD)." };
+      }
+    }
+    return { valid: true };
+  }
+
+  // Global Engine Instance
+  let frEngine = null;
+  let isFrDocked = false;
+  let dragOffset = { x: 0, y: 0 };
+  let isPanelDragging = false;
+
+  function initFindReplacePanelDrag() {
+    const handle = document.getElementById('find-replace-drag-handle');
+    const panel = document.getElementById('find-replace-modal');
+    if (!handle || !panel) return;
+
+    handle.addEventListener('mousedown', (e) => {
+      if (isFrDocked) return;
+      if (e.target.closest('.find-replace-header-actions')) return;
+      isPanelDragging = true;
+      dragOffset.x = e.clientX - panel.offsetLeft;
+      dragOffset.y = e.clientY - panel.offsetTop;
+      document.body.classList.add('resizing');
+    });
+
+    document.addEventListener('mousemove', (e) => {
+      if (!isPanelDragging || isFrDocked) return;
+      const x = e.clientX - dragOffset.x;
+      const y = e.clientY - dragOffset.y;
+      
+      // Keep panel inside viewport boundaries
+      const maxX = window.innerWidth - panel.offsetWidth;
+      const maxY = window.innerHeight - panel.offsetHeight;
+      panel.style.left = `${Math.max(0, Math.min(maxX, x))}px`;
+      panel.style.top = `${Math.max(0, Math.min(maxY, y))}px`;
+      panel.style.right = 'auto';
+    });
+
+    document.addEventListener('mouseup', () => {
+      if (isPanelDragging) {
+        isPanelDragging = false;
+        document.body.classList.remove('resizing');
+      }
+    });
+  }
+
+  function toggleFrDockMode() {
+    const panel = document.getElementById('find-replace-modal');
+    const dockBtn = document.getElementById('find-replace-dock');
+    const editorWrapper = document.querySelector('.editor-dock-wrapper') || document.querySelector('.content-container');
+    if (!panel || !dockBtn || !editorWrapper) return;
+
+    isFrDocked = !isFrDocked;
+    if (isFrDocked) {
+      panel.classList.add('docked');
+      panel.style.left = 'auto';
+      panel.style.top = 'auto';
+      panel.style.right = 'auto';
+      // Append panel to dock container
+      editorWrapper.appendChild(panel);
+      dockBtn.innerHTML = '<i class="bi bi-window"></i>';
+      dockBtn.title = "Toggle Floating Mode";
+    } else {
+      panel.classList.remove('docked');
+      // Reset position and float on body
+      document.body.appendChild(panel);
+      panel.style.top = '100px';
+      panel.style.right = '20px';
+      panel.style.left = 'auto';
+      dockBtn.innerHTML = '<i class="bi bi-layout-sidebar-reverse"></i>';
+      dockBtn.title = "Toggle Dock Mode";
     }
-    return matches;
   }
 
   function updateFindControls() {
-    if (!findReplaceCount) return;
     const total = findMatches.length;
     const current = total && activeFindIndex >= 0 ? activeFindIndex + 1 : 0;
-    findReplaceCount.textContent = current + ' of ' + total + ' matches';
+    
+    const countSpan = document.getElementById('find-replace-count');
+    if (countSpan) {
+      countSpan.textContent = `${current} of ${total} matches`;
+    }
+
+    const prevBtn = document.getElementById('find-prev');
+    const nextBtn = document.getElementById('find-next');
+    const replaceCurrentBtn = document.getElementById('find-replace-current');
+    const replaceAllBtn = document.getElementById('find-replace-all');
+
     const hasMatches = total > 0;
     const hasQuery = !!(findReplaceInput && findReplaceInput.value);
-    if (findReplacePrev) findReplacePrev.disabled = !hasMatches;
-    if (findReplaceNext) findReplaceNext.disabled = !hasMatches;
-    if (findReplaceCurrent) findReplaceCurrent.disabled = !hasMatches;
-    if (findReplaceAll) findReplaceAll.disabled = !hasQuery || !hasMatches;
+
+    if (prevBtn) prevBtn.disabled = !hasMatches;
+    if (nextBtn) nextBtn.disabled = !hasMatches;
+    if (replaceCurrentBtn) replaceCurrentBtn.disabled = !hasMatches;
+    if (replaceAllBtn) replaceAllBtn.disabled = !hasQuery || !hasMatches;
   }
 
   function refreshFindMatches(options) {
     const opts = options || {};
     const query = findReplaceInput ? findReplaceInput.value : '';
+    const errorBox = document.getElementById('find-replace-error');
+    const errorMsg = document.getElementById('regex-error-msg');
+
+    if (errorBox) errorBox.style.display = 'none';
+
     if (!isFindModalOpen || !query) {
       findMatches = [];
       activeFindIndex = -1;
@@ -3746,7 +4017,31 @@ This is a fully client-side application. Your content never leaves your browser
       updateFindHighlights();
       return;
     }
-    findMatches = computeFindMatches(markdownEditor.value, query);
+
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+    const isCaseSensitive = document.getElementById('find-case').classList.contains('active');
+    const isWholeWord = document.getElementById('find-word').classList.contains('active');
+    const scopeFilter = document.getElementById('find-replace-scope').value;
+    const findInSelection = document.getElementById('find-sel').classList.contains('active');
+
+    try {
+      findMatches = frEngine.executeSearch({
+        query,
+        isRegex,
+        isCaseSensitive,
+        isWholeWord,
+        scopeFilter,
+        findInSelection
+      });
+    } catch (err) {
+      findMatches = [];
+      activeFindIndex = -1;
+      if (errorBox && errorMsg) {
+        errorMsg.textContent = err.message;
+        errorBox.style.display = 'block';
+      }
+    }
+
     if (opts.resetIndex || query !== lastFindQuery) {
       activeFindIndex = findMatches.length ? 0 : -1;
     } else if (activeFindIndex >= findMatches.length) {
@@ -3755,6 +4050,7 @@ This is a fully client-side application. Your content never leaves your browser
     lastFindQuery = query;
     updateFindControls();
     updateFindHighlights();
+    updateHistoryDropdowns();
   }
 
   function selectActiveMatch() {
@@ -3762,6 +4058,17 @@ This is a fully client-side application. Your content never leaves your browser
     const match = findMatches[activeFindIndex];
     markdownEditor.focus();
     markdownEditor.setSelectionRange(match.start, match.end);
+    
+    // Auto-scroll logic if editor cursor is near find-replace panel
+    requestAnimationFrame(() => {
+      const panel = document.getElementById('find-replace-modal');
+      if (!isFrDocked && panel && panel.style.display !== 'none') {
+        const panelRect = panel.getBoundingClientRect();
+        // Check if selection coords intersect
+        // Simplification: if panel is right-aligned, push editor view left if needed,
+        // or just let native setSelectionRange scroll to cursor naturally.
+      }
+    });
   }
 
   function cycleFindMatch(direction) {
@@ -3775,16 +4082,24 @@ This is a fully client-side application. Your content never leaves your browser
 
   function openFindReplaceModal() {
     if (!findReplaceModal || !findReplaceInput) return;
+    
+    if (!frEngine) {
+      frEngine = new FindReplaceEngine(markdownEditor);
+    }
+
     isFindModalOpen = true;
     const selected = markdownEditor.value.slice(markdownEditor.selectionStart, markdownEditor.selectionEnd);
-    if (selected) {
+    if (selected && selected.length < 100) {
       findReplaceInput.value = selected;
     }
-    openAppModal(findReplaceModal, { focusTarget: findReplaceInput, onClose: closeFindReplaceModal });
+
+    findReplaceModal.style.display = 'flex';
+    
     requestAnimationFrame(function() {
       findReplaceInput.focus();
       findReplaceInput.select();
     });
+    
     refreshFindMatches({ resetIndex: true });
     if (findMatches.length) {
       selectActiveMatch();
@@ -3793,7 +4108,14 @@ This is a fully client-side application. Your content never leaves your browser
 
   function closeFindReplaceModal() {
     isFindModalOpen = false;
-    closeAppModal(findReplaceModal);
+    const panel = document.getElementById('find-replace-modal');
+    if (panel) {
+      panel.style.display = 'none';
+      if (isFrDocked) {
+        // Undock and return to body
+        toggleFrDockMode();
+      }
+    }
     findMatches = [];
     activeFindIndex = -1;
     updateFindControls();
@@ -3801,10 +4123,25 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function replaceCurrentMatch() {
-    if (!findMatches.length) return;
+    if (!findMatches.length || activeFindIndex < 0) return;
     const replacement = findReplaceWith ? findReplaceWith.value : '';
     const match = findMatches[activeFindIndex];
-    replaceEditorRange(match.start, match.end, replacement, match.start, match.start + replacement.length);
+
+    const preserveCase = document.getElementById('replace-preserve-case').classList.contains('active');
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+
+    // Syntax validation
+    const scopeFilter = document.getElementById('find-replace-scope').value;
+    if (scopeFilter === 'latex' || scopeFilter === 'mermaid') {
+      const check = validateBlockSyntax(match.value, replacement, scopeFilter);
+      if (!check.valid) {
+        alert(`Blocked replacement: ${check.reason}`);
+        return;
+      }
+    }
+
+    frEngine.executeReplace(match, replacement, { preserveCase, isRegex });
+    
     refreshFindMatches();
     if (findMatches.length) {
       activeFindIndex = Math.min(activeFindIndex, findMatches.length - 1);
@@ -3813,70 +4150,242 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function replaceAllMatches() {
+    if (!findMatches.length) return;
+    
     const query = findReplaceInput ? findReplaceInput.value : '';
-    if (!query) return;
     const replacement = findReplaceWith ? findReplaceWith.value : '';
-    const regex = new RegExp(escapeRegExp(query), 'gi');
-    markdownEditor.value = markdownEditor.value.replace(regex, () => replacement);
-    markdownEditor.dispatchEvent(new Event('input', { bubbles: true }));
+    const showDiff = document.getElementById('find-replace-diff-toggle').checked;
+
+    if (showDiff) {
+      renderDiffPreview();
+      return;
+    }
+
+    executeBulkReplace();
+  }
+
+  function executeBulkReplace() {
+    const replacement = findReplaceWith ? findReplaceWith.value : '';
+    const preserveCase = document.getElementById('replace-preserve-case').classList.contains('active');
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+    
+    // Reverse sorting to replace from bottom up
+    const matchesCopy = [...findMatches];
+    matchesCopy.sort((a, b) => b.start - a.start);
+
+    for (const match of matchesCopy) {
+      frEngine.executeReplace(match, replacement, { preserveCase, isRegex });
+    }
+
     refreshFindMatches({ resetIndex: true });
     if (findMatches.length) {
       selectActiveMatch();
     }
   }
 
-  function openClearFormattingModal() {
-    if (!clearFormattingModal) return;
-    openAppModal(clearFormattingModal, { focusTarget: clearFormattingConfirm || clearFormattingCancel });
-  }
+  function renderDiffPreview() {
+    const container = document.getElementById('find-replace-diff-container');
+    const modal = document.getElementById('find-replace-diff-modal');
+    if (!container || !modal) return;
 
-  function applyClearFormatting() {
-    const stripped = stripBasicMarkdown(markdownEditor.value);
-    replaceEditorRange(0, markdownEditor.value.length, stripped, 0, 0);
-  }
+    const replacement = findReplaceWith ? findReplaceWith.value : '';
+    const preserveCase = document.getElementById('replace-preserve-case').classList.contains('active');
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+
+    const lines = markdownEditor.value.split('\n');
+    const matchesCopy = [...findMatches];
+    matchesCopy.sort((a, b) => b.start - a.start);
+
+    // Draft the replaced value in memory
+    let draftValue = markdownEditor.value;
+    for (const match of matchesCopy) {
+      let finalRepl = replacement;
+      if (isRegex) {
+        finalRepl = frEngine.applyCaptureGroups(match, finalRepl);
+      }
+      if (preserveCase) {
+        finalRepl = frEngine.preserveCase(match.value, finalRepl);
+      }
+      draftValue = draftValue.slice(0, match.start) + finalRepl + draftValue.slice(match.end);
+    }
+
+    const draftLines = draftValue.split('\n');
+
+    container.innerHTML = '';
+    const fragment = document.createDocumentFragment();
+
+    const maxLines = Math.max(lines.length, draftLines.length);
+    for (let i = 0; i < maxLines; i++) {
+      const origLine = lines[i] !== undefined ? lines[i] : null;
+      const newLine = draftLines[i] !== undefined ? draftLines[i] : null;
+
+      if (origLine !== newLine) {
+        if (origLine !== null) {
+          const delLine = document.createElement('div');
+          delLine.className = 'diff-line deletion';
+          delLine.innerHTML = `<span class="diff-line-num">${i + 1}</span><span class="diff-line-content">- ${escapeHtml(origLine)}</span>`;
+          fragment.appendChild(delLine);
+        }
+        if (newLine !== null) {
+          const addLine = document.createElement('div');
+          addLine.className = 'diff-line addition';
+          addLine.innerHTML = `<span class="diff-line-num">${i + 1}</span><span class="diff-line-content">+ ${escapeHtml(newLine)}</span>`;
+          fragment.appendChild(addLine);
+        }
+      } else if (origLine !== null) {
+        // Show context for matching lines to prevent giant blank diff spaces
+        // Show context only if it surrounds a modified line
+        const hasDiffNearby = Array.from({length: 5}, (_, idx) => i - 2 + idx)
+          .some(lineIdx => lines[lineIdx] !== undefined && draftLines[lineIdx] !== undefined && lines[lineIdx] !== draftLines[lineIdx]);
+        
+        if (hasDiffNearby) {
+          const ctxLine = document.createElement('div');
+          ctxLine.className = 'diff-line context';
+          ctxLine.innerHTML = `<span class="diff-line-num">${i + 1}</span><span class="diff-line-content">  ${escapeHtml(origLine)}</span>`;
+          fragment.appendChild(ctxLine);
+        }
+      }
+    }
 
-  function openHelpModal() {
-    if (!helpModal) return;
-    openAppModal(helpModal, { focusTarget: helpModalClose || helpModalCloseIcon });
+    container.appendChild(fragment);
+    openAppModal(modal, {
+      focusTarget: document.getElementById('find-replace-diff-confirm'),
+      onClose: () => closeAppModal(modal)
+    });
   }
 
-  function openAboutModal() {
-    if (!aboutModal) return;
-    openAppModal(aboutModal, { focusTarget: aboutModalClose || aboutModalCloseIcon });
+  function updateHistoryDropdowns() {
+    const select = document.getElementById('find-replace-history');
+    if (!select || !frEngine) return;
+
+    // Preserve the first option
+    select.innerHTML = '<option value="">Recent queries...</option>';
+    
+    frEngine.history.find.forEach(q => {
+      const opt = document.createElement('option');
+      opt.value = q;
+      opt.textContent = q;
+      select.appendChild(opt);
+    });
   }
 
   function initFindReplaceModal() {
-    if (!findReplaceModal || !findReplaceInput) return;
-    findReplaceInput.addEventListener('input', function() {
-      refreshFindMatches({ resetIndex: true });
-    });
-    findReplaceInput.addEventListener('keydown', function(event) {
-      if (event.key === 'Enter') {
-        event.preventDefault();
-        cycleFindMatch(event.shiftKey ? -1 : 1);
+    const modal = document.getElementById('find-replace-modal');
+    if (!modal) return;
+
+    initFindReplacePanelDrag();
+
+    // Toggle options
+    const toggleButtons = ['find-case', 'find-word', 'find-regex', 'find-sel', 'replace-preserve-case', 'find-wrap'];
+    toggleButtons.forEach(id => {
+      const btn = document.getElementById(id);
+      if (btn) {
+        btn.addEventListener('click', () => {
+          const isActive = btn.classList.contains('active');
+          if (isActive) {
+            btn.classList.remove('active');
+            btn.setAttribute('aria-pressed', 'false');
+          } else {
+            btn.classList.add('active');
+            btn.setAttribute('aria-pressed', 'true');
+          }
+          refreshFindMatches({ resetIndex: true });
+        });
       }
     });
-    if (findReplaceWith) {
-      findReplaceWith.addEventListener('input', updateFindControls);
+
+    // History select handler
+    const historySelect = document.getElementById('find-replace-history');
+    if (historySelect) {
+      historySelect.addEventListener('change', () => {
+        if (historySelect.value) {
+          findReplaceInput.value = historySelect.value;
+          refreshFindMatches({ resetIndex: true });
+        }
+      });
     }
-    if (findReplacePrev) {
-      findReplacePrev.addEventListener('click', function() { cycleFindMatch(-1); });
+
+    // Scope select handler
+    const scopeSelect = document.getElementById('find-replace-scope');
+    if (scopeSelect) {
+      scopeSelect.addEventListener('change', () => {
+        refreshFindMatches({ resetIndex: true });
+      });
     }
-    if (findReplaceNext) {
-      findReplaceNext.addEventListener('click', function() { cycleFindMatch(1); });
+
+    // Dock toggle handler
+    const dockBtn = document.getElementById('find-replace-dock');
+    if (dockBtn) {
+      dockBtn.addEventListener('click', toggleFrDockMode);
     }
-    if (findReplaceCurrent) {
-      findReplaceCurrent.addEventListener('click', replaceCurrentMatch);
+
+    // Advanced Drawer Toggle
+    const drawerToggle = document.getElementById('fr-drawer-toggle');
+    const drawerContent = document.getElementById('fr-drawer-content');
+    if (drawerToggle && drawerContent) {
+      drawerToggle.addEventListener('click', () => {
+        const isOpen = drawerContent.style.display === 'flex';
+        if (isOpen) {
+          drawerContent.style.display = 'none';
+          drawerToggle.setAttribute('aria-expanded', 'false');
+          drawerToggle.innerHTML = '<i class="bi bi-chevron-right me-1"></i> Advanced Options';
+        } else {
+          drawerContent.style.display = 'flex';
+          drawerToggle.setAttribute('aria-expanded', 'true');
+          drawerToggle.innerHTML = '<i class="bi bi-chevron-down me-1"></i> Advanced Options';
+        }
+      });
     }
-    if (findReplaceAll) {
-      findReplaceAll.addEventListener('click', replaceAllMatches);
+
+    // Inputs
+    if (findReplaceInput) {
+      findReplaceInput.addEventListener('input', function() {
+        refreshFindMatches({ resetIndex: true });
+      });
+      findReplaceInput.addEventListener('keydown', function(event) {
+        if (event.key === 'Enter') {
+          event.preventDefault();
+          cycleFindMatch(event.shiftKey ? -1 : 1);
+        }
+      });
     }
-    if (findReplaceClose) {
-      findReplaceClose.addEventListener('click', closeFindReplaceModal);
+
+    if (findReplaceWith) {
+      findReplaceWith.addEventListener('input', updateFindControls);
     }
-    if (findReplaceCloseIcon) {
-      findReplaceCloseIcon.addEventListener('click', closeFindReplaceModal);
+
+    // Navigation buttons
+    const prevBtn = document.getElementById('find-prev');
+    const nextBtn = document.getElementById('find-next');
+    if (prevBtn) prevBtn.addEventListener('click', () => cycleFindMatch(-1));
+    if (nextBtn) nextBtn.addEventListener('click', () => cycleFindMatch(1));
+
+    // Action buttons
+    const currentBtn = document.getElementById('find-replace-current');
+    const allBtn = document.getElementById('find-replace-all');
+    if (currentBtn) currentBtn.addEventListener('click', replaceCurrentMatch);
+    if (allBtn) allBtn.addEventListener('click', replaceAllMatches);
+
+    // Close buttons
+    const closeBtn = document.getElementById('find-replace-close');
+    const closeIcon = document.getElementById('find-replace-close-icon');
+    if (closeBtn) closeBtn.addEventListener('click', closeFindReplaceModal);
+    if (closeIcon) closeIcon.addEventListener('click', closeFindReplaceModal);
+
+    // Diff modal confirmation triggers
+    const diffConfirmBtn = document.getElementById('find-replace-diff-confirm');
+    const diffCancelBtn = document.getElementById('find-replace-diff-cancel');
+    const diffCloseIcon = document.getElementById('find-replace-diff-close-icon');
+    const diffModal = document.getElementById('find-replace-diff-modal');
+
+    if (diffConfirmBtn) {
+      diffConfirmBtn.addEventListener('click', () => {
+        executeBulkReplace();
+        closeAppModal(diffModal);
+      });
     }
+    if (diffCancelBtn) diffCancelBtn.addEventListener('click', () => closeAppModal(diffModal));
+    if (diffCloseIcon) diffCloseIcon.addEventListener('click', () => closeAppModal(diffModal));
   }
 
   function initAppModals() {
diff --git a/desktop-app/resources/styles.css b/desktop-app/resources/styles.css
index 2a7ecf2..2e47509 100644
--- a/desktop-app/resources/styles.css
+++ b/desktop-app/resources/styles.css
@@ -1,2948 +1,3377 @@
-:root {
-  --bg-color: #ffffff;
-  --editor-bg: #f6f8fa;
-  --preview-bg: #ffffff; /* Preview background for light mode */
-  --text-color: #24292e;
-  --text-secondary: #57606a;
-  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
-  --color-danger-fg: #d73a49;
-  --preview-text-color: #24292e; /* Text color for preview in light mode */
-  --border-color: #e1e4e8;
-  --header-bg: #f6f8fa;
-  --button-bg: #f6f8fa;
-  --button-hover: #e1e4e8;
-  --button-active: #d1d5da;
-  --scrollbar-thumb: #c1c1c1;
-  --scrollbar-track: #f1f1f1;
-  --accent-color: #0366d6;
-  --table-bg: #ffffff; /* Table background for light mode */
-  --code-bg: #f6f8fa; /* Code block background for light mode */
-}
-
-[data-theme="dark"] {
-  --bg-color: #0d1117;
-  --editor-bg: #161b22;
-  --preview-bg: #0d1117; /* Preview background for dark mode */
-  --text-color: #c9d1d9;
-  --text-secondary: #8b949e;
-  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
-  --color-danger-fg: #f85149;
-  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
-  --border-color: #30363d;
-  --header-bg: #161b22;
-  --button-bg: #21262d;
-  --button-hover: #30363d;
-  --button-active: #3b434b;
-  --scrollbar-thumb: #484f58;
-  --scrollbar-track: #21262d;
-  --accent-color: #58a6ff;
-  --table-bg: #161b22; /* Table background for dark mode */
-  --code-bg: #161b22; /* Code block background for dark mode */
-}
-
-* {
-  box-sizing: border-box;
-  margin: 0;
-  padding: 0;
-}
-
-body {
-  background-color: var(--bg-color);
-  color: var(--text-color);
-  transition: background-color 0.3s ease, color 0.3s ease;
-  min-height: 100vh;
-  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
-}
-
-.app-header {
-  background-color: var(--header-bg);
-  border-bottom: 1px solid var(--border-color);
-  padding: 0.35rem 0.75rem;
-  transition: background-color 0.3s ease;
-  position: relative;
-  z-index: 100;
-  flex-shrink: 0;
-}
-
-.app-container {
-  height: 100vh;
-  display: flex;
-  flex-direction: column;
-  overflow: hidden;
-}
-
-.content-container {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-}
-
-.editor-pane, .preview-pane {
-  flex: 1;
-  padding: 20px;
-  overflow-y: auto;
-  position: relative;
-  transition: background-color 0.3s ease;
-}
-
-.editor-pane {
-  background-color: var(--editor-bg);
-  border-right: 1px solid var(--border-color);
-  padding-right: 0px;
-  --line-number-gutter: 0px;
-}
-
-.preview-pane {
-  background-color: var(--preview-bg); /* Using the new variable for preview background */
-}
-
-/* Custom scrollbar */
-.editor-pane::-webkit-scrollbar,
-.preview-pane::-webkit-scrollbar,
-#markdown-editor::-webkit-scrollbar {
-  width: 8px;
-  height: 8px;
-}
-
-.editor-pane::-webkit-scrollbar-track,
-.preview-pane::-webkit-scrollbar-track,
-#markdown-editor::-webkit-scrollbar-track {
-  background: var(--scrollbar-track);
-}
-
-.editor-pane::-webkit-scrollbar-thumb,
-.preview-pane::-webkit-scrollbar-thumb,
-#markdown-editor::-webkit-scrollbar-thumb {
-  background: var(--scrollbar-thumb);
-  border-radius: 4px;
-}
-
-.editor-pane::-webkit-scrollbar-thumb:hover,
-.preview-pane::-webkit-scrollbar-thumb:hover,
-#markdown-editor::-webkit-scrollbar-thumb:hover {
-  background: var(--button-active);
-}
-
-#markdown-editor {
-  width: 100%;
-  height: 100%;
-  border: none;
-  background-color: transparent;
-  color: var(--text-color);
-  resize: none;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 14px;
-  line-height: 1.5;
-  padding: 10px;
-  padding-left: calc(10px + var(--line-number-gutter));
-  transition: background-color 0.3s ease, color 0.3s ease;
-  overflow-y: auto;
-  position: relative;
-  z-index: 3;
-}
-
-#markdown-editor:focus {
-  outline: none;
-}
-
-.preview-pane {
-  padding: 20px;
-}
-
-.markdown-body {
-  padding: 20px;
-  width: 100%;
-  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
-  color: var(--preview-text-color); /* Using specific text color for preview content */
-}
-
-.markdown-body a.reference-link {
-  font-size: 0.75em;
-  letter-spacing: -0.02em;
-  line-height: 1;
-  vertical-align: super;
-  position: relative;
-  top: 0.08em;
-}
-
-/* Style tables in light mode */
-.markdown-body table {
-  background-color: var(--table-bg);
-  border-color: var(--border-color);
-}
-
-.markdown-body table tr {
-  background-color: var(--table-bg);
-  border-top: 1px solid var(--border-color);
-}
-
-.markdown-body table tr:nth-child(2n) {
-  background-color: var(--bg-color);
-}
-
-/* Style code blocks in light mode */
-.markdown-body pre {
-  background-color: var(--code-bg);
-  border-radius: 6px;
-}
-
-.markdown-body code {
-  background-color: var(--code-bg);
-  border-radius: 3px;
-  padding: 0.2em 0.4em;
-}
-
-.markdown-body img.emoji-inline {
-  width: 1em;
-  height: 1em;
-  vertical-align: -0.1em;
-}
-
-.markdown-body ul,
-.markdown-body ol {
-  padding-left: 2em;
-  margin: 0.4em 0;
-}
-
-.markdown-body ul ul,
-.markdown-body ul ol,
-.markdown-body ol ul,
-.markdown-body ol ol {
-  margin-top: 0.2em;
-  margin-bottom: 0.2em;
-}
-
-.markdown-body ul.contains-task-list,
-.markdown-body li.task-list-item {
-  list-style: none;
-}
-
-.markdown-body ul.contains-task-list {
-  padding-left: 2em;
-}
-
-.markdown-body li.task-list-item input[type="checkbox"] {
-  margin: 0 0.5em 0.2em 0;
-  vertical-align: middle;
-  pointer-events: none;
-}
-
-.markdown-body li.task-list-item::marker {
-  content: "";
-}
-
-.markdown-body li:has(> input[type="checkbox"]) {
-  list-style: none;
-}
-
-.markdown-body li:has(> input[type="checkbox"])::marker {
-  content: "";
-}
-
-.markdown-body ul:has(> li > input[type="checkbox"]) {
-  list-style: none;
-  padding-left: 2em;
-}
-
-.markdown-body .footnotes {
-  margin-top: 1.5rem;
-  font-size: 0.9em;
-}
-
-.markdown-body .footnotes ol {
-  padding-left: 1.5em;
-}
-
-.markdown-body .footnotes ol > li::marker {
-  content: "[" counter(list-item) "] ";
-  font-weight: 600;
-}
-
-.markdown-body .footnotes li > p {
-  margin: 0.2em 0;
-}
-
-.markdown-body .footnote-ref a,
-.markdown-body .footnote-backref {
-  text-decoration: none;
-}
-
-.markdown-body .footnote-backref {
-  margin-left: 0.4em;
-}
-
-.markdown-body .markdown-alert {
-  padding: 0.5rem 1rem;
-  margin-bottom: 16px;
-  border-left: 0.25em solid;
-  border-radius: 0.375rem;
-}
-
-.markdown-body .markdown-alert > :last-child {
-  margin-bottom: 0;
-}
-
-.markdown-body .markdown-alert-title {
-  margin: 0 0 8px;
-  font-weight: 600;
-  line-height: 1.25;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-}
-
-.markdown-body .markdown-alert-icon {
-  display: inline-flex;
-  width: 16px;
-  height: 16px;
-}
-
-.markdown-body .markdown-alert-icon svg {
-  width: 16px;
-  height: 16px;
-  fill: currentColor;
-}
-
-.markdown-body .markdown-alert-note {
-  color: #0969da;
-  border-left-color: #0969da;
-  background-color: #ddf4ff;
-}
-
-.markdown-body .markdown-alert-tip {
-  color: #1a7f37;
-  border-left-color: #1a7f37;
-  background-color: #dafbe1;
-}
-
-.markdown-body .markdown-alert-important {
-  color: #8250df;
-  border-left-color: #8250df;
-  background-color: #fbefff;
-}
-
-.markdown-body .markdown-alert-warning {
-  color: #9a6700;
-  border-left-color: #9a6700;
-  background-color: #fff8c5;
-}
-
-.markdown-body .markdown-alert-caution {
-  color: #cf222e;
-  border-left-color: #cf222e;
-  background-color: #ffebe9;
-}
-
-.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
-  color: var(--preview-text-color);
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-note {
-  color: #4493f8;
-  background-color: rgba(31, 111, 235, 0.15);
-  border-left-color: #4493f8;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-tip {
-  color: #3fb950;
-  background-color: rgba(35, 134, 54, 0.15);
-  border-left-color: #3fb950;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-important {
-  color: #ab7df8;
-  background-color: rgba(137, 87, 229, 0.15);
-  border-left-color: #ab7df8;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-warning {
-  color: #d29922;
-  background-color: rgba(210, 153, 34, 0.18);
-  border-left-color: #d29922;
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-caution {
-  color: #f85149;
-  background-color: rgba(248, 81, 73, 0.18);
-  border-left-color: #f85149;
-}
-
-.toolbar {
-  display: flex;
-  gap: 8px;
-  align-items: center;
-}
-
-.toolbar-group {
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-}
-
-.toolbar-divider {
-  width: 1px;
-  height: 20px;
-  background-color: var(--border-color);
-  opacity: 0.7;
-}
-
-.tool-button {
-  background-color: var(--button-bg);
-  border: 1px solid var(--border-color);
-  color: var(--text-color);
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-  letter-spacing: 0.03em;
-  word-break: keep-all;
-  overflow-wrap: break-word;
-  text-align: justify;
-}
-
-/* Specific heading spacing improvements for CJK characters */
-html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
-html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
-html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
-  font-weight: 700;
-  letter-spacing: 0.02em;
-  margin-top: 1.4em;
-  margin-bottom: 0.6em;
-}
-
-/* Smooth fade and scale transition for dropdown active states */
-.dropdown-menu {
-  opacity: 0;
-  transform: translateY(8px) scale(0.98);
-  display: block;
-  visibility: hidden;
-  transition: opacity 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.2s;
-}
-
-.dropdown-menu.show {
-  opacity: 1;
-  transform: translateY(0) scale(1);
-  visibility: visible;
-}
\ No newline at end of file
+:root {
+  --bg-color: #ffffff;
+  --editor-bg: #f6f8fa;
+  --preview-bg: #ffffff; /* Preview background for light mode */
+  --text-color: #24292e;
+  --text-secondary: #57606a;
+  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
+  --color-danger-fg: #d73a49;
+  --preview-text-color: #24292e; /* Text color for preview in light mode */
+  --border-color: #e1e4e8;
+  --header-bg: #f6f8fa;
+  --button-bg: #f6f8fa;
+  --button-hover: #e1e4e8;
+  --button-active: #d1d5da;
+  --scrollbar-thumb: #c1c1c1;
+  --scrollbar-track: #f1f1f1;
+  --accent-color: #0366d6;
+  --table-bg: #ffffff; /* Table background for light mode */
+  --code-bg: #f6f8fa; /* Code block background for light mode */
+}
+
+[data-theme="dark"] {
+  --bg-color: #0d1117;
+  --editor-bg: #161b22;
+  --preview-bg: #0d1117; /* Preview background for dark mode */
+  --text-color: #c9d1d9;
+  --text-secondary: #8b949e;
+  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
+  --color-danger-fg: #f85149;
+  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
+  --border-color: #30363d;
+  --header-bg: #161b22;
+  --button-bg: #21262d;
+  --button-hover: #30363d;
+  --button-active: #3b434b;
+  --scrollbar-thumb: #484f58;
+  --scrollbar-track: #21262d;
+  --accent-color: #58a6ff;
+  --table-bg: #161b22; /* Table background for dark mode */
+  --code-bg: #161b22; /* Code block background for dark mode */
+}
+
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+body {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  transition: background-color 0.3s ease, color 0.3s ease;
+  min-height: 100vh;
+  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
+}
+
+.app-header {
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  padding: 0.35rem 0.75rem;
+  transition: background-color 0.3s ease;
+  position: relative;
+  z-index: 100;
+  flex-shrink: 0;
+}
+
+.app-container {
+  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+}
+
+.editor-pane, .preview-pane {
+  flex: 1;
+  padding: 20px;
+  overflow-y: auto;
+  position: relative;
+  transition: background-color 0.3s ease;
+}
+
+.editor-pane {
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  padding-right: 0px;
+  --line-number-gutter: 0px;
+}
+
+.preview-pane {
+  background-color: var(--preview-bg); /* Using the new variable for preview background */
+}
+
+/* Custom scrollbar */
+.editor-pane::-webkit-scrollbar,
+.preview-pane::-webkit-scrollbar,
+#markdown-editor::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-pane::-webkit-scrollbar-track,
+.preview-pane::-webkit-scrollbar-track,
+#markdown-editor::-webkit-scrollbar-track {
+  background: var(--scrollbar-track);
+}
+
+.editor-pane::-webkit-scrollbar-thumb,
+.preview-pane::-webkit-scrollbar-thumb,
+#markdown-editor::-webkit-scrollbar-thumb {
+  background: var(--scrollbar-thumb);
+  border-radius: 4px;
+}
+
+.editor-pane::-webkit-scrollbar-thumb:hover,
+.preview-pane::-webkit-scrollbar-thumb:hover,
+#markdown-editor::-webkit-scrollbar-thumb:hover {
+  background: var(--button-active);
+}
+
+#markdown-editor {
+  width: 100%;
+  height: 100%;
+  border: none;
+  background-color: transparent;
+  color: var(--text-color);
+  resize: none;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  padding: 10px;
+  padding-left: calc(10px + var(--line-number-gutter));
+  transition: background-color 0.3s ease, color 0.3s ease;
+  overflow-y: auto;
+  position: relative;
+  z-index: 3;
+}
+
+#markdown-editor:focus {
+  outline: none;
+}
+
+.preview-pane {
+  padding: 20px;
+}
+
+.markdown-body {
+  padding: 20px;
+  width: 100%;
+  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
+  color: var(--preview-text-color); /* Using specific text color for preview content */
+}
+
+.markdown-body a.reference-link {
+  font-size: 0.75em;
+  letter-spacing: -0.02em;
+  line-height: 1;
+  vertical-align: super;
+  position: relative;
+  top: 0.08em;
+}
+
+/* Style tables in light mode */
+.markdown-body table {
+  background-color: var(--table-bg);
+  border-color: var(--border-color);
+}
+
+.markdown-body table tr {
+  background-color: var(--table-bg);
+  border-top: 1px solid var(--border-color);
+}
+
+.markdown-body table tr:nth-child(2n) {
+  background-color: var(--bg-color);
+}
+
+/* Style code blocks in light mode */
+.markdown-body pre {
+  background-color: var(--code-bg);
+  border-radius: 6px;
+}
+
+.markdown-body code {
+  background-color: var(--code-bg);
+  border-radius: 3px;
+  padding: 0.2em 0.4em;
+}
+
+.markdown-body img.emoji-inline {
+  width: 1em;
+  height: 1em;
+  vertical-align: -0.1em;
+}
+
+.markdown-body ul,
+.markdown-body ol {
+  padding-left: 2em;
+  margin: 0.4em 0;
+}
+
+.markdown-body ul ul,
+.markdown-body ul ol,
+.markdown-body ol ul,
+.markdown-body ol ol {
+  margin-top: 0.2em;
+  margin-bottom: 0.2em;
+}
+
+.markdown-body ul.contains-task-list,
+.markdown-body li.task-list-item {
+  list-style: none;
+}
+
+.markdown-body ul.contains-task-list {
+  padding-left: 2em;
+}
+
+.markdown-body li.task-list-item input[type="checkbox"] {
+  margin: 0 0.5em 0.2em 0;
+  vertical-align: middle;
+  pointer-events: none;
+}
+
+.markdown-body li.task-list-item::marker {
+  content: "";
+}
+
+.markdown-body li:has(> input[type="checkbox"]) {
+  list-style: none;
+}
+
+.markdown-body li:has(> input[type="checkbox"])::marker {
+  content: "";
+}
+
+.markdown-body ul:has(> li > input[type="checkbox"]) {
+  list-style: none;
+  padding-left: 2em;
+}
+
+.markdown-body .footnotes {
+  margin-top: 1.5rem;
+  font-size: 0.9em;
+}
+
+.markdown-body .footnotes ol {
+  padding-left: 1.5em;
+}
+
+.markdown-body .footnotes ol > li::marker {
+  content: "[" counter(list-item) "] ";
+  font-weight: 600;
+}
+
+.markdown-body .footnotes li > p {
+  margin: 0.2em 0;
+}
+
+.markdown-body .footnote-ref a,
+.markdown-body .footnote-backref {
+  text-decoration: none;
+}
+
+.markdown-body .footnote-backref {
+  margin-left: 0.4em;
+}
+
+.markdown-body .markdown-alert {
+  padding: 0.5rem 1rem;
+  margin-bottom: 16px;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.markdown-body .markdown-alert > :last-child {
+  margin-bottom: 0;
+}
+
+.markdown-body .markdown-alert-title {
+  margin: 0 0 8px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.markdown-body .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.markdown-body .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.markdown-body .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.markdown-body .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.markdown-body .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.markdown-body .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.markdown-body .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--preview-text-color);
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-note {
+  color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+  border-left-color: #4493f8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-tip {
+  color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+  border-left-color: #3fb950;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-important {
+  color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+  border-left-color: #ab7df8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-warning {
+  color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+  border-left-color: #d29922;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-caution {
+  color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+  border-left-color: #f85149;
+}
+
+.toolbar {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.toolbar-group {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+}
+
+.toolbar-divider {
+  width: 1px;
+  height: 20px;
+  background-color: var(--border-color);
+  opacity: 0.7;
+}
+
+.tool-button {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 5px;
+  padding: 4px 8px;
+  font-size: 13px;
+  cursor: pointer;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  transition: all 0.2s ease;
+}
+
+.tool-button:hover {
+  background-color: var(--button-hover);
+}
+
+.tool-button:active {
+  background-color: var(--button-active);
+}
+
+.tool-button:disabled,
+.tool-button[aria-disabled="true"] {
+  cursor: not-allowed;
+  opacity: 0.5;
+}
+
+.tool-button i {
+  font-size: 15px;
+}
+
+.tool-button.is-active,
+.tool-button.is-active:hover {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: rgba(3, 102, 214, 0.08);
+}
+
+.btn-text {
+  display: none;
+}
+
+.toolbar .tool-button {
+  height: 28px;
+  min-width: 28px;
+}
+
+.toolbar .tool-button.sync-active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+}
+
+.file-input {
+  display: none;
+}
+
+/* Drag overlay: full-screen drop target shown when user drags a file over the window */
+.drag-overlay {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 9999;
+  background-color: rgba(0, 0, 0, 0.45);
+  pointer-events: none;
+  align-items: center;
+  justify-content: center;
+}
+
+.drag-overlay.active {
+  display: flex;
+  pointer-events: auto;
+}
+
+.drag-overlay-inner {
+  border: 3px dashed var(--accent-color);
+  border-radius: 12px;
+  padding: 48px 64px;
+  text-align: center;
+  color: #ffffff;
+  background-color: rgba(3, 102, 214, 0.15);
+  animation: overlayPulse 1.4s ease-in-out infinite;
+}
+
+.drag-overlay-icon {
+  display: block;
+  font-size: 3rem;
+  margin-bottom: 12px;
+  color: var(--accent-color);
+}
+
+.drag-overlay-text {
+  font-size: 1.4rem;
+  font-weight: 600;
+  margin-bottom: 4px;
+}
+
+.drag-overlay-sub {
+  font-size: 0.85rem;
+  opacity: 0.75;
+  margin-bottom: 0;
+}
+
+@keyframes overlayPulse {
+  0%, 100% { transform: scale(1); }
+  50% { transform: scale(1.015); }
+}
+
+/* Editor drop hint: subtle text at bottom of editor pane, shown only when empty */
+.drop-hint {
+  position: absolute;
+  bottom: 14px;
+  left: 0;
+  right: 0;
+  text-align: center;
+  font-size: 0.75rem;
+  color: var(--text-color);
+  opacity: 0.35;
+  pointer-events: none;
+  user-select: none;
+  z-index: 3;
+}
+
+.editor-pane:has(#markdown-editor:not(:placeholder-shown)) .drop-hint {
+  display: none;
+}
+
+.line-numbers {
+  position: absolute;
+  top: 20px;
+  bottom: 20px;
+  left: 20px;
+  width: var(--line-number-gutter);
+  padding: 10px 8px 10px 0;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  text-align: right;
+  color: var(--text-color);
+  opacity: 0.55;
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  box-sizing: border-box;
+  overflow: hidden;
+  pointer-events: none;
+  user-select: none;
+  z-index: 2;
+  font-variant-numeric: tabular-nums;
+}
+
+.line-numbers .line-number {
+  display: block;
+  height: auto;
+}
+
+.editor-highlight-layer {
+  position: absolute;
+  inset: 20px 0 20px calc(20px + var(--line-number-gutter));
+  padding: 10px;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+  color: transparent;
+  pointer-events: none;
+  overflow: auto;
+  background-color: var(--editor-bg);
+  border-radius: 4px;
+  z-index: 1;
+}
+
+.editor-highlight-layer::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-thumb {
+  background: transparent;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+.find-highlight {
+  background-color: rgba(255, 196, 0, 0.35);
+  border-radius: 2px;
+}
+
+.find-highlight.active {
+  background-color: rgba(255, 196, 0, 0.65);
+}
+
+/* Dropdown improvements */
+.dropdown-menu {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+}
+
+.dropdown-item {
+  color: var(--text-color);
+}
+
+.dropdown-item:hover, .dropdown-item:focus {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+/* Markdown formatting toolbar */
+.markdown-format-toolbar {
+  display: flex;
+  align-items: center;
+  height: 34px;
+  padding: 0 6px;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  overflow-x: auto;
+  overflow-y: hidden;
+  flex-shrink: 0;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.markdown-format-toolbar::-webkit-scrollbar {
+  display: none;
+}
+
+.markdown-toolbar-group {
+  display: flex;
+  align-items: center;
+  gap: 2px;
+  height: 100%;
+  padding: 0 6px;
+  border-right: 1px solid var(--border-color);
+  flex-shrink: 0;
+}
+
+.markdown-toolbar-group:first-child {
+  padding-left: 0;
+}
+
+.markdown-toolbar-group:last-child {
+  border-right: none;
+  padding-right: 0;
+}
+
+.markdown-tool-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 26px;
+  height: 26px;
+  border: 1px solid transparent;
+  border-radius: 4px;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 14px;
+  line-height: 1;
+  padding: 0;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.markdown-tool-btn:hover,
+.markdown-tool-btn:focus-visible {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+}
+
+.markdown-tool-btn:active {
+  background-color: var(--button-active);
+}
+
+.markdown-tool-btn i {
+  font-size: 15px;
+}
+
+.markdown-tool-btn[data-md-action="reference"] i::before {
+  content: "[ ]";
+  font-style: normal;
+  font-size: 12px;
+  letter-spacing: -0.12em;
+}
+
+.markdown-tool-btn.text-tool {
+  width: auto;
+  min-width: 26px;
+  padding: 0 5px;
+  font-weight: 600;
+  font-family: Georgia, "Times New Roman", serif;
+}
+
+.heading-group .markdown-tool-btn {
+  min-width: 30px;
+}
+
+
+
+/* Loading indicators */
+.loading {
+  opacity: 0.6;
+  pointer-events: none;
+}
+
+/* Focus outline for accessibility */
+button:focus, 
+a:focus {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+/* Animation for copied message */
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+/* Tooltip styles */
+.tooltip {
+  position: absolute;
+  background: var(--button-bg);
+  border: 1px solid var(--border-color);
+  padding: 5px 8px;
+  border-radius: 4px;
+  font-size: 12px;
+  z-index: 1000;
+  animation: fadeIn 0.2s ease;
+}
+
+/* Styles for GitHub markdown preview light mode */
+.markdown-body {
+  color-scheme: light;
+  --color-prettylights-syntax-comment: #6a737d;
+  --color-prettylights-syntax-constant: #005cc5;
+  --color-prettylights-syntax-entity: #6f42c1;
+  --color-prettylights-syntax-storage-modifier-import: #24292e;
+  --color-prettylights-syntax-entity-tag: #22863a;
+  --color-prettylights-syntax-keyword: #d73a49;
+  --color-prettylights-syntax-string: #032f62;
+  --color-prettylights-syntax-variable: #e36209;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #b31d28;
+  --color-prettylights-syntax-invalid-illegal-text: #fafbfc;
+  --color-prettylights-syntax-invalid-illegal-bg: #b31d28;
+  --color-prettylights-syntax-carriage-return-text: #fafbfc;
+  --color-prettylights-syntax-carriage-return-bg: #d73a49;
+  --color-prettylights-syntax-string-regexp: #22863a;
+  --color-prettylights-syntax-markup-list: #735c0f;
+  --color-prettylights-syntax-markup-heading: #005cc5;
+  --color-prettylights-syntax-markup-italic: #24292e;
+  --color-prettylights-syntax-markup-bold: #24292e;
+  --color-prettylights-syntax-markup-deleted-text: #b31d28;
+  --color-prettylights-syntax-markup-deleted-bg: #ffeef0;
+  --color-prettylights-syntax-markup-inserted-text: #22863a;
+  --color-prettylights-syntax-markup-inserted-bg: #f0fff4;
+  --color-prettylights-syntax-markup-changed-text: #e36209;
+  --color-prettylights-syntax-markup-changed-bg: #ffebda;
+  --color-prettylights-syntax-markup-ignored-text: #f6f8fa;
+  --color-prettylights-syntax-markup-ignored-bg: #005cc5;
+  --color-prettylights-syntax-meta-diff-range: #6f42c1;
+  --color-prettylights-syntax-brackethighlighter-angle: #586069;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #e1e4e8;
+  --color-prettylights-syntax-constant-other-reference-link: #032f62;
+  --color-fg-default: #24292e;
+  --color-fg-muted: #586069;
+  --color-fg-subtle: #6a737d;
+  --color-canvas-default: #ffffff;
+  --color-canvas-subtle: #f6f8fa;
+  --color-border-default: #e1e4e8;
+  --color-border-muted: #eaecef;
+  --color-neutral-muted: rgba(175,184,193,0.2);
+  --color-accent-fg: #0366d6;
+  --color-accent-emphasis: #0366d6;
+  --color-attention-subtle: #fff5b1;
+  --color-danger-fg: #d73a49;
+}
+
+/* Styles for GitHub markdown preview dark mode */
+[data-theme="dark"] .markdown-body {
+  color-scheme: dark;
+  --color-prettylights-syntax-comment: #8b949e;
+  --color-prettylights-syntax-constant: #79c0ff;
+  --color-prettylights-syntax-entity: #d2a8ff;
+  --color-prettylights-syntax-storage-modifier-import: #c9d1d9;
+  --color-prettylights-syntax-entity-tag: #7ee787;
+  --color-prettylights-syntax-keyword: #ff7b72;
+  --color-prettylights-syntax-string: #a5d6ff;
+  --color-prettylights-syntax-variable: #ffa657;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #f85149;
+  --color-prettylights-syntax-invalid-illegal-text: #f0f6fc;
+  --color-prettylights-syntax-invalid-illegal-bg: #8e1519;
+  --color-prettylights-syntax-carriage-return-text: #f0f6fc;
+  --color-prettylights-syntax-carriage-return-bg: #b62324;
+  --color-prettylights-syntax-string-regexp: #7ee787;
+  --color-prettylights-syntax-markup-list: #f2cc60;
+  --color-prettylights-syntax-markup-heading: #1f6feb;
+  --color-prettylights-syntax-markup-italic: #c9d1d9;
+  --color-prettylights-syntax-markup-bold: #c9d1d9;
+  --color-prettylights-syntax-markup-deleted-text: #ffdcd7;
+  --color-prettylights-syntax-markup-deleted-bg: #67060c;
+  --color-prettylights-syntax-markup-inserted-text: #aff5b4;
+  --color-prettylights-syntax-markup-inserted-bg: #033a16;
+  --color-prettylights-syntax-markup-changed-text: #ffdfb6;
+  --color-prettylights-syntax-markup-changed-bg: #5a1e02;
+  --color-prettylights-syntax-markup-ignored-text: #c9d1d9;
+  --color-prettylights-syntax-markup-ignored-bg: #1158c7;
+  --color-prettylights-syntax-meta-diff-range: #d2a8ff;
+  --color-prettylights-syntax-brackethighlighter-angle: #8b949e;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #484f58;
+  --color-prettylights-syntax-constant-other-reference-link: #a5d6ff;
+  --color-fg-default: #c9d1d9;
+  --color-fg-muted: #8b949e;
+  --color-fg-subtle: #484f58;
+  --color-canvas-default: #0d1117;
+  --color-canvas-subtle: #161b22;
+  --color-border-default: #30363d;
+  --color-border-muted: #21262d;
+  --color-neutral-muted: rgba(110,118,129,0.4);
+  --color-accent-fg: #58a6ff;
+  --color-accent-emphasis: #1f6feb;
+  --color-attention-subtle: rgba(187,128,9,0.15);
+  --color-danger-fg: #f85149;
+}
+
+/* Override specific styles for dark mode tables and code */
+[data-theme="dark"] .markdown-body table tr {
+  background-color: var(--table-bg);
+}
+
+[data-theme="dark"] .markdown-body table tr:nth-child(2n) {
+  background-color: #1c2128; /* Slightly lighter than base dark background */
+}
+
+[data-theme="dark"] .markdown-body pre {
+  background-color: var(--code-bg);
+}
+
+[data-theme="dark"] .markdown-body code {
+  background-color: var(--code-bg);
+}
+
+/* Syntax Highlighting Mapping to GitHub Variables */
+.hljs {
+  color: var(--color-fg-default);
+}
+.hljs-doctag,
+.hljs-keyword,
+.hljs-meta .hljs-keyword,
+.hljs-template-tag,
+.hljs-template-variable,
+.hljs-type,
+.hljs-variable.language_ {
+  color: var(--color-prettylights-syntax-keyword);
+}
+.hljs-title,
+.hljs-title.class_,
+.hljs-title.class_.inherited__,
+.hljs-title.function_ {
+  color: var(--color-prettylights-syntax-entity);
+}
+.hljs-attr,
+.hljs-attribute,
+.hljs-literal,
+.hljs-meta,
+.hljs-number,
+.hljs-operator,
+.hljs-variable,
+.hljs-selector-attr,
+.hljs-selector-class,
+.hljs-selector-id {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-regexp,
+.hljs-string,
+.hljs-meta .hljs-string {
+  color: var(--color-prettylights-syntax-string);
+}
+.hljs-built_in,
+.hljs-symbol {
+  color: var(--color-prettylights-syntax-variable);
+}
+.hljs-comment,
+.hljs-code,
+.hljs-formula {
+  color: var(--color-prettylights-syntax-comment);
+}
+.hljs-name,
+.hljs-quote,
+.hljs-selector-tag,
+.hljs-selector-pseudo {
+  color: var(--color-prettylights-syntax-entity-tag);
+}
+.hljs-subst {
+  color: var(--color-fg-default);
+}
+.hljs-section {
+  color: var(--color-prettylights-syntax-markup-heading);
+  font-weight: bold;
+}
+.hljs-bullet {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-emphasis {
+  color: var(--color-fg-default);
+  font-style: italic;
+}
+.hljs-strong {
+  color: var(--color-fg-default);
+  font-weight: bold;
+}
+.hljs-addition {
+  color: var(--color-prettylights-syntax-markup-inserted-text);
+  background-color: var(--color-prettylights-syntax-markup-inserted-bg);
+}
+.hljs-deletion {
+  color: var(--color-prettylights-syntax-markup-deleted-text);
+  background-color: var(--color-prettylights-syntax-markup-deleted-bg);
+}
+
+.stats-container {
+  font-size: 0.8rem;
+  color: var(--text-color);
+}
+
+.stat-item {
+  align-items: center;
+}
+
+.stat-item i {
+  font-size: 0.9rem;
+  opacity: 0.8;
+}
+
+#importDropdown,
+#exportDropdown,
+#languageDropdown {
+  font-size: 0.8rem;
+}
+
+#importDropdown i,
+#exportDropdown i,
+#languageDropdown i {
+  font-size: 0.9rem;
+}
+
+/* Ensure desktop dropdown menu options match the stats-container font size */
+[aria-labelledby="importDropdown"] .dropdown-item,
+[aria-labelledby="exportDropdown"] .dropdown-item,
+[aria-labelledby="languageDropdown"] .dropdown-item {
+  font-size: 0.8rem;
+}
+
+/* Ensure mobile menu import, export, and language dropdown triggers/options match the mobile stats-container font size */
+#mobile-import-button,
+#mobile-import-github-button,
+#mobile-export-md,
+#mobile-export-html,
+#mobile-export-pdf,
+#mobileLanguageDropdown {
+  font-size: 0.9rem !important;
+}
+
+[aria-labelledby="mobileLanguageDropdown"] .dropdown-item {
+  font-size: 0.9rem;
+}
+
+.editor-pane {
+  overflow: hidden;
+}
+
+/* Mobile Menu Styles */
+.mobile-menu {
+  display: none;
+  position: relative;
+  z-index: 1001;
+}
+
+
+
+/* slide‑in panel */
+.mobile-menu-panel {
+  position: fixed;
+  top: 0;
+  right: -300px;
+  width: 280px;
+  height: 100vh;
+  background-color: var(--bg-color);
+  box-shadow: -2px 0 10px rgba(0, 0, 0, 0.2);
+  transition: right 0.3s ease;
+  overflow-y: auto;
+  padding: 1rem;
+  display: flex;
+  flex-direction: column;
+  z-index: 1002;
+}
+
+.mobile-menu-panel.active {
+  right: 0;
+}
+
+/* translucent overlay behind panel */
+.mobile-menu-overlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100vh;
+  background-color: rgba(0, 0, 0, 0.5);
+  opacity: 0;
+  visibility: hidden;
+  pointer-events: none;
+  transition: opacity 0.3s ease, visibility 0.3s ease;
+  z-index: 1000;
+}
+
+.mobile-menu-overlay.active {
+  opacity: 1;
+  visibility: visible;
+  pointer-events: auto;
+}
+
+/* header inside mobile menu */
+.mobile-menu-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 1rem;
+}
+
+.mobile-menu-header h5 {
+  margin: 0;
+  font-size: 1.25rem;
+  color: var(--text-color);
+}
+
+/* stats section in mobile menu */
+.mobile-stats-container {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+  margin-bottom: 1rem;
+}
+
+.mobile-stats-container .stat-item {
+  font-size: 0.9rem;
+  color: var(--text-color);
+  display: flex;
+  align-items: center;
+}
+
+.mobile-stats-container .stat-item i {
+  margin-right: 0.5em;
+  opacity: 0.8;
+}
+
+/* menu buttons list */
+.mobile-menu-items {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  flex-grow: 1;
+}
+
+/* each menu item */
+.mobile-menu-item {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 6px;
+  padding: 0.6rem 1rem;
+  font-size: 1rem;
+  text-align: left;
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  transition: background-color 0.2s ease;
+  cursor: pointer;
+}
+
+.mobile-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-menu-item:active {
+  background-color: var(--button-active);
+}
+
+/* close button override */
+#close-mobile-menu.tool-button {
+  padding: 0.25rem 0.5rem;
+  font-size: 1rem;
+}
+
+/* Mobile document tabs section */
+.mobile-tabs-section {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-tabs-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 0.5rem;
+}
+
+.mobile-tabs-label {
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--text-color);
+  opacity: 0.8;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+.mobile-new-tab-btn {
+  background: none;
+  border: 1px solid var(--border-color);
+  border-radius: 4px;
+  color: var(--text-color);
+  padding: 2px 7px;
+  font-size: 0.9rem;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.15s ease;
+}
+
+.mobile-new-tab-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-list {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  max-height: 180px;
+  overflow-y: auto;
+}
+
+.mobile-tab-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  padding: 0.45rem 0.75rem;
+  font-size: 0.9rem;
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+  gap: 0.5rem;
+}
+
+.mobile-tab-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-item.active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: var(--bg-color);
+}
+
+.mobile-tab-title {
+  flex: 1;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  min-width: 0;
+}
+
+.mobile-tab-item .tab-menu-btn {
+  opacity: 0.6;
+}
+
+.mobile-tab-item:hover .tab-menu-btn,
+.mobile-tab-item.active .tab-menu-btn {
+  opacity: 0.8;
+}
+
+#mobile-tab-reset-btn {
+  margin-left: 0;
+  height: auto;
+  padding: 0.45rem 0.75rem;
+  justify-content: center;
+  font-size: 0.9rem;
+}
+
+/* ==========================================
+   NAVBAR RESPONSIVE BREAKPOINTS
+   >= 1080px : full desktop navbar
+   <  1080px : mobile hamburger + stacked panes
+   ========================================== */
+
+/* Mobile / tablet (< 1080px): switch to hamburger, stack panes */
+@media (max-width: 1079px) {
+  /* Override Bootstrap d-md-flex / d-md-none so the breakpoint is 1080px */
+  .stats-container,
+  .toolbar {
+    display: none !important;
+  }
+
+  /* Expand touch target sizes to meet WCAG mobile guidelines */
+  .markdown-tool-btn {
+    width: 36px !important;
+    height: 36px !important;
+    font-size: 16px !important;
+  }
+  .markdown-format-toolbar {
+    height: 44px !important;
+  }
+  .tab-close-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+  .tab-menu-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+
+  .mobile-menu {
+    display: block !important;
+  }
+
+  /* Stack editor and preview vertically */
+  .content-container {
+    flex-direction: column;
+  }
+
+  .editor-pane,
+  .preview-pane {
+    flex: none;
+    height: 50%;
+    border-right: none;
+  }
+
+  .editor-pane {
+    border-bottom: 1px solid var(--border-color);
+  }
+
+  /* Hide drag-resize divider (touch devices don't use it) */
+  .resize-divider {
+    display: none;
+  }
+
+  /* Single-pane view modes: occupy full height */
+  .content-container.view-editor-only .editor-pane,
+  .content-container.view-preview-only .preview-pane {
+    height: 100%;
+  }
+
+  .content-container.view-split .editor-pane,
+  .content-container.view-split .preview-pane {
+    height: 50%;
+  }
+}
+
+.github-link {
+  color: var(--text-color);
+  text-decoration: none;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: transform 0.2s ease, color 0.2s ease;
+  margin-right: 2rem;
+}
+
+.github-link:hover {
+  color: var(--accent-color);
+  transform: scale(1.1);
+}
+
+.github-link i {
+  font-size: 1.25rem;
+}
+
+/* ========================================
+   HEADER LAYOUT
+   ======================================== */
+.header-container {
+  position: relative;
+  min-height: 30px;
+}
+
+.app-header h1 {
+  font-size: 1.05rem;
+  line-height: 1.1;
+}
+
+.header-left {
+  flex: 1 0 auto;
+  justify-content: flex-start;
+  white-space: nowrap;
+}
+
+.header-right {
+  flex: 1 0 auto;
+  justify-content: flex-end;
+  white-space: nowrap;
+}
+
+/* Pane View States */
+.content-container.view-editor-only .preview-pane {
+  display: none;
+}
+
+.content-container.view-editor-only .editor-pane {
+  flex: 1;
+  border-right: none;
+}
+
+.content-container.view-preview-only .editor-pane {
+  display: none;
+}
+
+.content-container.view-preview-only .preview-pane {
+  flex: 1;
+}
+
+.content-container.view-split .editor-pane,
+.content-container.view-split .preview-pane {
+  flex: 1;
+}
+
+/* Compact desktop (< 1280px): compact toolbar */
+@media (max-width: 1280px) {
+  /* Compact toolbar at medium widths */
+  .toolbar {
+    gap: 4px;
+  }
+}
+
+
+
+/* ========================================
+   RESIZE DIVIDER - Story 1.3
+   ======================================== */
+
+.resize-divider {
+  width: 8px;
+  background-color: transparent;
+  cursor: col-resize;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+  position: relative;
+  z-index: 10;
+  transition: background-color 0.2s ease;
+}
+
+.resize-divider:hover {
+  background-color: var(--button-hover);
+}
+
+.resize-divider.dragging {
+  background-color: var(--accent-color);
+}
+
+.resize-divider-handle {
+  width: 2px;
+  height: 40px;
+  background-color: var(--border-color);
+  border-radius: 2px;
+  transition: background-color 0.2s ease, width 0.2s ease;
+}
+
+.resize-divider:hover .resize-divider-handle,
+.resize-divider.dragging .resize-divider-handle {
+  background-color: var(--accent-color);
+  width: 3px;
+}
+
+/* Hide divider in single-pane modes */
+.content-container.view-editor-only .resize-divider,
+.content-container.view-preview-only .resize-divider {
+  display: none;
+}
+
+
+
+/* Prevent text selection during drag */
+.resizing {
+  user-select: none;
+  cursor: col-resize !important;
+}
+
+.resizing * {
+  cursor: col-resize !important;
+}
+
+.resizing #markdown-preview,
+.resizing #markdown-editor,
+.resizing .line-numbers {
+  pointer-events: none !important;
+}
+
+/* ========================================
+   MOBILE VIEW MODE CONTROLS - Story 1.4
+   ======================================== */
+
+.mobile-view-mode-group {
+  display: flex;
+  gap: 0;
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-view-mode-btn {
+  flex: 1;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  padding: 8px 12px;
+  font-size: 14px;
+  cursor: pointer;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  transition: all 0.2s ease;
+}
+
+.mobile-view-mode-btn:first-child {
+  border-radius: 6px 0 0 6px;
+}
+
+.mobile-view-mode-btn:last-child {
+  border-radius: 0 6px 6px 0;
+}
+
+.mobile-view-mode-btn:not(:last-child) {
+  border-right: none;
+}
+
+.mobile-view-mode-btn:hover,
+.mobile-view-mode-btn:active {
+  background-color: var(--button-hover);
+}
+
+.mobile-view-mode-btn.active {
+  background-color: var(--button-bg);
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  border-width: 2px;
+  padding: 7px 11px;
+}
+
+.mobile-view-mode-btn.active:not(:last-child) {
+  border-right: 2px solid var(--accent-color);
+}
+
+.mobile-view-mode-btn i {
+  font-size: 18px;
+}
+
+.mobile-view-mode-btn span {
+  font-size: 12px;
+}
+
+/* ========================================
+   RESPONSIVE VIEW MODE FIXES - Story 1.5
+   ======================================== */
+
+
+
+/* ========================================
+   PDF EXPORT TABLE FIX - Rowspan/Colspan
+   ======================================== */
+
+/* Fix for html2canvas not properly rendering rowspan/colspan cells.
+   Apply backgrounds to cells instead of rows to prevent row backgrounds
+   from painting over rowspan cells during canvas capture. */
+.pdf-export table tr {
+  background-color: transparent !important;
+}
+
+.pdf-export table th,
+.pdf-export table td {
+  background-color: var(--table-bg, #ffffff);
+  position: relative;
+}
+
+.pdf-export table tr:nth-child(2n) th,
+.pdf-export table tr:nth-child(2n) td {
+  background-color: var(--bg-color, #f6f8fa);
+}
+
+/* Ensure rowspan cells render correctly */
+.pdf-export table th[rowspan],
+.pdf-export table td[rowspan] {
+  vertical-align: middle;
+  background-color: var(--table-bg, #ffffff) !important;
+}
+
+/* Ensure colspan cells render correctly */
+.pdf-export table th[colspan],
+.pdf-export table td[colspan] {
+  text-align: center;
+}
+
+/* Dark mode PDF export table fix */
+[data-theme="dark"] .pdf-export table th,
+[data-theme="dark"] .pdf-export table td {
+  background-color: var(--table-bg, #161b22);
+}
+
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) th,
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) td {
+  background-color: #1c2128;
+}
+
+[data-theme="dark"] .pdf-export table th[rowspan],
+[data-theme="dark"] .pdf-export table td[rowspan] {
+  background-color: var(--table-bg, #161b22) !important;
+}
+
+/* ========================================
+   MERMAID DIAGRAM TOOLBAR
+   ======================================== */
+
+.mermaid-container {
+  position: relative;
+}
+
+.mermaid-toolbar {
+  position: absolute;
+  top: 8px;
+  right: 8px;
+  display: flex;
+  gap: 4px;
+  opacity: 0;
+  transition: opacity 0.2s ease;
+  z-index: 10;
+}
+
+.mermaid-container:hover .mermaid-toolbar {
+  opacity: 1;
+}
+
+.mermaid-toolbar-btn {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 4px;
+  padding: 4px 7px;
+  font-size: 13px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  gap: 3px;
+  transition: background-color 0.2s ease, color 0.2s ease;
+  white-space: nowrap;
+}
+
+.mermaid-toolbar-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--accent-color);
+}
+
+.mermaid-toolbar-btn:active {
+  background-color: var(--button-active);
+}
+
+.mermaid-toolbar-btn i {
+  font-size: 14px;
+}
+
+/* ========================================
+   MERMAID ZOOM MODAL
+   ======================================== */
+
+#mermaid-zoom-modal {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 2000;
+  background-color: rgba(0, 0, 0, 0.75);
+  align-items: center;
+  justify-content: center;
+}
+
+#mermaid-zoom-modal.active {
+  display: flex;
+}
+
+.mermaid-modal-content {
+  background-color: var(--bg-color);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  padding: 16px;
+  width: 85vw;
+  height: 85vh;
+  max-width: 85vw;
+  max-height: 85vh;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+@media (max-width: 576px) {
+  .mermaid-modal-content {
+    width: 95vw;
+    height: 90vh;
+    max-width: 95vw;
+    max-height: 90vh;
+    padding: 10px;
+  }
+}
+
+.mermaid-modal-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.mermaid-modal-header span {
+  font-weight: 600;
+  font-size: 15px;
+  color: var(--text-color);
+}
+
+.mermaid-modal-close {
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 1.2rem;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.2s ease;
+}
+
+.mermaid-modal-close:hover {
+  background-color: var(--button-hover);
+}
+
+.mermaid-modal-diagram {
+  overflow: auto;
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 200px;
+  cursor: grab;
+}
+
+.mermaid-modal-diagram.dragging {
+  cursor: grabbing;
+}
+
+.mermaid-modal-diagram svg {
+  transform-origin: center;
+  transition: transform 0.1s ease;
+  max-width: none;
+}
+
+.mermaid-modal-controls {
+  display: flex;
+  justify-content: center;
+  gap: 8px;
+  flex-wrap: wrap;
+}
+
+.mermaid-modal-controls .mermaid-toolbar-btn {
+  opacity: 1;
+}
+
+/* ========================================
+   DOCUMENT TABS & SESSION MANAGEMENT
+   ======================================== */
+
+.tab-bar {
+  display: flex;
+  align-items: center;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  height: 32px;
+  overflow: visible;  /* ← was: overflow: hidden */
+  flex-shrink: 0;
+  padding: 0 4px;
+  gap: 0;
+  user-select: none;
+  position: relative;
+  z-index: 10;
+}
+
+.tab-list {
+  display: flex;
+  align-items: flex-end;
+  overflow-x: auto;
+  overflow-y: visible;  /* ← was: overflow-y: hidden */
+  flex: 1;
+  height: 100%;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.tab-list::-webkit-scrollbar {
+  display: none;
+}
+
+.tab-item {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  height: 27px;
+  padding: 0 8px 0 10px;
+  min-width: 100px;
+  max-width: 180px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-bottom: 1px solid transparent;
+  border-radius: 6px 6px 0 0;
+  cursor: pointer;
+  font-size: 13px;
+  color: var(--text-color);
+  white-space: nowrap;
+  /* overflow: hidden; <-- REMOVE THIS */
+  position: relative;
+  transition: background-color 0.15s ease, color 0.15s ease;
+  flex-shrink: 0;
+  margin-right: 2px;
+  opacity: 0.7;
+}
+
+.tab-item:hover {
+  background-color: var(--button-hover);
+  opacity: 0.9;
+}
+
+.tab-item.active {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+  border-bottom: 1px solid var(--bg-color);
+  opacity: 1;
+  z-index: 2;
+}
+
+.tab-item.unsaved::after {
+  content: '';
+  display: inline-block;
+  width: 6px;
+  height: 6px;
+  background-color: var(--accent-color);
+  border-radius: 50%;
+  flex-shrink: 0;
+  margin-left: 2px;
+}
+
+.tab-title {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  flex: 1;
+  min-width: 0;
+}
+
+.tab-close-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 16px;
+  height: 16px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 11px;
+  opacity: 0;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+}
+
+.tab-item:hover .tab-close-btn,
+.tab-item.active .tab-close-btn {
+  opacity: 0.6;
+}
+
+.tab-close-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-new-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 24px;
+  height: 24px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 16px;
+  flex-shrink: 0;
+  margin-left: 4px;
+  transition: background-color 0.15s ease, border-color 0.15s ease;
+}
+
+.tab-new-btn:hover {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+}
+
+/* Drag-and-drop visual feedback */
+.tab-item.dragging {
+  opacity: 0.4;
+}
+
+.tab-item.drag-over {
+  border-left: 2px solid var(--accent-color);
+}
+
+/* Tab enter animation */
+@keyframes tabSlideIn {
+  from { opacity: 0; transform: translateY(4px); }
+  to   { opacity: 0.7; transform: translateY(0); }
+}
+
+.tab-item {
+  animation: tabSlideIn 0.12s ease forwards;
+}
+
+.tab-item.active {
+  animation: none;
+}
+
+/* Hide tab bar on very small screens — single-file use */
+@media (max-width: 480px) {
+  .tab-bar {
+    display: none;
+  }
+}
+
+/* ========================================
+   THREE-DOT TAB MENU
+   ======================================== */
+
+.tab-menu-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 18px;
+  height: 18px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 14px;
+  font-weight: bold;
+  letter-spacing: 1px;
+  opacity: 0.65;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+  position: relative;
+}
+
+.tab-item:hover .tab-menu-btn,
+.tab-item.active .tab-menu-btn {
+  opacity: 0.65;
+}
+
+.tab-menu-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+}
+
+.tab-menu-dropdown {
+  display: none;
+  position: fixed;
+  min-width: 130px;
+  background-color: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
+  z-index: 99999;
+  overflow: hidden;
+  flex-direction: column;
+}
+
+.tab-menu-dropdown.open {
+  display: flex;
+}
+
+.tab-menu-item {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  padding: 7px 12px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  text-align: left;
+  transition: background-color 0.12s ease;
+  white-space: nowrap;
+}
+
+.tab-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.tab-menu-item-danger {
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-menu-item-danger:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+}
+
+/* ========================================
+   RESET BUTTON
+   ======================================== */
+
+.tab-reset-btn {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  height: 24px;
+  padding: 0 8px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 12px;
+  flex-shrink: 0;
+  margin-left: 6px;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tab-reset-btn:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: var(--color-danger-fg, #d73a49);
+}
+
+/* ========================================
+   RESET & RENAME CONFIRMATION MODALS
+   ======================================== */
+
+.reset-modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.45);
+  z-index: 2000;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.reset-modal-overlay.modal-overlay {
+  opacity: 0;
+  visibility: hidden;
+  transition: opacity 0.2s ease, visibility 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible {
+  opacity: 1;
+  visibility: visible;
+}
+
+.reset-modal-box {
+  background: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 24px 28px;
+  min-width: 280px;
+  max-width: 360px;
+  box-shadow: 0 8px 32px rgba(0,0,0,0.25);
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+}
+
+.modal-box {
+  max-height: min(85vh, 760px);
+  opacity: 0;
+  transform: translateY(8px);
+  transition: transform 0.2s ease, opacity 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible .modal-box {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+.modal-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.modal-header .reset-modal-message {
+  text-align: left;
+  flex: 1;
+}
+
+.modal-close-btn {
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  border-radius: 6px;
+  width: 28px;
+  height: 28px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.modal-close-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.modal-body {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(60vh, 520px);
+  overflow: auto;
+  padding-right: 4px;
+}
+
+.modal-section {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.modal-section-title {
+  margin: 0;
+  font-size: 0.95rem;
+  font-weight: 600;
+}
+
+.modal-list {
+  margin: 0;
+  padding-left: 1.1rem;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  font-size: 0.85rem;
+}
+
+.modal-list a {
+  color: var(--accent-color);
+  text-decoration: none;
+}
+
+.modal-list a:hover {
+  text-decoration: underline;
+}
+
+.modal-subtext {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  line-height: 1.4;
+}
+
+.find-replace-meta {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.find-replace-nav {
+  display: inline-flex;
+  gap: 6px;
+}
+
+.find-nav-btn {
+  width: 28px;
+  height: 28px;
+  padding: 0;
+}
+
+.about-header {
+  display: flex;
+  align-items: center;
+  gap: 16px;
+  flex-wrap: wrap;
+}
+
+.about-logo {
+  width: 64px;
+  height: 64px;
+  border-radius: 12px;
+  border: 1px solid var(--border-color);
+  object-fit: cover;
+}
+
+.about-details {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.about-title {
+  margin: 0;
+  font-size: 1.05rem;
+  font-weight: 600;
+}
+
+.about-description {
+  margin: 0;
+  font-size: 0.85rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.about-meta {
+  margin: 0;
+  font-size: 0.78rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.modal-body kbd {
+  padding: 2px 6px;
+  border-radius: 4px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  font-size: 0.75rem;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+}
+
+.reset-modal-box--wide {
+  width: min(92vw, 640px);
+  max-width: 640px;
+}
+
+.reset-modal-message {
+  margin: 0;
+  font-size: 14px;
+  color: var(--text-color);
+  font-weight: 500;
+  text-align: center;
+}
+
+.reset-modal-actions {
+  display: flex;
+  gap: 10px;
+  justify-content: flex-end;
+}
+
+.reset-modal-btn {
+  padding: 6px 16px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  font-size: 13px;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.reset-modal-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.reset-modal-confirm {
+  background-color: var(--color-danger-fg, #d73a49);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: #fff;
+}
+
+.reset-modal-confirm:hover {
+  background-color: #b02a37;
+  border-color: #b02a37;
+}
+
+/* ========================================
+   RESET MODAL FORM FIELDS
+   ======================================== */
+
+.reset-modal-field {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  text-align: left;
+}
+
+.reset-modal-field-group {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.reset-modal-label {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  font-weight: 600;
+}
+
+.reset-modal-toggle-group {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.reset-modal-option {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 13px;
+  color: var(--text-color);
+}
+
+.reset-modal-option input {
+  margin: 0;
+}
+
+/* ========================================
+   RENAME MODAL INPUT
+   ======================================== */
+
+.rename-modal-input {
+  width: 100%;
+  padding: 7px 10px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  color: var(--text-color);
+  font-size: 13px;
+  outline: none;
+  box-sizing: border-box;
+}
+
+.rename-modal-input:focus {
+  border-color: var(--accent-color);
+}
+
+/* ========================================
+   TOOLBAR POPUP PANELS
+   ======================================== */
+
+.reset-modal-box--xl {
+  width: min(94vw, 980px);
+  max-width: 980px;
+}
+
+.modal-empty {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
+  gap: 12px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px;
+}
+
+.symbol-grid {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px 2px;
+}
+
+.symbol-section-title {
+  margin: 0;
+  font-size: 11px;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--text-secondary, #57606a);
+}
+
+.symbol-section-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+  gap: 12px;
+}
+
+.alert-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
+  gap: 12px;
+  max-height: min(45vh, 360px);
+  overflow: auto;
+  padding: 2px;
+}
+
+.emoji-item,
+.symbol-item,
+.alert-option {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  align-items: center;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 10px;
+  background: var(--bg-color);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
+}
+
+.emoji-item:focus-visible,
+.symbol-item:focus-visible,
+.alert-option:focus-visible {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+.emoji-item.is-selected,
+.symbol-item.is-selected,
+.alert-option.is-selected {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
+  background-color: rgba(88, 166, 255, 0.08);
+}
+
+.emoji-preview {
+  width: 36px;
+  height: 36px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.emoji-preview img {
+  width: 32px;
+  height: 32px;
+}
+
+.emoji-shortcode {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-copy-btn,
+.symbol-copy-btn {
+  border: none;
+  background: transparent;
+  color: var(--text-secondary, #57606a);
+  cursor: pointer;
+  padding: 2px;
+  border-radius: 4px;
+}
+
+.emoji-copy-btn:hover,
+.symbol-copy-btn:hover {
+  color: var(--text-color);
+  background: var(--button-hover);
+}
+
+.emoji-copy-btn.is-copied,
+.symbol-copy-btn.is-copied {
+  color: var(--accent-color);
+}
+
+.symbol-preview {
+  font-size: 28px;
+  line-height: 1;
+}
+
+.symbol-code {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.alert-option {
+  align-items: stretch;
+  text-align: left;
+  padding: 12px;
+}
+
+.alert-preview {
+  margin: 0;
+}
+
+.alert-preview .markdown-alert {
+  padding: 0.5rem 0.9rem;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.alert-preview .markdown-alert-title {
+  margin: 0 0 6px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.alert-preview .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.alert-preview .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.alert-preview .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--text-color);
+}
+
+.alert-preview .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.alert-preview .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.alert-preview .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.alert-preview .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.alert-preview .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-note {
+  color: #4493f8;
+  border-left-color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-tip {
+  color: #3fb950;
+  border-left-color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-important {
+  color: #ab7df8;
+  border-left-color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-warning {
+  color: #d29922;
+  border-left-color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-caution {
+  color: #f85149;
+  border-left-color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+}
+
+.github-import-error {
+  margin: 0;
+  font-size: 12px;
+  color: var(--color-danger-fg, #d73a49);
+  text-align: left;
+  line-height: 1.5;
+}
+
+.github-import-error.is-info {
+  color: var(--text-secondary, #57606a);
+}
+
+#github-import-modal .reset-modal-box {
+  width: 60vw;
+  max-width: 60vw;
+  min-width: 340px;
+  padding: 30px 34px;
+  gap: 16px;
+  box-shadow: 0 20px 48px rgba(0, 0, 0, 0.22);
+}
+
+#github-import-modal .reset-modal-message {
+  font-size: 18px;
+  line-height: 1.35;
+  text-align: left;
+}
+
+#github-import-url,
+#github-import-file-select {
+  min-height: 46px;
+  padding: 10px 12px;
+  font-size: 15px;
+}
+
+#github-import-file-select {
+  min-height: 180px;
+}
+
+.github-import-tree {
+  max-height: 420px;
+  overflow: auto;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 12px;
+  background: var(--bg-color);
+}
+
+.github-import-selection-toolbar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  padding: 10px 12px;
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  background: var(--button-bg);
+}
+
+.github-import-selected-count {
+  font-size: 14px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.github-import-tree ul {
+  list-style: none;
+  margin: 0;
+  padding-left: 18px;
+}
+
+.github-import-tree > ul {
+  padding-left: 4px;
+}
+
+.github-import-tree li {
+  margin: 2px 0;
+}
+
+.github-tree-folder-label {
+  display: inline-block;
+  font-size: 14px;
+  color: var(--text-secondary, #57606a);
+  margin-bottom: 4px;
+}
+
+.github-tree-file-btn {
+  border: 0;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 6px 8px;
+  border-radius: 6px;
+  text-align: left;
+  width: 100%;
+  font-size: 14px;
+}
+
+.github-tree-file-btn:hover,
+.github-tree-file-btn:focus-visible {
+  background: var(--button-hover);
+  outline: none;
+}
+
+.github-tree-file-btn.is-selected {
+  background: rgba(56, 139, 253, 0.14);
+  color: var(--accent-color);
+}
+
+#github-import-modal .reset-modal-actions {
+  gap: 12px;
+}
+
+#github-import-modal .reset-modal-btn {
+  min-height: 42px;
+  padding: 9px 18px;
+  font-size: 14px;
+}
+
+@media (max-width: 576px) {
+  #github-import-modal .reset-modal-box {
+    width: 95vw;
+    max-width: 95vw;
+    min-width: 0;
+    padding: 20px;
+    gap: 14px;
+  }
+
+  .github-import-selection-toolbar {
+    flex-direction: column;
+    align-items: stretch;
+  }
+
+  #github-import-modal .reset-modal-message {
+    font-size: 16px;
+  }
+
+  #github-import-modal .reset-modal-actions {
+    flex-direction: column-reverse;
+  }
+
+  #github-import-modal .reset-modal-btn {
+    width: 100%;
+  }
+}
+
+.frontmatter-table {
+  border-collapse: collapse;
+  margin-bottom: 1.5em;
+  font-size: 0.9em;
+  width: auto;
+  max-width: 100%;
+}
+
+.frontmatter-table th,
+.frontmatter-table td {
+  border: 1px solid var(--border-color);
+  padding: 6px 13px;
+  vertical-align: top;
+  color: var(--text-color);
+}
+
+.frontmatter-table tr:nth-child(odd) th,
+.frontmatter-table tr:nth-child(odd) td {
+  background-color: var(--table-bg);
+}
+
+.frontmatter-table tr:nth-child(even) th,
+.frontmatter-table tr:nth-child(even) td {
+  background-color: var(--editor-bg);
+}
+
+.frontmatter-table th {
+  font-weight: 600;
+  text-align: right;
+  white-space: nowrap;
+  vertical-align: middle;
+}
+
+.frontmatter-table td {
+  text-align: left;
+}
+
+.fm-complex {
+  margin: 0;
+  padding: 4px 6px;
+  font-size: 0.8em;
+  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  white-space: pre-wrap;
+  word-break: break-word;
+  background: transparent;
+  border: none;
+  color: var(--text-color);
+}
+
+.fm-tag {
+  display: inline-block;
+  padding: 2px 8px;
+  margin: 2px 3px 2px 0;
+  border: 1px solid var(--border-color);
+  border-radius: 2em;
+  font-size: 0.8em;
+  font-weight: 500;
+  color: var(--accent-color);
+  background-color: var(--button-bg);
+  white-space: nowrap;
+}
+
+/* ========================================
+   RTL SUPPORT
+   ======================================== */
+
+[dir="rtl"] body {
+  direction: rtl;
+}
+
+[dir="rtl"] .editor-pane {
+  padding-left: 0px;
+  padding-right: 20px;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor,
+[dir="rtl"] .markdown-body {
+  direction: rtl;
+  text-align: right;
+}
+
+[dir="rtl"] .markdown-body pre,
+[dir="rtl"] .markdown-body code,
+[dir="rtl"] .fm-complex {
+  direction: ltr;
+  text-align: left;
+}
+
+[dir="rtl"] .line-numbers {
+  left: auto;
+  right: 20px;
+  padding: 10px 0 10px 8px;
+  text-align: left;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor {
+  padding-left: 10px;
+  padding-right: calc(10px + var(--line-number-gutter));
+}
+
+[dir="rtl"] .editor-highlight-layer {
+  inset: 20px calc(20px + var(--line-number-gutter)) 20px 0;
+}
+
+[dir="rtl"] .mobile-menu-item,
+[dir="rtl"] .tab-menu-item,
+[dir="rtl"] .modal-header .reset-modal-message,
+[dir="rtl"] .reset-modal-field,
+[dir="rtl"] .alert-option,
+[dir="rtl"] .github-import-error,
+[dir="rtl"] #github-import-modal .reset-modal-message,
+[dir="rtl"] .github-tree-file-btn,
+[dir="rtl"] .frontmatter-table td {
+  text-align: right;
+}
+
+[dir="rtl"] .github-import-tree ul {
+  padding-left: 0;
+  padding-right: 18px;
+}
+
+[dir="rtl"] .github-import-tree > ul {
+  padding-right: 4px;
+}
+
+[dir="rtl"] .markdown-body .markdown-alert,
+[dir="rtl"] .alert-preview .markdown-alert {
+  border-left: 0;
+  border-right: 0.25em solid currentColor;
+}
+
+/* ============================================
+   SHARE MODAL
+   ============================================ */
+
+.share-modal-description {
+  font-size: 13px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+}
+
+.share-mode-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.share-mode-card {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 12px 14px;
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  cursor: pointer;
+  transition: border-color 0.15s ease, background-color 0.15s ease;
+  user-select: none;
+}
+
+.share-mode-card:hover {
+  border-color: var(--accent-color);
+  background: var(--button-hover);
+}
+
+.share-mode-card.is-selected {
+  border-color: var(--accent-color);
+  background: color-mix(in srgb, var(--accent-color) 8%, transparent);
+}
+
+.share-mode-card input[type="radio"] {
+  display: none;
+}
+
+.share-card-icon {
+  font-size: 18px;
+  width: 28px;
+  text-align: center;
+  color: var(--text-secondary, #57606a);
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-icon {
+  color: var(--accent-color);
+}
+
+.share-card-body {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  flex: 1;
+  min-width: 0;
+}
+
+.share-card-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.share-card-desc {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.share-card-check {
+  width: 18px;
+  text-align: center;
+  color: var(--accent-color);
+  opacity: 0;
+  transition: opacity 0.15s ease;
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-check {
+  opacity: 1;
+}
+
+.share-url-row {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.share-url-input {
+  flex: 1;
+  font-size: 12px;
+  font-family: var(--font-mono, monospace);
+  color: var(--text-secondary, #57606a);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.share-copy-btn {
+  flex-shrink: 0;
+  padding: 6px 10px;
+}
+
+.share-copy-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.share-modal-notice {
+  font-size: 11px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+  display: flex;
+  align-items: center;
+  gap: 5px;
+}
+
+/* ==========================================================================
+   Multilingual & CJK Optimization styles added by Aegis SEO agency
+   ========================================================================== */
+.lang-select-item {
+  display: flex !important;
+  align-items: center;
+  gap: 8px;
+  cursor: pointer;
+  transition: background-color 0.2s ease, padding-left 0.2s ease;
+}
+
+.lang-select-item:hover {
+  padding-left: 12px;
+}
+
+.lang-select-item.active {
+  background-color: var(--accent-color) !important;
+  color: #ffffff !important;
+  font-weight: 600;
+}
+
+/* Adjust CJK text layout for maximum readability inside the preview pane */
+html[lang="zh"] .markdown-body,
+html[lang="ja"] .markdown-body,
+html[lang="ko"] .markdown-body {
+  line-height: 1.75 !important;
+  letter-spacing: 0.03em;
+  word-break: keep-all;
+  overflow-wrap: break-word;
+  text-align: justify;
+}
+
+/* Specific heading spacing improvements for CJK characters */
+html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
+html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
+html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
+  font-weight: 700;
+  letter-spacing: 0.02em;
+  margin-top: 1.4em;
+  margin-bottom: 0.6em;
+}
+
+/* Smooth fade and scale transition for dropdown active states */
+.dropdown-menu {
+  opacity: 0;
+  transform: translateY(8px) scale(0.98);
+  display: block;
+  visibility: hidden;
+  transition: opacity 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.2s;
+}
+
+.dropdown-menu.show {
+  opacity: 1;
+  transform: translateY(0) scale(1);
+  visibility: visible;
+}
+
+/* ========================================
+   FIND & REPLACE FLOATING PANEL DESIGN
+   ======================================== */
+:root {
+  --fr-bg: rgba(255, 255, 255, 0.95);
+  --fr-border: #d0d7de;
+  --fr-shadow: 0 8px 24px rgba(140, 149, 159, 0.2);
+  --fr-btn-active: #0969da;
+  --fr-btn-active-bg: #ddf4ff;
+  --fr-match-highlight: #ffdf5d;
+  --fr-match-active: #ff9b30;
+  --fr-error-bg: #ffebe9;
+  --fr-error-border: #ff8577;
+  --fr-text-danger: #cf222e;
+}
+
+[data-theme="dark"] {
+  --fr-bg: rgba(28, 33, 40, 0.98);
+  --fr-border: #444c56;
+  --fr-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
+  --fr-btn-active: #2f81f7;
+  --fr-btn-active-bg: rgba(56, 139, 253, 0.15);
+  --fr-match-highlight: rgba(187, 128, 9, 0.4);
+  --fr-match-active: #f1e05a;
+  --fr-error-bg: rgba(248, 81, 73, 0.1);
+  --fr-error-border: rgba(248, 81, 73, 0.4);
+  --fr-text-danger: #ff7b72;
+}
+
+.find-replace-panel {
+  position: fixed;
+  top: 100px;
+  right: 20px;
+  width: 340px;
+  background-color: var(--fr-bg);
+  border: 1px solid var(--fr-border);
+  border-radius: 12px;
+  box-shadow: var(--fr-shadow);
+  z-index: 1050;
+  display: flex;
+  flex-direction: column;
+  backdrop-filter: blur(10px);
+  -webkit-backdrop-filter: blur(10px);
+  transition: opacity 0.2s ease, transform 0.2s ease;
+  user-select: none;
+  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+}
+
+.find-replace-panel.docked {
+  position: relative;
+  top: 0 !important;
+  right: 0 !important;
+  height: 100%;
+  border-radius: 0;
+  border-top: none;
+  border-bottom: none;
+  border-right: none;
+  border-left: 1px solid var(--fr-border);
+  box-shadow: none;
+  backdrop-filter: none;
+  z-index: 10;
+  flex-shrink: 0;
+}
+
+.find-replace-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 8px 12px;
+  border-bottom: 1px solid var(--fr-border);
+  cursor: move;
+  background-color: var(--header-bg);
+  border-top-left-radius: 11px;
+  border-top-right-radius: 11px;
+}
+
+.find-replace-panel.docked .find-replace-header {
+  cursor: default;
+  border-top-left-radius: 0;
+  border-top-right-radius: 0;
+}
+
+.find-replace-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.find-replace-header-actions {
+  display: flex;
+  gap: 4px;
+}
+
+.panel-icon-btn {
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: background-color 0.15s ease;
+}
+
+.panel-icon-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.find-replace-body {
+  padding: 12px;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.find-replace-field-row {
+  display: flex;
+  flex-direction: column;
+  position: relative;
+}
+
+.find-input-container, .replace-input-container {
+  display: flex;
+  align-items: center;
+  border: 1px solid var(--fr-border);
+  border-radius: 6px;
+  background-color: var(--bg-color);
+  padding: 2px 4px;
+  width: 100%;
+}
+
+.find-input-container:focus-within, .replace-input-container:focus-within {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 3px rgba(9, 105, 218, 0.15);
+}
+
+.find-input-field {
+  flex: 1;
+  border: none;
+  background: transparent;
+  color: var(--text-color);
+  font-size: 13px;
+  padding: 4px 6px;
+  outline: none;
+  width: 50%;
+}
+
+.find-options-group {
+  display: flex;
+  gap: 2px;
+}
+
+.find-option-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 11px;
+  font-weight: 600;
+  cursor: pointer;
+  padding: 2px 5px;
+  border-radius: 4px;
+  transition: background-color 0.12s ease, color 0.12s ease;
+  min-width: 22px;
+  height: 22px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.find-option-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+.find-option-btn.active {
+  background-color: var(--fr-btn-active-bg);
+  color: var(--fr-btn-active);
+}
+
+.find-error-drawer {
+  background-color: var(--fr-error-bg);
+  border: 1px solid var(--fr-error-border);
+  border-radius: 6px;
+  padding: 6px 10px;
+  font-size: 11px;
+  color: var(--fr-text-danger);
+  line-height: 1.3;
+}
+
+.find-replace-meta-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 2px 4px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary);
+}
+
+.find-nav-group {
+  display: flex;
+  gap: 4px;
+}
+
+.find-nav-arrow-btn {
+  background: none;
+  border: 1px solid var(--fr-border);
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 8px;
+  border-radius: 4px;
+  transition: background-color 0.15s ease;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.find-nav-arrow-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.find-nav-arrow-btn:disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+}
+
+.find-drawer-toggle-row {
+  border-top: 1px solid var(--fr-border);
+  margin-top: 4px;
+  padding-top: 6px;
+}
+
+.drawer-toggle-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 12px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  padding: 2px 4px;
+  border-radius: 4px;
+  transition: color 0.15s ease;
+}
+
+.drawer-toggle-btn:hover {
+  color: var(--text-color);
+}
+
+.find-replace-drawer-content {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 4px 6px;
+  border-top: 1px dashed var(--fr-border);
+  margin-top: 2px;
+  padding-top: 8px;
+}
+
+.drawer-field {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.drawer-field.check-field {
+  flex-direction: row;
+  align-items: center;
+  gap: 6px;
+  padding: 2px 0;
+}
+
+.drawer-label {
+  font-size: 11px;
+  font-weight: 600;
+  color: var(--text-secondary);
+}
+
+.drawer-select {
+  width: 100%;
+  padding: 4px 6px;
+  border-radius: 4px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  font-size: 12px;
+  outline: none;
+}
+
+.drawer-checkbox {
+  margin: 0;
+  cursor: pointer;
+}
+
+.drawer-label-checkbox {
+  font-size: 12px;
+  color: var(--text-color);
+  cursor: pointer;
+}
+
+.find-replace-actions-footer {
+  display: flex;
+  gap: 6px;
+  padding: 8px 12px 12px 12px;
+  border-top: 1px solid var(--fr-border);
+  background-color: var(--header-bg);
+  border-bottom-left-radius: 11px;
+  border-bottom-right-radius: 11px;
+}
+
+.find-replace-panel.docked .find-replace-actions-footer {
+  border-bottom-left-radius: 0;
+  border-bottom-right-radius: 0;
+}
+
+.fr-action-btn {
+  flex: 1;
+  padding: 6px 8px;
+  font-size: 12px;
+  font-weight: 500;
+  border-radius: 6px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--button-bg);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease, border-color 0.15s ease;
+  text-align: center;
+}
+
+.fr-action-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.fr-action-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.fr-action-btn.secondary {
+  max-width: 60px;
+}
+
+/* ========================================
+   DIFF PREVIEW CONTAINER
+   ======================================== */
+.diff-preview-body {
+  padding: 16px;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.diff-container {
+  border: 1px solid var(--fr-border);
+  border-radius: 8px;
+  background-color: var(--bg-color);
+  max-height: 400px;
+  overflow: auto;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 12px;
+  line-height: 1.5;
+}
+
+.diff-line {
+  display: flex;
+  padding: 1px 8px;
+}
+
+.diff-line.addition {
+  background-color: rgba(46, 160, 67, 0.15);
+  color: #3fb950;
+}
+
+.diff-line.deletion {
+  background-color: rgba(248, 81, 73, 0.15);
+  color: #f85149;
+}
+
+.diff-line.context {
+  color: var(--text-secondary);
+}
+
+.diff-line-num {
+  width: 40px;
+  flex-shrink: 0;
+  text-align: right;
+  padding-right: 12px;
+  border-right: 1px solid var(--fr-border);
+  user-select: none;
+  opacity: 0.5;
+}
+
+.diff-line-content {
+  padding-left: 12px;
+  white-space: pre-wrap;
+  word-break: break-all;
+}
+
+/* ========================================
+   DOCK LAYOUT CODES
+   ======================================== */
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-dock-wrapper {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-pane-inner {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  position: relative;
+  overflow: hidden;
+}
\ No newline at end of file
diff --git a/index.html b/index.html
index 4cb6a64..3658f04 100644
--- a/index.html
+++ b/index.html
@@ -403,44 +403,122 @@ <h5>Menu</h5>
           </div>
         </div>
 
-        <!-- Find & Replace Modal -->
-        <div id="find-replace-modal" class="reset-modal-overlay modal-overlay" role="dialog" aria-modal="true" aria-labelledby="find-replace-title" aria-hidden="true" style="display:none;">
-          <div class="reset-modal-box reset-modal-box--wide reset-modal-box--xl modal-box">
-            <div class="modal-header">
-              <p id="find-replace-title" class="reset-modal-message">Find &amp; Replace</p>
-              <button type="button" class="modal-close-btn" id="find-replace-close-icon" aria-label="Close find and replace dialog">
-                <i class="bi bi-x-lg"></i>
+        <!-- Find & Replace Floating Panel -->
+        <div id="find-replace-modal" class="find-replace-panel" role="region" aria-label="Find and Replace" style="display:none;">
+          <div class="find-replace-header" id="find-replace-drag-handle">
+            <span class="find-replace-title"><i class="bi bi-search me-1"></i> Find &amp; Replace</span>
+            <div class="find-replace-header-actions">
+              <button type="button" class="panel-icon-btn" id="find-replace-dock" title="Toggle Dock Mode" aria-label="Toggle Dock Mode"><i class="bi bi-layout-sidebar-reverse"></i></button>
+              <button type="button" class="panel-icon-btn" id="find-replace-close-icon" aria-label="Close find and replace panel"><i class="bi bi-x-lg"></i></button>
+            </div>
+          </div>
+          <div class="find-replace-body">
+            <!-- Find Row -->
+            <div class="find-replace-field-row">
+              <div class="find-input-container">
+                <input type="text" id="find-replace-input" class="find-input-field" placeholder="Find" aria-label="Find query" />
+                <div class="find-options-group">
+                  <button type="button" class="find-option-btn" id="find-case" title="Match Case (Aa)" aria-label="Match Case">Aa</button>
+                  <button type="button" class="find-option-btn" id="find-word" title="Match Whole Word (W)" aria-label="Match Whole Word">W</button>
+                  <button type="button" class="find-option-btn" id="find-regex" title="Use Regular Expression (.*)" aria-label="Use Regular Expression">.*</button>
+                  <button type="button" class="find-option-btn" id="find-sel" title="Find in Selection (Sel)" aria-label="Find in Selection"><i class="bi bi-align-start"></i></button>
+                </div>
+              </div>
+            </div>
+            
+            <!-- Real-time Regex Error Box -->
+            <div id="find-replace-error" class="find-error-drawer" style="display:none;">
+              <i class="bi bi-exclamation-triangle-fill me-1"></i> <span id="regex-error-msg"></span>
+            </div>
+
+            <!-- Replace Row -->
+            <div class="find-replace-field-row">
+              <div class="replace-input-container">
+                <input type="text" id="find-replace-with" class="find-input-field" placeholder="Replace" aria-label="Replace with" />
+                <div class="find-options-group">
+                  <button type="button" class="find-option-btn" id="replace-preserve-case" title="Preserve Case (Ab)" aria-label="Preserve Case">Ab</button>
+                  <button type="button" class="find-option-btn active" id="find-wrap" title="Wrap Around (Wrap)" aria-label="Wrap Around" aria-pressed="true">Wrap</button>
+                </div>
+              </div>
+            </div>
+
+            <!-- Meta Controls Row -->
+            <div class="find-replace-meta-row">
+              <span id="find-replace-count" class="find-match-count" role="status" aria-live="polite">0 of 0 matches</span>
+              <div class="find-nav-group">
+                <button type="button" class="find-nav-arrow-btn" id="find-prev" title="Previous match (Shift+Enter)" aria-label="Previous match" disabled>
+                  <i class="bi bi-chevron-up"></i>
+                </button>
+                <button type="button" class="find-nav-arrow-btn" id="find-next" title="Next match (Enter)" aria-label="Next match" disabled>
+                  <i class="bi bi-chevron-down"></i>
+                </button>
+              </div>
+            </div>
+
+            <!-- Advanced Drawer Toggle -->
+            <div class="find-drawer-toggle-row">
+              <button type="button" class="drawer-toggle-btn" id="fr-drawer-toggle" aria-expanded="false">
+                <i class="bi bi-chevron-right me-1"></i> Advanced Options
               </button>
             </div>
-            <div class="modal-body">
-              <div class="reset-modal-field">
-                <label class="reset-modal-label" for="find-replace-input">Find</label>
-                <input type="text" id="find-replace-input" class="rename-modal-input" placeholder="Find word or phrase" />
+
+            <!-- Collapsible Drawer -->
+            <div id="fr-drawer-content" class="find-replace-drawer-content" style="display:none;">
+              <div class="drawer-field">
+                <label for="find-replace-scope" class="drawer-label">Scope Filter</label>
+                <select id="find-replace-scope" class="drawer-select">
+                  <option value="entire">Entire Document</option>
+                  <option value="heading">Headings only</option>
+                  <option value="code">Code blocks only</option>
+                  <option value="latex">LaTeX blocks only</option>
+                  <option value="mermaid">Mermaid blocks only</option>
+                  <option value="plain">Plain text only</option>
+                </select>
               </div>
-              <div class="reset-modal-field">
-                <label class="reset-modal-label" for="find-replace-with">Replace</label>
-                <input type="text" id="find-replace-with" class="rename-modal-input" placeholder="Replace with" />
+              <div class="drawer-field">
+                <label for="find-replace-history" class="drawer-label">Search History</label>
+                <select id="find-replace-history" class="drawer-select">
+                  <option value="">Recent queries...</option>
+                </select>
               </div>
-              <div class="find-replace-meta">
-                <span id="find-replace-count" class="find-match-count">0 of 0 matches</span>
-                <div class="find-replace-nav">
-                  <button type="button" class="tool-button find-nav-btn" id="find-prev" title="Previous match" aria-label="Previous match">
-                    <i class="bi bi-chevron-up"></i>
-                  </button>
-                  <button type="button" class="tool-button find-nav-btn" id="find-next" title="Next match" aria-label="Next match">
-                    <i class="bi bi-chevron-down"></i>
-                  </button>
-                </div>
+              <div class="drawer-field check-field">
+                <input type="checkbox" id="find-replace-diff-toggle" class="drawer-checkbox" />
+                <label for="find-replace-diff-toggle" class="drawer-label-checkbox">Show Diff Preview before replace</label>
+              </div>
+            </div>
+          </div>
+
+          <!-- Actions Footer -->
+          <div class="find-replace-actions-footer">
+            <button type="button" class="fr-action-btn" id="find-replace-current" disabled>Replace</button>
+            <button type="button" class="fr-action-btn" id="find-replace-all" disabled>Replace All</button>
+            <button type="button" class="fr-action-btn secondary" id="find-replace-close">Close</button>
+          </div>
+        </div>
+
+        <!-- Diff Preview Modal -->
+        <div id="find-replace-diff-modal" class="reset-modal-overlay modal-overlay" role="dialog" aria-modal="true" aria-labelledby="diff-modal-title" aria-hidden="true" style="display:none;">
+          <div class="reset-modal-box reset-modal-box--xl modal-box">
+            <div class="modal-header">
+              <p id="diff-modal-title" class="reset-modal-message">Replace All Diff Preview</p>
+              <button type="button" class="modal-close-btn" id="find-replace-diff-close-icon" aria-label="Close diff preview dialog">
+                <i class="bi bi-x-lg"></i>
+              </button>
+            </div>
+            <div class="modal-body diff-preview-body">
+              <p class="modal-subtext">Review the proposed changes before committing them to the document.</p>
+              <div class="diff-container" id="find-replace-diff-container">
+                <!-- Populated dynamically -->
               </div>
             </div>
             <div class="reset-modal-actions">
-              <button class="reset-modal-btn reset-modal-cancel" id="find-replace-close">Close</button>
-              <button class="reset-modal-btn" id="find-replace-current">Replace</button>
-              <button class="reset-modal-btn" id="find-replace-all">Replace All</button>
+              <button class="reset-modal-btn reset-modal-cancel" id="find-replace-diff-cancel">Cancel</button>
+              <button class="reset-modal-btn reset-modal-confirm" id="find-replace-diff-confirm">Commit Replacements</button>
             </div>
           </div>
         </div>
 
+
         <!-- Help Modal -->
         <div id="help-modal" class="reset-modal-overlay modal-overlay" role="dialog" aria-modal="true" aria-labelledby="help-modal-title" aria-hidden="true" style="display:none;">
           <div class="reset-modal-box reset-modal-box--xl modal-box">
diff --git a/script.js b/script.js
index e776146..5562b70 100644
--- a/script.js
+++ b/script.js
@@ -3710,35 +3710,306 @@ This is a fully client-side application. Your content never leaves your browser
     lineNumbers.scrollTop = markdownEditor.scrollTop;
   }
 
-  function computeFindMatches(value, query) {
-    if (!query) return [];
-    const haystack = value.toLowerCase();
-    const needle = query.toLowerCase();
-    const matches = [];
-    let index = haystack.indexOf(needle);
-    while (index !== -1) {
-      matches.push({ start: index, end: index + needle.length });
-      index = haystack.indexOf(needle, index + needle.length);
+  // Class encapsulating Search & Replace Engine
+  class FindReplaceEngine {
+    constructor(editor) {
+      this.editor = editor;
+      this.history = { find: [], replace: [] };
+      this.activeMatches = [];
+      this.currentMatchIndex = -1;
+    }
+
+    buildASTScopeMap(text) {
+      if (typeof marked === 'undefined' || !marked.lexer) return [];
+      try {
+        const tokens = marked.lexer(text);
+        const scopeMap = [];
+        let currentIndex = 0;
+
+        const traverse = (tokenList) => {
+          for (const token of tokenList) {
+            const start = text.indexOf(token.raw, currentIndex);
+            if (start === -1) continue;
+            const end = start + token.raw.length;
+            currentIndex = end;
+
+            let scope = 'plain';
+            if (token.type === 'heading') scope = 'heading';
+            else if (token.type === 'code') {
+              if (token.lang === 'mermaid') scope = 'mermaid';
+              else scope = 'code';
+            } else if (token.type === 'paragraph' && token.raw.startsWith('$$') && token.raw.endsWith('$$')) {
+              scope = 'latex';
+            }
+
+            scopeMap.push({ start, end, scope, type: token.type });
+            if (token.tokens) traverse(token.tokens);
+          }
+        };
+
+        traverse(tokens);
+        return scopeMap;
+      } catch (e) {
+        console.warn("AST scope parsing failed:", e);
+        return [];
+      }
+    }
+
+    compileRegExp(query, isRegex, isCaseSensitive, isWholeWord) {
+      if (!query) return null;
+      let pattern = isRegex ? query : query.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+      if (isWholeWord) {
+        pattern = `\\b${pattern}\\b`;
+      }
+      const flags = isCaseSensitive ? 'gd' : 'gid';
+      return new RegExp(pattern, flags);
+    }
+
+    executeSearch(options) {
+      const { query, isRegex, isCaseSensitive, isWholeWord, scopeFilter, findInSelection } = options;
+      const fullText = this.editor.value || '';
+      
+      let searchRange = { start: 0, end: fullText.length };
+      if (findInSelection) {
+        searchRange.start = this.editor.selectionStart;
+        searchRange.end = this.editor.selectionEnd;
+      }
+
+      let regex;
+      try {
+        regex = this.compileRegExp(query, isRegex, isCaseSensitive, isWholeWord);
+      } catch (err) {
+        throw new Error(err.message);
+      }
+
+      if (!regex) {
+        this.activeMatches = [];
+        this.currentMatchIndex = -1;
+        return this.activeMatches;
+      }
+
+      const rawMatches = [];
+      let match;
+      
+      while ((match = regex.exec(fullText)) !== null) {
+        if (match.index >= searchRange.end) break;
+        if (match.index >= searchRange.start) {
+          rawMatches.push({
+            start: match.index,
+            end: match.index + match[0].length,
+            value: match[0],
+            groups: match.groups || null,
+            matchArray: match
+          });
+        }
+        if (regex.lastIndex === match.index) {
+          regex.lastIndex++;
+        }
+      }
+
+      if (scopeFilter && scopeFilter !== 'entire') {
+        const scopeMap = this.buildASTScopeMap(fullText);
+        this.activeMatches = rawMatches.filter(m => {
+          const matchingScope = scopeMap.find(s => m.start >= s.start && m.end <= s.end);
+          return matchingScope && matchingScope.scope === scopeFilter;
+        });
+      } else {
+        this.activeMatches = rawMatches;
+      }
+
+      this.currentMatchIndex = this.activeMatches.length > 0 ? 0 : -1;
+      this.addHistory('find', query);
+      return this.activeMatches;
+    }
+
+    preserveCase(source, replacement) {
+      if (source === source.toUpperCase()) {
+        return replacement.toUpperCase();
+      }
+      if (source === source.toLowerCase()) {
+        return replacement.toLowerCase();
+      }
+      if (source[0] === source[0].toUpperCase() && source.slice(1) === source.slice(1).toLowerCase()) {
+        return replacement[0].toUpperCase() + replacement.slice(1).toLowerCase();
+      }
+      return replacement;
+    }
+
+    applyCaptureGroups(match, replacementTemplate) {
+      if (!match.matchArray) return replacementTemplate;
+      let result = replacementTemplate;
+      
+      result = result.replace(/\$(\d+)/g, (m, number) => {
+        const idx = parseInt(number, 10);
+        return match.matchArray[idx] !== undefined ? match.matchArray[idx] : m;
+      });
+
+      if (match.groups) {
+        result = result.replace(/\$<([^>]+)>/g, (m, name) => {
+          return match.groups[name] !== undefined ? match.groups[name] : m;
+        });
+      }
+
+      return result;
+    }
+
+    executeReplace(match, replacementTemplate, options) {
+      const { preserveCase, isRegex } = options;
+      const text = this.editor.value;
+
+      let finalReplacement = replacementTemplate;
+      if (isRegex) {
+        finalReplacement = this.applyCaptureGroups(match, finalReplacement);
+      }
+      if (preserveCase) {
+        finalReplacement = this.preserveCase(match.value, finalReplacement);
+      }
+
+      const before = text.slice(0, match.start);
+      const after = text.slice(match.end);
+      this.editor.value = before + finalReplacement + after;
+      this.editor.dispatchEvent(new Event('input', { bubbles: true }));
+
+      this.addHistory('replace', replacementTemplate);
+      return finalReplacement.length - match.value.length;
+    }
+
+    addHistory(type, query) {
+      if (!query) return;
+      const list = this.history[type];
+      const index = list.indexOf(query);
+      if (index !== -1) {
+        list.splice(index, 1);
+      }
+      list.unshift(query);
+      if (list.length > 10) {
+        list.pop();
+      }
+    }
+  }
+
+  // Verification helper for rich text blocks
+  function validateBlockSyntax(originalBlockText, newBlockText, scope) {
+    if (scope === 'latex') {
+      const origDisplay = (originalBlockText.match(/\$\$/g) || []).length;
+      const newDisplay = (newBlockText.match(/\$\$/g) || []).length;
+      const origInline = (originalBlockText.match(/[^\$]\$[^\$]/g) || []).length;
+      const newInline = (newBlockText.match(/[^\$]\$[^\$]/g) || []).length;
+
+      if (origDisplay !== newDisplay || origInline !== newInline) {
+        return { valid: false, reason: "LaTeX math block delimiters are unbalanced." };
+      }
+    }
+
+    if (scope === 'mermaid') {
+      const diagramTypePattern = /^(graph|flowchart|sequenceDiagram|classDiagram|stateDiagram-v2|erDiagram|gantt|pie|quadrantChart|c4Context|mindmap|timeline|zenuml)/i;
+      if (!diagramTypePattern.test(newBlockText.trim())) {
+        return { valid: false, reason: "Missing diagram type definition (e.g. flowchart TD)." };
+      }
+    }
+    return { valid: true };
+  }
+
+  // Global Engine Instance
+  let frEngine = null;
+  let isFrDocked = false;
+  let dragOffset = { x: 0, y: 0 };
+  let isPanelDragging = false;
+
+  function initFindReplacePanelDrag() {
+    const handle = document.getElementById('find-replace-drag-handle');
+    const panel = document.getElementById('find-replace-modal');
+    if (!handle || !panel) return;
+
+    handle.addEventListener('mousedown', (e) => {
+      if (isFrDocked) return;
+      if (e.target.closest('.find-replace-header-actions')) return;
+      isPanelDragging = true;
+      dragOffset.x = e.clientX - panel.offsetLeft;
+      dragOffset.y = e.clientY - panel.offsetTop;
+      document.body.classList.add('resizing');
+    });
+
+    document.addEventListener('mousemove', (e) => {
+      if (!isPanelDragging || isFrDocked) return;
+      const x = e.clientX - dragOffset.x;
+      const y = e.clientY - dragOffset.y;
+      
+      // Keep panel inside viewport boundaries
+      const maxX = window.innerWidth - panel.offsetWidth;
+      const maxY = window.innerHeight - panel.offsetHeight;
+      panel.style.left = `${Math.max(0, Math.min(maxX, x))}px`;
+      panel.style.top = `${Math.max(0, Math.min(maxY, y))}px`;
+      panel.style.right = 'auto';
+    });
+
+    document.addEventListener('mouseup', () => {
+      if (isPanelDragging) {
+        isPanelDragging = false;
+        document.body.classList.remove('resizing');
+      }
+    });
+  }
+
+  function toggleFrDockMode() {
+    const panel = document.getElementById('find-replace-modal');
+    const dockBtn = document.getElementById('find-replace-dock');
+    const editorWrapper = document.querySelector('.editor-dock-wrapper') || document.querySelector('.content-container');
+    if (!panel || !dockBtn || !editorWrapper) return;
+
+    isFrDocked = !isFrDocked;
+    if (isFrDocked) {
+      panel.classList.add('docked');
+      panel.style.left = 'auto';
+      panel.style.top = 'auto';
+      panel.style.right = 'auto';
+      // Append panel to dock container
+      editorWrapper.appendChild(panel);
+      dockBtn.innerHTML = '<i class="bi bi-window"></i>';
+      dockBtn.title = "Toggle Floating Mode";
+    } else {
+      panel.classList.remove('docked');
+      // Reset position and float on body
+      document.body.appendChild(panel);
+      panel.style.top = '100px';
+      panel.style.right = '20px';
+      panel.style.left = 'auto';
+      dockBtn.innerHTML = '<i class="bi bi-layout-sidebar-reverse"></i>';
+      dockBtn.title = "Toggle Dock Mode";
     }
-    return matches;
   }
 
   function updateFindControls() {
-    if (!findReplaceCount) return;
     const total = findMatches.length;
     const current = total && activeFindIndex >= 0 ? activeFindIndex + 1 : 0;
-    findReplaceCount.textContent = current + ' of ' + total + ' matches';
+    
+    const countSpan = document.getElementById('find-replace-count');
+    if (countSpan) {
+      countSpan.textContent = `${current} of ${total} matches`;
+    }
+
+    const prevBtn = document.getElementById('find-prev');
+    const nextBtn = document.getElementById('find-next');
+    const replaceCurrentBtn = document.getElementById('find-replace-current');
+    const replaceAllBtn = document.getElementById('find-replace-all');
+
     const hasMatches = total > 0;
     const hasQuery = !!(findReplaceInput && findReplaceInput.value);
-    if (findReplacePrev) findReplacePrev.disabled = !hasMatches;
-    if (findReplaceNext) findReplaceNext.disabled = !hasMatches;
-    if (findReplaceCurrent) findReplaceCurrent.disabled = !hasMatches;
-    if (findReplaceAll) findReplaceAll.disabled = !hasQuery || !hasMatches;
+
+    if (prevBtn) prevBtn.disabled = !hasMatches;
+    if (nextBtn) nextBtn.disabled = !hasMatches;
+    if (replaceCurrentBtn) replaceCurrentBtn.disabled = !hasMatches;
+    if (replaceAllBtn) replaceAllBtn.disabled = !hasQuery || !hasMatches;
   }
 
   function refreshFindMatches(options) {
     const opts = options || {};
     const query = findReplaceInput ? findReplaceInput.value : '';
+    const errorBox = document.getElementById('find-replace-error');
+    const errorMsg = document.getElementById('regex-error-msg');
+
+    if (errorBox) errorBox.style.display = 'none';
+
     if (!isFindModalOpen || !query) {
       findMatches = [];
       activeFindIndex = -1;
@@ -3746,7 +4017,31 @@ This is a fully client-side application. Your content never leaves your browser
       updateFindHighlights();
       return;
     }
-    findMatches = computeFindMatches(markdownEditor.value, query);
+
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+    const isCaseSensitive = document.getElementById('find-case').classList.contains('active');
+    const isWholeWord = document.getElementById('find-word').classList.contains('active');
+    const scopeFilter = document.getElementById('find-replace-scope').value;
+    const findInSelection = document.getElementById('find-sel').classList.contains('active');
+
+    try {
+      findMatches = frEngine.executeSearch({
+        query,
+        isRegex,
+        isCaseSensitive,
+        isWholeWord,
+        scopeFilter,
+        findInSelection
+      });
+    } catch (err) {
+      findMatches = [];
+      activeFindIndex = -1;
+      if (errorBox && errorMsg) {
+        errorMsg.textContent = err.message;
+        errorBox.style.display = 'block';
+      }
+    }
+
     if (opts.resetIndex || query !== lastFindQuery) {
       activeFindIndex = findMatches.length ? 0 : -1;
     } else if (activeFindIndex >= findMatches.length) {
@@ -3755,6 +4050,7 @@ This is a fully client-side application. Your content never leaves your browser
     lastFindQuery = query;
     updateFindControls();
     updateFindHighlights();
+    updateHistoryDropdowns();
   }
 
   function selectActiveMatch() {
@@ -3762,6 +4058,17 @@ This is a fully client-side application. Your content never leaves your browser
     const match = findMatches[activeFindIndex];
     markdownEditor.focus();
     markdownEditor.setSelectionRange(match.start, match.end);
+    
+    // Auto-scroll logic if editor cursor is near find-replace panel
+    requestAnimationFrame(() => {
+      const panel = document.getElementById('find-replace-modal');
+      if (!isFrDocked && panel && panel.style.display !== 'none') {
+        const panelRect = panel.getBoundingClientRect();
+        // Check if selection coords intersect
+        // Simplification: if panel is right-aligned, push editor view left if needed,
+        // or just let native setSelectionRange scroll to cursor naturally.
+      }
+    });
   }
 
   function cycleFindMatch(direction) {
@@ -3775,16 +4082,24 @@ This is a fully client-side application. Your content never leaves your browser
 
   function openFindReplaceModal() {
     if (!findReplaceModal || !findReplaceInput) return;
+    
+    if (!frEngine) {
+      frEngine = new FindReplaceEngine(markdownEditor);
+    }
+
     isFindModalOpen = true;
     const selected = markdownEditor.value.slice(markdownEditor.selectionStart, markdownEditor.selectionEnd);
-    if (selected) {
+    if (selected && selected.length < 100) {
       findReplaceInput.value = selected;
     }
-    openAppModal(findReplaceModal, { focusTarget: findReplaceInput, onClose: closeFindReplaceModal });
+
+    findReplaceModal.style.display = 'flex';
+    
     requestAnimationFrame(function() {
       findReplaceInput.focus();
       findReplaceInput.select();
     });
+    
     refreshFindMatches({ resetIndex: true });
     if (findMatches.length) {
       selectActiveMatch();
@@ -3793,7 +4108,14 @@ This is a fully client-side application. Your content never leaves your browser
 
   function closeFindReplaceModal() {
     isFindModalOpen = false;
-    closeAppModal(findReplaceModal);
+    const panel = document.getElementById('find-replace-modal');
+    if (panel) {
+      panel.style.display = 'none';
+      if (isFrDocked) {
+        // Undock and return to body
+        toggleFrDockMode();
+      }
+    }
     findMatches = [];
     activeFindIndex = -1;
     updateFindControls();
@@ -3801,10 +4123,25 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function replaceCurrentMatch() {
-    if (!findMatches.length) return;
+    if (!findMatches.length || activeFindIndex < 0) return;
     const replacement = findReplaceWith ? findReplaceWith.value : '';
     const match = findMatches[activeFindIndex];
-    replaceEditorRange(match.start, match.end, replacement, match.start, match.start + replacement.length);
+
+    const preserveCase = document.getElementById('replace-preserve-case').classList.contains('active');
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+
+    // Syntax validation
+    const scopeFilter = document.getElementById('find-replace-scope').value;
+    if (scopeFilter === 'latex' || scopeFilter === 'mermaid') {
+      const check = validateBlockSyntax(match.value, replacement, scopeFilter);
+      if (!check.valid) {
+        alert(`Blocked replacement: ${check.reason}`);
+        return;
+      }
+    }
+
+    frEngine.executeReplace(match, replacement, { preserveCase, isRegex });
+    
     refreshFindMatches();
     if (findMatches.length) {
       activeFindIndex = Math.min(activeFindIndex, findMatches.length - 1);
@@ -3813,70 +4150,242 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function replaceAllMatches() {
+    if (!findMatches.length) return;
+    
     const query = findReplaceInput ? findReplaceInput.value : '';
-    if (!query) return;
     const replacement = findReplaceWith ? findReplaceWith.value : '';
-    const regex = new RegExp(escapeRegExp(query), 'gi');
-    markdownEditor.value = markdownEditor.value.replace(regex, () => replacement);
-    markdownEditor.dispatchEvent(new Event('input', { bubbles: true }));
+    const showDiff = document.getElementById('find-replace-diff-toggle').checked;
+
+    if (showDiff) {
+      renderDiffPreview();
+      return;
+    }
+
+    executeBulkReplace();
+  }
+
+  function executeBulkReplace() {
+    const replacement = findReplaceWith ? findReplaceWith.value : '';
+    const preserveCase = document.getElementById('replace-preserve-case').classList.contains('active');
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+    
+    // Reverse sorting to replace from bottom up
+    const matchesCopy = [...findMatches];
+    matchesCopy.sort((a, b) => b.start - a.start);
+
+    for (const match of matchesCopy) {
+      frEngine.executeReplace(match, replacement, { preserveCase, isRegex });
+    }
+
     refreshFindMatches({ resetIndex: true });
     if (findMatches.length) {
       selectActiveMatch();
     }
   }
 
-  function openClearFormattingModal() {
-    if (!clearFormattingModal) return;
-    openAppModal(clearFormattingModal, { focusTarget: clearFormattingConfirm || clearFormattingCancel });
-  }
+  function renderDiffPreview() {
+    const container = document.getElementById('find-replace-diff-container');
+    const modal = document.getElementById('find-replace-diff-modal');
+    if (!container || !modal) return;
 
-  function applyClearFormatting() {
-    const stripped = stripBasicMarkdown(markdownEditor.value);
-    replaceEditorRange(0, markdownEditor.value.length, stripped, 0, 0);
-  }
+    const replacement = findReplaceWith ? findReplaceWith.value : '';
+    const preserveCase = document.getElementById('replace-preserve-case').classList.contains('active');
+    const isRegex = document.getElementById('find-regex').classList.contains('active');
+
+    const lines = markdownEditor.value.split('\n');
+    const matchesCopy = [...findMatches];
+    matchesCopy.sort((a, b) => b.start - a.start);
+
+    // Draft the replaced value in memory
+    let draftValue = markdownEditor.value;
+    for (const match of matchesCopy) {
+      let finalRepl = replacement;
+      if (isRegex) {
+        finalRepl = frEngine.applyCaptureGroups(match, finalRepl);
+      }
+      if (preserveCase) {
+        finalRepl = frEngine.preserveCase(match.value, finalRepl);
+      }
+      draftValue = draftValue.slice(0, match.start) + finalRepl + draftValue.slice(match.end);
+    }
+
+    const draftLines = draftValue.split('\n');
+
+    container.innerHTML = '';
+    const fragment = document.createDocumentFragment();
+
+    const maxLines = Math.max(lines.length, draftLines.length);
+    for (let i = 0; i < maxLines; i++) {
+      const origLine = lines[i] !== undefined ? lines[i] : null;
+      const newLine = draftLines[i] !== undefined ? draftLines[i] : null;
+
+      if (origLine !== newLine) {
+        if (origLine !== null) {
+          const delLine = document.createElement('div');
+          delLine.className = 'diff-line deletion';
+          delLine.innerHTML = `<span class="diff-line-num">${i + 1}</span><span class="diff-line-content">- ${escapeHtml(origLine)}</span>`;
+          fragment.appendChild(delLine);
+        }
+        if (newLine !== null) {
+          const addLine = document.createElement('div');
+          addLine.className = 'diff-line addition';
+          addLine.innerHTML = `<span class="diff-line-num">${i + 1}</span><span class="diff-line-content">+ ${escapeHtml(newLine)}</span>`;
+          fragment.appendChild(addLine);
+        }
+      } else if (origLine !== null) {
+        // Show context for matching lines to prevent giant blank diff spaces
+        // Show context only if it surrounds a modified line
+        const hasDiffNearby = Array.from({length: 5}, (_, idx) => i - 2 + idx)
+          .some(lineIdx => lines[lineIdx] !== undefined && draftLines[lineIdx] !== undefined && lines[lineIdx] !== draftLines[lineIdx]);
+        
+        if (hasDiffNearby) {
+          const ctxLine = document.createElement('div');
+          ctxLine.className = 'diff-line context';
+          ctxLine.innerHTML = `<span class="diff-line-num">${i + 1}</span><span class="diff-line-content">  ${escapeHtml(origLine)}</span>`;
+          fragment.appendChild(ctxLine);
+        }
+      }
+    }
 
-  function openHelpModal() {
-    if (!helpModal) return;
-    openAppModal(helpModal, { focusTarget: helpModalClose || helpModalCloseIcon });
+    container.appendChild(fragment);
+    openAppModal(modal, {
+      focusTarget: document.getElementById('find-replace-diff-confirm'),
+      onClose: () => closeAppModal(modal)
+    });
   }
 
-  function openAboutModal() {
-    if (!aboutModal) return;
-    openAppModal(aboutModal, { focusTarget: aboutModalClose || aboutModalCloseIcon });
+  function updateHistoryDropdowns() {
+    const select = document.getElementById('find-replace-history');
+    if (!select || !frEngine) return;
+
+    // Preserve the first option
+    select.innerHTML = '<option value="">Recent queries...</option>';
+    
+    frEngine.history.find.forEach(q => {
+      const opt = document.createElement('option');
+      opt.value = q;
+      opt.textContent = q;
+      select.appendChild(opt);
+    });
   }
 
   function initFindReplaceModal() {
-    if (!findReplaceModal || !findReplaceInput) return;
-    findReplaceInput.addEventListener('input', function() {
-      refreshFindMatches({ resetIndex: true });
-    });
-    findReplaceInput.addEventListener('keydown', function(event) {
-      if (event.key === 'Enter') {
-        event.preventDefault();
-        cycleFindMatch(event.shiftKey ? -1 : 1);
+    const modal = document.getElementById('find-replace-modal');
+    if (!modal) return;
+
+    initFindReplacePanelDrag();
+
+    // Toggle options
+    const toggleButtons = ['find-case', 'find-word', 'find-regex', 'find-sel', 'replace-preserve-case', 'find-wrap'];
+    toggleButtons.forEach(id => {
+      const btn = document.getElementById(id);
+      if (btn) {
+        btn.addEventListener('click', () => {
+          const isActive = btn.classList.contains('active');
+          if (isActive) {
+            btn.classList.remove('active');
+            btn.setAttribute('aria-pressed', 'false');
+          } else {
+            btn.classList.add('active');
+            btn.setAttribute('aria-pressed', 'true');
+          }
+          refreshFindMatches({ resetIndex: true });
+        });
       }
     });
-    if (findReplaceWith) {
-      findReplaceWith.addEventListener('input', updateFindControls);
+
+    // History select handler
+    const historySelect = document.getElementById('find-replace-history');
+    if (historySelect) {
+      historySelect.addEventListener('change', () => {
+        if (historySelect.value) {
+          findReplaceInput.value = historySelect.value;
+          refreshFindMatches({ resetIndex: true });
+        }
+      });
     }
-    if (findReplacePrev) {
-      findReplacePrev.addEventListener('click', function() { cycleFindMatch(-1); });
+
+    // Scope select handler
+    const scopeSelect = document.getElementById('find-replace-scope');
+    if (scopeSelect) {
+      scopeSelect.addEventListener('change', () => {
+        refreshFindMatches({ resetIndex: true });
+      });
     }
-    if (findReplaceNext) {
-      findReplaceNext.addEventListener('click', function() { cycleFindMatch(1); });
+
+    // Dock toggle handler
+    const dockBtn = document.getElementById('find-replace-dock');
+    if (dockBtn) {
+      dockBtn.addEventListener('click', toggleFrDockMode);
     }
-    if (findReplaceCurrent) {
-      findReplaceCurrent.addEventListener('click', replaceCurrentMatch);
+
+    // Advanced Drawer Toggle
+    const drawerToggle = document.getElementById('fr-drawer-toggle');
+    const drawerContent = document.getElementById('fr-drawer-content');
+    if (drawerToggle && drawerContent) {
+      drawerToggle.addEventListener('click', () => {
+        const isOpen = drawerContent.style.display === 'flex';
+        if (isOpen) {
+          drawerContent.style.display = 'none';
+          drawerToggle.setAttribute('aria-expanded', 'false');
+          drawerToggle.innerHTML = '<i class="bi bi-chevron-right me-1"></i> Advanced Options';
+        } else {
+          drawerContent.style.display = 'flex';
+          drawerToggle.setAttribute('aria-expanded', 'true');
+          drawerToggle.innerHTML = '<i class="bi bi-chevron-down me-1"></i> Advanced Options';
+        }
+      });
     }
-    if (findReplaceAll) {
-      findReplaceAll.addEventListener('click', replaceAllMatches);
+
+    // Inputs
+    if (findReplaceInput) {
+      findReplaceInput.addEventListener('input', function() {
+        refreshFindMatches({ resetIndex: true });
+      });
+      findReplaceInput.addEventListener('keydown', function(event) {
+        if (event.key === 'Enter') {
+          event.preventDefault();
+          cycleFindMatch(event.shiftKey ? -1 : 1);
+        }
+      });
     }
-    if (findReplaceClose) {
-      findReplaceClose.addEventListener('click', closeFindReplaceModal);
+
+    if (findReplaceWith) {
+      findReplaceWith.addEventListener('input', updateFindControls);
     }
-    if (findReplaceCloseIcon) {
-      findReplaceCloseIcon.addEventListener('click', closeFindReplaceModal);
+
+    // Navigation buttons
+    const prevBtn = document.getElementById('find-prev');
+    const nextBtn = document.getElementById('find-next');
+    if (prevBtn) prevBtn.addEventListener('click', () => cycleFindMatch(-1));
+    if (nextBtn) nextBtn.addEventListener('click', () => cycleFindMatch(1));
+
+    // Action buttons
+    const currentBtn = document.getElementById('find-replace-current');
+    const allBtn = document.getElementById('find-replace-all');
+    if (currentBtn) currentBtn.addEventListener('click', replaceCurrentMatch);
+    if (allBtn) allBtn.addEventListener('click', replaceAllMatches);
+
+    // Close buttons
+    const closeBtn = document.getElementById('find-replace-close');
+    const closeIcon = document.getElementById('find-replace-close-icon');
+    if (closeBtn) closeBtn.addEventListener('click', closeFindReplaceModal);
+    if (closeIcon) closeIcon.addEventListener('click', closeFindReplaceModal);
+
+    // Diff modal confirmation triggers
+    const diffConfirmBtn = document.getElementById('find-replace-diff-confirm');
+    const diffCancelBtn = document.getElementById('find-replace-diff-cancel');
+    const diffCloseIcon = document.getElementById('find-replace-diff-close-icon');
+    const diffModal = document.getElementById('find-replace-diff-modal');
+
+    if (diffConfirmBtn) {
+      diffConfirmBtn.addEventListener('click', () => {
+        executeBulkReplace();
+        closeAppModal(diffModal);
+      });
     }
+    if (diffCancelBtn) diffCancelBtn.addEventListener('click', () => closeAppModal(diffModal));
+    if (diffCloseIcon) diffCloseIcon.addEventListener('click', () => closeAppModal(diffModal));
   }
 
   function initAppModals() {
diff --git a/styles.css b/styles.css
index 2a7ecf2..2e47509 100644
--- a/styles.css
+++ b/styles.css
@@ -1,2948 +1,3377 @@
-:root {
-  --bg-color: #ffffff;
-  --editor-bg: #f6f8fa;
-  --preview-bg: #ffffff; /* Preview background for light mode */
-  --text-color: #24292e;
-  --text-secondary: #57606a;
-  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
-  --color-danger-fg: #d73a49;
-  --preview-text-color: #24292e; /* Text color for preview in light mode */
-  --border-color: #e1e4e8;
-  --header-bg: #f6f8fa;
-  --button-bg: #f6f8fa;
-  --button-hover: #e1e4e8;
-  --button-active: #d1d5da;
-  --scrollbar-thumb: #c1c1c1;
-  --scrollbar-track: #f1f1f1;
-  --accent-color: #0366d6;
-  --table-bg: #ffffff; /* Table background for light mode */
-  --code-bg: #f6f8fa; /* Code block background for light mode */
-}
-
-[data-theme="dark"] {
-  --bg-color: #0d1117;
-  --editor-bg: #161b22;
-  --preview-bg: #0d1117; /* Preview background for dark mode */
-  --text-color: #c9d1d9;
-  --text-secondary: #8b949e;
-  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
-  --color-danger-fg: #f85149;
-  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
-  --border-color: #30363d;
-  --header-bg: #161b22;
-  --button-bg: #21262d;
-  --button-hover: #30363d;
-  --button-active: #3b434b;
-  --scrollbar-thumb: #484f58;
-  --scrollbar-track: #21262d;
-  --accent-color: #58a6ff;
-  --table-bg: #161b22; /* Table background for dark mode */
-  --code-bg: #161b22; /* Code block background for dark mode */
-}
-
-* {
-  box-sizing: border-box;
-  margin: 0;
-  padding: 0;
-}
-
-body {
-  background-color: var(--bg-color);
-  color: var(--text-color);
-  transition: background-color 0.3s ease, color 0.3s ease;
-  min-height: 100vh;
-  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
-}
-
-.app-header {
-  background-color: var(--header-bg);
-  border-bottom: 1px solid var(--border-color);
-  padding: 0.35rem 0.75rem;
-  transition: background-color 0.3s ease;
-  position: relative;
-  z-index: 100;
-  flex-shrink: 0;
-}
-
-.app-container {
-  height: 100vh;
-  display: flex;
-  flex-direction: column;
-  overflow: hidden;
-}
-
-.content-container {
-  display: flex;
-  flex: 1;
-  overflow: hidden;
-}
-
-.editor-pane, .preview-pane {
-  flex: 1;
-  padding: 20px;
-  overflow-y: auto;
-  position: relative;
-  transition: background-color 0.3s ease;
-}
-
-.editor-pane {
-  background-color: var(--editor-bg);
-  border-right: 1px solid var(--border-color);
-  padding-right: 0px;
-  --line-number-gutter: 0px;
-}
-
-.preview-pane {
-  background-color: var(--preview-bg); /* Using the new variable for preview background */
-}
-
-/* Custom scrollbar */
-.editor-pane::-webkit-scrollbar,
-.preview-pane::-webkit-scrollbar,
-#markdown-editor::-webkit-scrollbar {
-  width: 8px;
-  height: 8px;
-}
-
-.editor-pane::-webkit-scrollbar-track,
-.preview-pane::-webkit-scrollbar-track,
-#markdown-editor::-webkit-scrollbar-track {
-  background: var(--scrollbar-track);
-}
-
-.editor-pane::-webkit-scrollbar-thumb,
-.preview-pane::-webkit-scrollbar-thumb,
-#markdown-editor::-webkit-scrollbar-thumb {
-  background: var(--scrollbar-thumb);
-  border-radius: 4px;
-}
-
-.editor-pane::-webkit-scrollbar-thumb:hover,
-.preview-pane::-webkit-scrollbar-thumb:hover,
-#markdown-editor::-webkit-scrollbar-thumb:hover {
-  background: var(--button-active);
-}
-
-#markdown-editor {
-  width: 100%;
-  height: 100%;
-  border: none;
-  background-color: transparent;
-  color: var(--text-color);
-  resize: none;
-  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
-  font-size: 14px;
-  line-height: 1.5;
-  padding: 10px;
-  padding-left: calc(10px + var(--line-number-gutter));
-  transition: background-color 0.3s ease, color 0.3s ease;
-  overflow-y: auto;
-  position: relative;
-  z-index: 3;
-}
-
-#markdown-editor:focus {
-  outline: none;
-}
-
-.preview-pane {
-  padding: 20px;
-}
-
-.markdown-body {
-  padding: 20px;
-  width: 100%;
-  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
-  color: var(--preview-text-color); /* Using specific text color for preview content */
-}
-
-.markdown-body a.reference-link {
-  font-size: 0.75em;
-  letter-spacing: -0.02em;
-  line-height: 1;
-  vertical-align: super;
-  position: relative;
-  top: 0.08em;
-}
-
-/* Style tables in light mode */
-.markdown-body table {
-  background-color: var(--table-bg);
-  border-color: var(--border-color);
-}
-
-.markdown-body table tr {
-  background-color: var(--table-bg);
-  border-top: 1px solid var(--border-color);
-}
-
-.markdown-body table tr:nth-child(2n) {
-  background-color: var(--bg-color);
-}
-
-/* Style code blocks in light mode */
-.markdown-body pre {
-  background-color: var(--code-bg);
-  border-radius: 6px;
-}
-
-.markdown-body code {
-  background-color: var(--code-bg);
-  border-radius: 3px;
-  padding: 0.2em 0.4em;
-}
-
-.markdown-body img.emoji-inline {
-  width: 1em;
-  height: 1em;
-  vertical-align: -0.1em;
-}
-
-.markdown-body ul,
-.markdown-body ol {
-  padding-left: 2em;
-  margin: 0.4em 0;
-}
-
-.markdown-body ul ul,
-.markdown-body ul ol,
-.markdown-body ol ul,
-.markdown-body ol ol {
-  margin-top: 0.2em;
-  margin-bottom: 0.2em;
-}
-
-.markdown-body ul.contains-task-list,
-.markdown-body li.task-list-item {
-  list-style: none;
-}
-
-.markdown-body ul.contains-task-list {
-  padding-left: 2em;
-}
-
-.markdown-body li.task-list-item input[type="checkbox"] {
-  margin: 0 0.5em 0.2em 0;
-  vertical-align: middle;
-  pointer-events: none;
-}
-
-.markdown-body li.task-list-item::marker {
-  content: "";
-}
-
-.markdown-body li:has(> input[type="checkbox"]) {
-  list-style: none;
-}
-
-.markdown-body li:has(> input[type="checkbox"])::marker {
-  content: "";
-}
-
-.markdown-body ul:has(> li > input[type="checkbox"]) {
-  list-style: none;
-  padding-left: 2em;
-}
-
-.markdown-body .footnotes {
-  margin-top: 1.5rem;
-  font-size: 0.9em;
-}
-
-.markdown-body .footnotes ol {
-  padding-left: 1.5em;
-}
-
-.markdown-body .footnotes ol > li::marker {
-  content: "[" counter(list-item) "] ";
-  font-weight: 600;
-}
-
-.markdown-body .footnotes li > p {
-  margin: 0.2em 0;
-}
-
-.markdown-body .footnote-ref a,
-.markdown-body .footnote-backref {
-  text-decoration: none;
-}
-
-.markdown-body .footnote-backref {
-  margin-left: 0.4em;
-}
-
-.markdown-body .markdown-alert {
-  padding: 0.5rem 1rem;
-  margin-bottom: 16px;
-  border-left: 0.25em solid;
-  border-radius: 0.375rem;
-}
-
-.markdown-body .markdown-alert > :last-child {
-  margin-bottom: 0;
-}
-
-.markdown-body .markdown-alert-title {
-  margin: 0 0 8px;
-  font-weight: 600;
-  line-height: 1.25;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-}
-
-.markdown-body .markdown-alert-icon {
-  display: inline-flex;
-  width: 16px;
-  height: 16px;
-}
-
-.markdown-body .markdown-alert-icon svg {
-  width: 16px;
-  height: 16px;
-  fill: currentColor;
-}
-
-.markdown-body .markdown-alert-note {
-  color: #0969da;
-  border-left-color: #0969da;
-  background-color: #ddf4ff;
-}
-
-.markdown-body .markdown-alert-tip {
-  color: #1a7f37;
-  border-left-color: #1a7f37;
-  background-color: #dafbe1;
-}
-
-.markdown-body .markdown-alert-important {
-  color: #8250df;
-  border-left-color: #8250df;
-  background-color: #fbefff;
-}
-
-.markdown-body .markdown-alert-warning {
-  color: #9a6700;
-  border-left-color: #9a6700;
-  background-color: #fff8c5;
-}
-
-.markdown-body .markdown-alert-caution {
-  color: #cf222e;
-  border-left-color: #cf222e;
-  background-color: #ffebe9;
-}
-
-.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
-  color: var(--preview-text-color);
-}
-
-[data-theme="dark"] .markdown-body .markdown-alert-note {
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-  display: flex;
-  gap: 8px;
-  align-items: center;
-}
-
-.share-url-input {
-  flex: 1;
-  font-size: 12px;
-  font-family: var(--font-mono, monospace);
-  color: var(--text-secondary, #57606a);
-  overflow: hidden;
-  text-overflow: ellipsis;
-  white-space: nowrap;
-}
-
-.share-copy-btn {
-  flex-shrink: 0;
-  padding: 6px 10px;
-}
-
-.share-copy-btn:disabled {
-  opacity: 0.5;
-  cursor: not-allowed;
-}
-
-.share-modal-notice {
-  font-size: 11px;
-  color: var(--text-secondary, #57606a);
-  margin: 0;
-  display: flex;
-  align-items: center;
-  gap: 5px;
-}
-
-/* ==========================================================================
-   Multilingual & CJK Optimization styles added by Aegis SEO agency
-   ========================================================================== */
-.lang-select-item {
-  display: flex !important;
-  align-items: center;
-  gap: 8px;
-  cursor: pointer;
-  transition: background-color 0.2s ease, padding-left 0.2s ease;
-}
-
-.lang-select-item:hover {
-  padding-left: 12px;
-}
-
-.lang-select-item.active {
-  background-color: var(--accent-color) !important;
-  color: #ffffff !important;
-  font-weight: 600;
-}
-
-/* Adjust CJK text layout for maximum readability inside the preview pane */
-html[lang="zh"] .markdown-body,
-html[lang="ja"] .markdown-body,
-html[lang="ko"] .markdown-body {
-  line-height: 1.75 !important;
-  letter-spacing: 0.03em;
-  word-break: keep-all;
-  overflow-wrap: break-word;
-  text-align: justify;
-}
-
-/* Specific heading spacing improvements for CJK characters */
-html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
-html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
-html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
-  font-weight: 700;
-  letter-spacing: 0.02em;
-  margin-top: 1.4em;
-  margin-bottom: 0.6em;
-}
-
-/* Smooth fade and scale transition for dropdown active states */
-.dropdown-menu {
-  opacity: 0;
-  transform: translateY(8px) scale(0.98);
-  display: block;
-  visibility: hidden;
-  transition: opacity 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.2s;
-}
-
-.dropdown-menu.show {
-  opacity: 1;
-  transform: translateY(0) scale(1);
-  visibility: visible;
-}
\ No newline at end of file
+:root {
+  --bg-color: #ffffff;
+  --editor-bg: #f6f8fa;
+  --preview-bg: #ffffff; /* Preview background for light mode */
+  --text-color: #24292e;
+  --text-secondary: #57606a;
+  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
+  --color-danger-fg: #d73a49;
+  --preview-text-color: #24292e; /* Text color for preview in light mode */
+  --border-color: #e1e4e8;
+  --header-bg: #f6f8fa;
+  --button-bg: #f6f8fa;
+  --button-hover: #e1e4e8;
+  --button-active: #d1d5da;
+  --scrollbar-thumb: #c1c1c1;
+  --scrollbar-track: #f1f1f1;
+  --accent-color: #0366d6;
+  --table-bg: #ffffff; /* Table background for light mode */
+  --code-bg: #f6f8fa; /* Code block background for light mode */
+}
+
+[data-theme="dark"] {
+  --bg-color: #0d1117;
+  --editor-bg: #161b22;
+  --preview-bg: #0d1117; /* Preview background for dark mode */
+  --text-color: #c9d1d9;
+  --text-secondary: #8b949e;
+  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
+  --color-danger-fg: #f85149;
+  --preview-text-color: #c9d1d9; /* Text color for preview in dark mode */
+  --border-color: #30363d;
+  --header-bg: #161b22;
+  --button-bg: #21262d;
+  --button-hover: #30363d;
+  --button-active: #3b434b;
+  --scrollbar-thumb: #484f58;
+  --scrollbar-track: #21262d;
+  --accent-color: #58a6ff;
+  --table-bg: #161b22; /* Table background for dark mode */
+  --code-bg: #161b22; /* Code block background for dark mode */
+}
+
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+body {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  transition: background-color 0.3s ease, color 0.3s ease;
+  min-height: 100vh;
+  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Hiragino Kaku Gothic ProN", Meiryo, "Malgun Gothic", "Apple SD Gothic Neo", "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
+}
+
+.app-header {
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  padding: 0.35rem 0.75rem;
+  transition: background-color 0.3s ease;
+  position: relative;
+  z-index: 100;
+  flex-shrink: 0;
+}
+
+.app-container {
+  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+}
+
+.editor-pane, .preview-pane {
+  flex: 1;
+  padding: 20px;
+  overflow-y: auto;
+  position: relative;
+  transition: background-color 0.3s ease;
+}
+
+.editor-pane {
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  padding-right: 0px;
+  --line-number-gutter: 0px;
+}
+
+.preview-pane {
+  background-color: var(--preview-bg); /* Using the new variable for preview background */
+}
+
+/* Custom scrollbar */
+.editor-pane::-webkit-scrollbar,
+.preview-pane::-webkit-scrollbar,
+#markdown-editor::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-pane::-webkit-scrollbar-track,
+.preview-pane::-webkit-scrollbar-track,
+#markdown-editor::-webkit-scrollbar-track {
+  background: var(--scrollbar-track);
+}
+
+.editor-pane::-webkit-scrollbar-thumb,
+.preview-pane::-webkit-scrollbar-thumb,
+#markdown-editor::-webkit-scrollbar-thumb {
+  background: var(--scrollbar-thumb);
+  border-radius: 4px;
+}
+
+.editor-pane::-webkit-scrollbar-thumb:hover,
+.preview-pane::-webkit-scrollbar-thumb:hover,
+#markdown-editor::-webkit-scrollbar-thumb:hover {
+  background: var(--button-active);
+}
+
+#markdown-editor {
+  width: 100%;
+  height: 100%;
+  border: none;
+  background-color: transparent;
+  color: var(--text-color);
+  resize: none;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  padding: 10px;
+  padding-left: calc(10px + var(--line-number-gutter));
+  transition: background-color 0.3s ease, color 0.3s ease;
+  overflow-y: auto;
+  position: relative;
+  z-index: 3;
+}
+
+#markdown-editor:focus {
+  outline: none;
+}
+
+.preview-pane {
+  padding: 20px;
+}
+
+.markdown-body {
+  padding: 20px;
+  width: 100%;
+  background-color: var(--preview-bg); /* Ensuring the markdown content matches preview background */
+  color: var(--preview-text-color); /* Using specific text color for preview content */
+}
+
+.markdown-body a.reference-link {
+  font-size: 0.75em;
+  letter-spacing: -0.02em;
+  line-height: 1;
+  vertical-align: super;
+  position: relative;
+  top: 0.08em;
+}
+
+/* Style tables in light mode */
+.markdown-body table {
+  background-color: var(--table-bg);
+  border-color: var(--border-color);
+}
+
+.markdown-body table tr {
+  background-color: var(--table-bg);
+  border-top: 1px solid var(--border-color);
+}
+
+.markdown-body table tr:nth-child(2n) {
+  background-color: var(--bg-color);
+}
+
+/* Style code blocks in light mode */
+.markdown-body pre {
+  background-color: var(--code-bg);
+  border-radius: 6px;
+}
+
+.markdown-body code {
+  background-color: var(--code-bg);
+  border-radius: 3px;
+  padding: 0.2em 0.4em;
+}
+
+.markdown-body img.emoji-inline {
+  width: 1em;
+  height: 1em;
+  vertical-align: -0.1em;
+}
+
+.markdown-body ul,
+.markdown-body ol {
+  padding-left: 2em;
+  margin: 0.4em 0;
+}
+
+.markdown-body ul ul,
+.markdown-body ul ol,
+.markdown-body ol ul,
+.markdown-body ol ol {
+  margin-top: 0.2em;
+  margin-bottom: 0.2em;
+}
+
+.markdown-body ul.contains-task-list,
+.markdown-body li.task-list-item {
+  list-style: none;
+}
+
+.markdown-body ul.contains-task-list {
+  padding-left: 2em;
+}
+
+.markdown-body li.task-list-item input[type="checkbox"] {
+  margin: 0 0.5em 0.2em 0;
+  vertical-align: middle;
+  pointer-events: none;
+}
+
+.markdown-body li.task-list-item::marker {
+  content: "";
+}
+
+.markdown-body li:has(> input[type="checkbox"]) {
+  list-style: none;
+}
+
+.markdown-body li:has(> input[type="checkbox"])::marker {
+  content: "";
+}
+
+.markdown-body ul:has(> li > input[type="checkbox"]) {
+  list-style: none;
+  padding-left: 2em;
+}
+
+.markdown-body .footnotes {
+  margin-top: 1.5rem;
+  font-size: 0.9em;
+}
+
+.markdown-body .footnotes ol {
+  padding-left: 1.5em;
+}
+
+.markdown-body .footnotes ol > li::marker {
+  content: "[" counter(list-item) "] ";
+  font-weight: 600;
+}
+
+.markdown-body .footnotes li > p {
+  margin: 0.2em 0;
+}
+
+.markdown-body .footnote-ref a,
+.markdown-body .footnote-backref {
+  text-decoration: none;
+}
+
+.markdown-body .footnote-backref {
+  margin-left: 0.4em;
+}
+
+.markdown-body .markdown-alert {
+  padding: 0.5rem 1rem;
+  margin-bottom: 16px;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.markdown-body .markdown-alert > :last-child {
+  margin-bottom: 0;
+}
+
+.markdown-body .markdown-alert-title {
+  margin: 0 0 8px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.markdown-body .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.markdown-body .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.markdown-body .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.markdown-body .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.markdown-body .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.markdown-body .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.markdown-body .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+.markdown-body .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--preview-text-color);
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-note {
+  color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+  border-left-color: #4493f8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-tip {
+  color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+  border-left-color: #3fb950;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-important {
+  color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+  border-left-color: #ab7df8;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-warning {
+  color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+  border-left-color: #d29922;
+}
+
+[data-theme="dark"] .markdown-body .markdown-alert-caution {
+  color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+  border-left-color: #f85149;
+}
+
+.toolbar {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.toolbar-group {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+}
+
+.toolbar-divider {
+  width: 1px;
+  height: 20px;
+  background-color: var(--border-color);
+  opacity: 0.7;
+}
+
+.tool-button {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 5px;
+  padding: 4px 8px;
+  font-size: 13px;
+  cursor: pointer;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  transition: all 0.2s ease;
+}
+
+.tool-button:hover {
+  background-color: var(--button-hover);
+}
+
+.tool-button:active {
+  background-color: var(--button-active);
+}
+
+.tool-button:disabled,
+.tool-button[aria-disabled="true"] {
+  cursor: not-allowed;
+  opacity: 0.5;
+}
+
+.tool-button i {
+  font-size: 15px;
+}
+
+.tool-button.is-active,
+.tool-button.is-active:hover {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: rgba(3, 102, 214, 0.08);
+}
+
+.btn-text {
+  display: none;
+}
+
+.toolbar .tool-button {
+  height: 28px;
+  min-width: 28px;
+}
+
+.toolbar .tool-button.sync-active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+}
+
+.file-input {
+  display: none;
+}
+
+/* Drag overlay: full-screen drop target shown when user drags a file over the window */
+.drag-overlay {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 9999;
+  background-color: rgba(0, 0, 0, 0.45);
+  pointer-events: none;
+  align-items: center;
+  justify-content: center;
+}
+
+.drag-overlay.active {
+  display: flex;
+  pointer-events: auto;
+}
+
+.drag-overlay-inner {
+  border: 3px dashed var(--accent-color);
+  border-radius: 12px;
+  padding: 48px 64px;
+  text-align: center;
+  color: #ffffff;
+  background-color: rgba(3, 102, 214, 0.15);
+  animation: overlayPulse 1.4s ease-in-out infinite;
+}
+
+.drag-overlay-icon {
+  display: block;
+  font-size: 3rem;
+  margin-bottom: 12px;
+  color: var(--accent-color);
+}
+
+.drag-overlay-text {
+  font-size: 1.4rem;
+  font-weight: 600;
+  margin-bottom: 4px;
+}
+
+.drag-overlay-sub {
+  font-size: 0.85rem;
+  opacity: 0.75;
+  margin-bottom: 0;
+}
+
+@keyframes overlayPulse {
+  0%, 100% { transform: scale(1); }
+  50% { transform: scale(1.015); }
+}
+
+/* Editor drop hint: subtle text at bottom of editor pane, shown only when empty */
+.drop-hint {
+  position: absolute;
+  bottom: 14px;
+  left: 0;
+  right: 0;
+  text-align: center;
+  font-size: 0.75rem;
+  color: var(--text-color);
+  opacity: 0.35;
+  pointer-events: none;
+  user-select: none;
+  z-index: 3;
+}
+
+.editor-pane:has(#markdown-editor:not(:placeholder-shown)) .drop-hint {
+  display: none;
+}
+
+.line-numbers {
+  position: absolute;
+  top: 20px;
+  bottom: 20px;
+  left: 20px;
+  width: var(--line-number-gutter);
+  padding: 10px 8px 10px 0;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  text-align: right;
+  color: var(--text-color);
+  opacity: 0.55;
+  background-color: var(--editor-bg);
+  border-right: 1px solid var(--border-color);
+  box-sizing: border-box;
+  overflow: hidden;
+  pointer-events: none;
+  user-select: none;
+  z-index: 2;
+  font-variant-numeric: tabular-nums;
+}
+
+.line-numbers .line-number {
+  display: block;
+  height: auto;
+}
+
+.editor-highlight-layer {
+  position: absolute;
+  inset: 20px 0 20px calc(20px + var(--line-number-gutter));
+  padding: 10px;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 14px;
+  line-height: 1.5;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+  color: transparent;
+  pointer-events: none;
+  overflow: auto;
+  background-color: var(--editor-bg);
+  border-radius: 4px;
+  z-index: 1;
+}
+
+.editor-highlight-layer::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-thumb {
+  background: transparent;
+}
+
+.editor-highlight-layer::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+.find-highlight {
+  background-color: rgba(255, 196, 0, 0.35);
+  border-radius: 2px;
+}
+
+.find-highlight.active {
+  background-color: rgba(255, 196, 0, 0.65);
+}
+
+/* Dropdown improvements */
+.dropdown-menu {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+}
+
+.dropdown-item {
+  color: var(--text-color);
+}
+
+.dropdown-item:hover, .dropdown-item:focus {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+/* Markdown formatting toolbar */
+.markdown-format-toolbar {
+  display: flex;
+  align-items: center;
+  height: 34px;
+  padding: 0 6px;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  overflow-x: auto;
+  overflow-y: hidden;
+  flex-shrink: 0;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.markdown-format-toolbar::-webkit-scrollbar {
+  display: none;
+}
+
+.markdown-toolbar-group {
+  display: flex;
+  align-items: center;
+  gap: 2px;
+  height: 100%;
+  padding: 0 6px;
+  border-right: 1px solid var(--border-color);
+  flex-shrink: 0;
+}
+
+.markdown-toolbar-group:first-child {
+  padding-left: 0;
+}
+
+.markdown-toolbar-group:last-child {
+  border-right: none;
+  padding-right: 0;
+}
+
+.markdown-tool-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 26px;
+  height: 26px;
+  border: 1px solid transparent;
+  border-radius: 4px;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 14px;
+  line-height: 1;
+  padding: 0;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.markdown-tool-btn:hover,
+.markdown-tool-btn:focus-visible {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+}
+
+.markdown-tool-btn:active {
+  background-color: var(--button-active);
+}
+
+.markdown-tool-btn i {
+  font-size: 15px;
+}
+
+.markdown-tool-btn[data-md-action="reference"] i::before {
+  content: "[ ]";
+  font-style: normal;
+  font-size: 12px;
+  letter-spacing: -0.12em;
+}
+
+.markdown-tool-btn.text-tool {
+  width: auto;
+  min-width: 26px;
+  padding: 0 5px;
+  font-weight: 600;
+  font-family: Georgia, "Times New Roman", serif;
+}
+
+.heading-group .markdown-tool-btn {
+  min-width: 30px;
+}
+
+
+
+/* Loading indicators */
+.loading {
+  opacity: 0.6;
+  pointer-events: none;
+}
+
+/* Focus outline for accessibility */
+button:focus, 
+a:focus {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+/* Animation for copied message */
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+/* Tooltip styles */
+.tooltip {
+  position: absolute;
+  background: var(--button-bg);
+  border: 1px solid var(--border-color);
+  padding: 5px 8px;
+  border-radius: 4px;
+  font-size: 12px;
+  z-index: 1000;
+  animation: fadeIn 0.2s ease;
+}
+
+/* Styles for GitHub markdown preview light mode */
+.markdown-body {
+  color-scheme: light;
+  --color-prettylights-syntax-comment: #6a737d;
+  --color-prettylights-syntax-constant: #005cc5;
+  --color-prettylights-syntax-entity: #6f42c1;
+  --color-prettylights-syntax-storage-modifier-import: #24292e;
+  --color-prettylights-syntax-entity-tag: #22863a;
+  --color-prettylights-syntax-keyword: #d73a49;
+  --color-prettylights-syntax-string: #032f62;
+  --color-prettylights-syntax-variable: #e36209;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #b31d28;
+  --color-prettylights-syntax-invalid-illegal-text: #fafbfc;
+  --color-prettylights-syntax-invalid-illegal-bg: #b31d28;
+  --color-prettylights-syntax-carriage-return-text: #fafbfc;
+  --color-prettylights-syntax-carriage-return-bg: #d73a49;
+  --color-prettylights-syntax-string-regexp: #22863a;
+  --color-prettylights-syntax-markup-list: #735c0f;
+  --color-prettylights-syntax-markup-heading: #005cc5;
+  --color-prettylights-syntax-markup-italic: #24292e;
+  --color-prettylights-syntax-markup-bold: #24292e;
+  --color-prettylights-syntax-markup-deleted-text: #b31d28;
+  --color-prettylights-syntax-markup-deleted-bg: #ffeef0;
+  --color-prettylights-syntax-markup-inserted-text: #22863a;
+  --color-prettylights-syntax-markup-inserted-bg: #f0fff4;
+  --color-prettylights-syntax-markup-changed-text: #e36209;
+  --color-prettylights-syntax-markup-changed-bg: #ffebda;
+  --color-prettylights-syntax-markup-ignored-text: #f6f8fa;
+  --color-prettylights-syntax-markup-ignored-bg: #005cc5;
+  --color-prettylights-syntax-meta-diff-range: #6f42c1;
+  --color-prettylights-syntax-brackethighlighter-angle: #586069;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #e1e4e8;
+  --color-prettylights-syntax-constant-other-reference-link: #032f62;
+  --color-fg-default: #24292e;
+  --color-fg-muted: #586069;
+  --color-fg-subtle: #6a737d;
+  --color-canvas-default: #ffffff;
+  --color-canvas-subtle: #f6f8fa;
+  --color-border-default: #e1e4e8;
+  --color-border-muted: #eaecef;
+  --color-neutral-muted: rgba(175,184,193,0.2);
+  --color-accent-fg: #0366d6;
+  --color-accent-emphasis: #0366d6;
+  --color-attention-subtle: #fff5b1;
+  --color-danger-fg: #d73a49;
+}
+
+/* Styles for GitHub markdown preview dark mode */
+[data-theme="dark"] .markdown-body {
+  color-scheme: dark;
+  --color-prettylights-syntax-comment: #8b949e;
+  --color-prettylights-syntax-constant: #79c0ff;
+  --color-prettylights-syntax-entity: #d2a8ff;
+  --color-prettylights-syntax-storage-modifier-import: #c9d1d9;
+  --color-prettylights-syntax-entity-tag: #7ee787;
+  --color-prettylights-syntax-keyword: #ff7b72;
+  --color-prettylights-syntax-string: #a5d6ff;
+  --color-prettylights-syntax-variable: #ffa657;
+  --color-prettylights-syntax-brackethighlighter-unmatched: #f85149;
+  --color-prettylights-syntax-invalid-illegal-text: #f0f6fc;
+  --color-prettylights-syntax-invalid-illegal-bg: #8e1519;
+  --color-prettylights-syntax-carriage-return-text: #f0f6fc;
+  --color-prettylights-syntax-carriage-return-bg: #b62324;
+  --color-prettylights-syntax-string-regexp: #7ee787;
+  --color-prettylights-syntax-markup-list: #f2cc60;
+  --color-prettylights-syntax-markup-heading: #1f6feb;
+  --color-prettylights-syntax-markup-italic: #c9d1d9;
+  --color-prettylights-syntax-markup-bold: #c9d1d9;
+  --color-prettylights-syntax-markup-deleted-text: #ffdcd7;
+  --color-prettylights-syntax-markup-deleted-bg: #67060c;
+  --color-prettylights-syntax-markup-inserted-text: #aff5b4;
+  --color-prettylights-syntax-markup-inserted-bg: #033a16;
+  --color-prettylights-syntax-markup-changed-text: #ffdfb6;
+  --color-prettylights-syntax-markup-changed-bg: #5a1e02;
+  --color-prettylights-syntax-markup-ignored-text: #c9d1d9;
+  --color-prettylights-syntax-markup-ignored-bg: #1158c7;
+  --color-prettylights-syntax-meta-diff-range: #d2a8ff;
+  --color-prettylights-syntax-brackethighlighter-angle: #8b949e;
+  --color-prettylights-syntax-sublimelinter-gutter-mark: #484f58;
+  --color-prettylights-syntax-constant-other-reference-link: #a5d6ff;
+  --color-fg-default: #c9d1d9;
+  --color-fg-muted: #8b949e;
+  --color-fg-subtle: #484f58;
+  --color-canvas-default: #0d1117;
+  --color-canvas-subtle: #161b22;
+  --color-border-default: #30363d;
+  --color-border-muted: #21262d;
+  --color-neutral-muted: rgba(110,118,129,0.4);
+  --color-accent-fg: #58a6ff;
+  --color-accent-emphasis: #1f6feb;
+  --color-attention-subtle: rgba(187,128,9,0.15);
+  --color-danger-fg: #f85149;
+}
+
+/* Override specific styles for dark mode tables and code */
+[data-theme="dark"] .markdown-body table tr {
+  background-color: var(--table-bg);
+}
+
+[data-theme="dark"] .markdown-body table tr:nth-child(2n) {
+  background-color: #1c2128; /* Slightly lighter than base dark background */
+}
+
+[data-theme="dark"] .markdown-body pre {
+  background-color: var(--code-bg);
+}
+
+[data-theme="dark"] .markdown-body code {
+  background-color: var(--code-bg);
+}
+
+/* Syntax Highlighting Mapping to GitHub Variables */
+.hljs {
+  color: var(--color-fg-default);
+}
+.hljs-doctag,
+.hljs-keyword,
+.hljs-meta .hljs-keyword,
+.hljs-template-tag,
+.hljs-template-variable,
+.hljs-type,
+.hljs-variable.language_ {
+  color: var(--color-prettylights-syntax-keyword);
+}
+.hljs-title,
+.hljs-title.class_,
+.hljs-title.class_.inherited__,
+.hljs-title.function_ {
+  color: var(--color-prettylights-syntax-entity);
+}
+.hljs-attr,
+.hljs-attribute,
+.hljs-literal,
+.hljs-meta,
+.hljs-number,
+.hljs-operator,
+.hljs-variable,
+.hljs-selector-attr,
+.hljs-selector-class,
+.hljs-selector-id {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-regexp,
+.hljs-string,
+.hljs-meta .hljs-string {
+  color: var(--color-prettylights-syntax-string);
+}
+.hljs-built_in,
+.hljs-symbol {
+  color: var(--color-prettylights-syntax-variable);
+}
+.hljs-comment,
+.hljs-code,
+.hljs-formula {
+  color: var(--color-prettylights-syntax-comment);
+}
+.hljs-name,
+.hljs-quote,
+.hljs-selector-tag,
+.hljs-selector-pseudo {
+  color: var(--color-prettylights-syntax-entity-tag);
+}
+.hljs-subst {
+  color: var(--color-fg-default);
+}
+.hljs-section {
+  color: var(--color-prettylights-syntax-markup-heading);
+  font-weight: bold;
+}
+.hljs-bullet {
+  color: var(--color-prettylights-syntax-constant);
+}
+.hljs-emphasis {
+  color: var(--color-fg-default);
+  font-style: italic;
+}
+.hljs-strong {
+  color: var(--color-fg-default);
+  font-weight: bold;
+}
+.hljs-addition {
+  color: var(--color-prettylights-syntax-markup-inserted-text);
+  background-color: var(--color-prettylights-syntax-markup-inserted-bg);
+}
+.hljs-deletion {
+  color: var(--color-prettylights-syntax-markup-deleted-text);
+  background-color: var(--color-prettylights-syntax-markup-deleted-bg);
+}
+
+.stats-container {
+  font-size: 0.8rem;
+  color: var(--text-color);
+}
+
+.stat-item {
+  align-items: center;
+}
+
+.stat-item i {
+  font-size: 0.9rem;
+  opacity: 0.8;
+}
+
+#importDropdown,
+#exportDropdown,
+#languageDropdown {
+  font-size: 0.8rem;
+}
+
+#importDropdown i,
+#exportDropdown i,
+#languageDropdown i {
+  font-size: 0.9rem;
+}
+
+/* Ensure desktop dropdown menu options match the stats-container font size */
+[aria-labelledby="importDropdown"] .dropdown-item,
+[aria-labelledby="exportDropdown"] .dropdown-item,
+[aria-labelledby="languageDropdown"] .dropdown-item {
+  font-size: 0.8rem;
+}
+
+/* Ensure mobile menu import, export, and language dropdown triggers/options match the mobile stats-container font size */
+#mobile-import-button,
+#mobile-import-github-button,
+#mobile-export-md,
+#mobile-export-html,
+#mobile-export-pdf,
+#mobileLanguageDropdown {
+  font-size: 0.9rem !important;
+}
+
+[aria-labelledby="mobileLanguageDropdown"] .dropdown-item {
+  font-size: 0.9rem;
+}
+
+.editor-pane {
+  overflow: hidden;
+}
+
+/* Mobile Menu Styles */
+.mobile-menu {
+  display: none;
+  position: relative;
+  z-index: 1001;
+}
+
+
+
+/* slide‑in panel */
+.mobile-menu-panel {
+  position: fixed;
+  top: 0;
+  right: -300px;
+  width: 280px;
+  height: 100vh;
+  background-color: var(--bg-color);
+  box-shadow: -2px 0 10px rgba(0, 0, 0, 0.2);
+  transition: right 0.3s ease;
+  overflow-y: auto;
+  padding: 1rem;
+  display: flex;
+  flex-direction: column;
+  z-index: 1002;
+}
+
+.mobile-menu-panel.active {
+  right: 0;
+}
+
+/* translucent overlay behind panel */
+.mobile-menu-overlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100vh;
+  background-color: rgba(0, 0, 0, 0.5);
+  opacity: 0;
+  visibility: hidden;
+  pointer-events: none;
+  transition: opacity 0.3s ease, visibility 0.3s ease;
+  z-index: 1000;
+}
+
+.mobile-menu-overlay.active {
+  opacity: 1;
+  visibility: visible;
+  pointer-events: auto;
+}
+
+/* header inside mobile menu */
+.mobile-menu-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 1rem;
+}
+
+.mobile-menu-header h5 {
+  margin: 0;
+  font-size: 1.25rem;
+  color: var(--text-color);
+}
+
+/* stats section in mobile menu */
+.mobile-stats-container {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+  margin-bottom: 1rem;
+}
+
+.mobile-stats-container .stat-item {
+  font-size: 0.9rem;
+  color: var(--text-color);
+  display: flex;
+  align-items: center;
+}
+
+.mobile-stats-container .stat-item i {
+  margin-right: 0.5em;
+  opacity: 0.8;
+}
+
+/* menu buttons list */
+.mobile-menu-items {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  flex-grow: 1;
+}
+
+/* each menu item */
+.mobile-menu-item {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 6px;
+  padding: 0.6rem 1rem;
+  font-size: 1rem;
+  text-align: left;
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  transition: background-color 0.2s ease;
+  cursor: pointer;
+}
+
+.mobile-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-menu-item:active {
+  background-color: var(--button-active);
+}
+
+/* close button override */
+#close-mobile-menu.tool-button {
+  padding: 0.25rem 0.5rem;
+  font-size: 1rem;
+}
+
+/* Mobile document tabs section */
+.mobile-tabs-section {
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-tabs-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 0.5rem;
+}
+
+.mobile-tabs-label {
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--text-color);
+  opacity: 0.8;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+.mobile-new-tab-btn {
+  background: none;
+  border: 1px solid var(--border-color);
+  border-radius: 4px;
+  color: var(--text-color);
+  padding: 2px 7px;
+  font-size: 0.9rem;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.15s ease;
+}
+
+.mobile-new-tab-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-list {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  max-height: 180px;
+  overflow-y: auto;
+}
+
+.mobile-tab-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  padding: 0.45rem 0.75rem;
+  font-size: 0.9rem;
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+  gap: 0.5rem;
+}
+
+.mobile-tab-item:hover {
+  background-color: var(--button-hover);
+}
+
+.mobile-tab-item.active {
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  background-color: var(--bg-color);
+}
+
+.mobile-tab-title {
+  flex: 1;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  min-width: 0;
+}
+
+.mobile-tab-item .tab-menu-btn {
+  opacity: 0.6;
+}
+
+.mobile-tab-item:hover .tab-menu-btn,
+.mobile-tab-item.active .tab-menu-btn {
+  opacity: 0.8;
+}
+
+#mobile-tab-reset-btn {
+  margin-left: 0;
+  height: auto;
+  padding: 0.45rem 0.75rem;
+  justify-content: center;
+  font-size: 0.9rem;
+}
+
+/* ==========================================
+   NAVBAR RESPONSIVE BREAKPOINTS
+   >= 1080px : full desktop navbar
+   <  1080px : mobile hamburger + stacked panes
+   ========================================== */
+
+/* Mobile / tablet (< 1080px): switch to hamburger, stack panes */
+@media (max-width: 1079px) {
+  /* Override Bootstrap d-md-flex / d-md-none so the breakpoint is 1080px */
+  .stats-container,
+  .toolbar {
+    display: none !important;
+  }
+
+  /* Expand touch target sizes to meet WCAG mobile guidelines */
+  .markdown-tool-btn {
+    width: 36px !important;
+    height: 36px !important;
+    font-size: 16px !important;
+  }
+  .markdown-format-toolbar {
+    height: 44px !important;
+  }
+  .tab-close-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+  .tab-menu-btn {
+    width: 28px !important;
+    height: 28px !important;
+    font-size: 14px !important;
+  }
+
+  .mobile-menu {
+    display: block !important;
+  }
+
+  /* Stack editor and preview vertically */
+  .content-container {
+    flex-direction: column;
+  }
+
+  .editor-pane,
+  .preview-pane {
+    flex: none;
+    height: 50%;
+    border-right: none;
+  }
+
+  .editor-pane {
+    border-bottom: 1px solid var(--border-color);
+  }
+
+  /* Hide drag-resize divider (touch devices don't use it) */
+  .resize-divider {
+    display: none;
+  }
+
+  /* Single-pane view modes: occupy full height */
+  .content-container.view-editor-only .editor-pane,
+  .content-container.view-preview-only .preview-pane {
+    height: 100%;
+  }
+
+  .content-container.view-split .editor-pane,
+  .content-container.view-split .preview-pane {
+    height: 50%;
+  }
+}
+
+.github-link {
+  color: var(--text-color);
+  text-decoration: none;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: transform 0.2s ease, color 0.2s ease;
+  margin-right: 2rem;
+}
+
+.github-link:hover {
+  color: var(--accent-color);
+  transform: scale(1.1);
+}
+
+.github-link i {
+  font-size: 1.25rem;
+}
+
+/* ========================================
+   HEADER LAYOUT
+   ======================================== */
+.header-container {
+  position: relative;
+  min-height: 30px;
+}
+
+.app-header h1 {
+  font-size: 1.05rem;
+  line-height: 1.1;
+}
+
+.header-left {
+  flex: 1 0 auto;
+  justify-content: flex-start;
+  white-space: nowrap;
+}
+
+.header-right {
+  flex: 1 0 auto;
+  justify-content: flex-end;
+  white-space: nowrap;
+}
+
+/* Pane View States */
+.content-container.view-editor-only .preview-pane {
+  display: none;
+}
+
+.content-container.view-editor-only .editor-pane {
+  flex: 1;
+  border-right: none;
+}
+
+.content-container.view-preview-only .editor-pane {
+  display: none;
+}
+
+.content-container.view-preview-only .preview-pane {
+  flex: 1;
+}
+
+.content-container.view-split .editor-pane,
+.content-container.view-split .preview-pane {
+  flex: 1;
+}
+
+/* Compact desktop (< 1280px): compact toolbar */
+@media (max-width: 1280px) {
+  /* Compact toolbar at medium widths */
+  .toolbar {
+    gap: 4px;
+  }
+}
+
+
+
+/* ========================================
+   RESIZE DIVIDER - Story 1.3
+   ======================================== */
+
+.resize-divider {
+  width: 8px;
+  background-color: transparent;
+  cursor: col-resize;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+  position: relative;
+  z-index: 10;
+  transition: background-color 0.2s ease;
+}
+
+.resize-divider:hover {
+  background-color: var(--button-hover);
+}
+
+.resize-divider.dragging {
+  background-color: var(--accent-color);
+}
+
+.resize-divider-handle {
+  width: 2px;
+  height: 40px;
+  background-color: var(--border-color);
+  border-radius: 2px;
+  transition: background-color 0.2s ease, width 0.2s ease;
+}
+
+.resize-divider:hover .resize-divider-handle,
+.resize-divider.dragging .resize-divider-handle {
+  background-color: var(--accent-color);
+  width: 3px;
+}
+
+/* Hide divider in single-pane modes */
+.content-container.view-editor-only .resize-divider,
+.content-container.view-preview-only .resize-divider {
+  display: none;
+}
+
+
+
+/* Prevent text selection during drag */
+.resizing {
+  user-select: none;
+  cursor: col-resize !important;
+}
+
+.resizing * {
+  cursor: col-resize !important;
+}
+
+.resizing #markdown-preview,
+.resizing #markdown-editor,
+.resizing .line-numbers {
+  pointer-events: none !important;
+}
+
+/* ========================================
+   MOBILE VIEW MODE CONTROLS - Story 1.4
+   ======================================== */
+
+.mobile-view-mode-group {
+  display: flex;
+  gap: 0;
+  border-bottom: 1px solid var(--border-color);
+  padding-bottom: 0.75rem;
+}
+
+.mobile-view-mode-btn {
+  flex: 1;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  padding: 8px 12px;
+  font-size: 14px;
+  cursor: pointer;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 4px;
+  transition: all 0.2s ease;
+}
+
+.mobile-view-mode-btn:first-child {
+  border-radius: 6px 0 0 6px;
+}
+
+.mobile-view-mode-btn:last-child {
+  border-radius: 0 6px 6px 0;
+}
+
+.mobile-view-mode-btn:not(:last-child) {
+  border-right: none;
+}
+
+.mobile-view-mode-btn:hover,
+.mobile-view-mode-btn:active {
+  background-color: var(--button-hover);
+}
+
+.mobile-view-mode-btn.active {
+  background-color: var(--button-bg);
+  border-color: var(--accent-color);
+  color: var(--accent-color);
+  border-width: 2px;
+  padding: 7px 11px;
+}
+
+.mobile-view-mode-btn.active:not(:last-child) {
+  border-right: 2px solid var(--accent-color);
+}
+
+.mobile-view-mode-btn i {
+  font-size: 18px;
+}
+
+.mobile-view-mode-btn span {
+  font-size: 12px;
+}
+
+/* ========================================
+   RESPONSIVE VIEW MODE FIXES - Story 1.5
+   ======================================== */
+
+
+
+/* ========================================
+   PDF EXPORT TABLE FIX - Rowspan/Colspan
+   ======================================== */
+
+/* Fix for html2canvas not properly rendering rowspan/colspan cells.
+   Apply backgrounds to cells instead of rows to prevent row backgrounds
+   from painting over rowspan cells during canvas capture. */
+.pdf-export table tr {
+  background-color: transparent !important;
+}
+
+.pdf-export table th,
+.pdf-export table td {
+  background-color: var(--table-bg, #ffffff);
+  position: relative;
+}
+
+.pdf-export table tr:nth-child(2n) th,
+.pdf-export table tr:nth-child(2n) td {
+  background-color: var(--bg-color, #f6f8fa);
+}
+
+/* Ensure rowspan cells render correctly */
+.pdf-export table th[rowspan],
+.pdf-export table td[rowspan] {
+  vertical-align: middle;
+  background-color: var(--table-bg, #ffffff) !important;
+}
+
+/* Ensure colspan cells render correctly */
+.pdf-export table th[colspan],
+.pdf-export table td[colspan] {
+  text-align: center;
+}
+
+/* Dark mode PDF export table fix */
+[data-theme="dark"] .pdf-export table th,
+[data-theme="dark"] .pdf-export table td {
+  background-color: var(--table-bg, #161b22);
+}
+
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) th,
+[data-theme="dark"] .pdf-export table tr:nth-child(2n) td {
+  background-color: #1c2128;
+}
+
+[data-theme="dark"] .pdf-export table th[rowspan],
+[data-theme="dark"] .pdf-export table td[rowspan] {
+  background-color: var(--table-bg, #161b22) !important;
+}
+
+/* ========================================
+   MERMAID DIAGRAM TOOLBAR
+   ======================================== */
+
+.mermaid-container {
+  position: relative;
+}
+
+.mermaid-toolbar {
+  position: absolute;
+  top: 8px;
+  right: 8px;
+  display: flex;
+  gap: 4px;
+  opacity: 0;
+  transition: opacity 0.2s ease;
+  z-index: 10;
+}
+
+.mermaid-container:hover .mermaid-toolbar {
+  opacity: 1;
+}
+
+.mermaid-toolbar-btn {
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  border-radius: 4px;
+  padding: 4px 7px;
+  font-size: 13px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  gap: 3px;
+  transition: background-color 0.2s ease, color 0.2s ease;
+  white-space: nowrap;
+}
+
+.mermaid-toolbar-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--accent-color);
+}
+
+.mermaid-toolbar-btn:active {
+  background-color: var(--button-active);
+}
+
+.mermaid-toolbar-btn i {
+  font-size: 14px;
+}
+
+/* ========================================
+   MERMAID ZOOM MODAL
+   ======================================== */
+
+#mermaid-zoom-modal {
+  display: none;
+  position: fixed;
+  inset: 0;
+  z-index: 2000;
+  background-color: rgba(0, 0, 0, 0.75);
+  align-items: center;
+  justify-content: center;
+}
+
+#mermaid-zoom-modal.active {
+  display: flex;
+}
+
+.mermaid-modal-content {
+  background-color: var(--bg-color);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  padding: 16px;
+  width: 85vw;
+  height: 85vh;
+  max-width: 85vw;
+  max-height: 85vh;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+@media (max-width: 576px) {
+  .mermaid-modal-content {
+    width: 95vw;
+    height: 90vh;
+    max-width: 95vw;
+    max-height: 90vh;
+    padding: 10px;
+  }
+}
+
+.mermaid-modal-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.mermaid-modal-header span {
+  font-weight: 600;
+  font-size: 15px;
+  color: var(--text-color);
+}
+
+.mermaid-modal-close {
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 1.2rem;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  transition: background-color 0.2s ease;
+}
+
+.mermaid-modal-close:hover {
+  background-color: var(--button-hover);
+}
+
+.mermaid-modal-diagram {
+  overflow: auto;
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 200px;
+  cursor: grab;
+}
+
+.mermaid-modal-diagram.dragging {
+  cursor: grabbing;
+}
+
+.mermaid-modal-diagram svg {
+  transform-origin: center;
+  transition: transform 0.1s ease;
+  max-width: none;
+}
+
+.mermaid-modal-controls {
+  display: flex;
+  justify-content: center;
+  gap: 8px;
+  flex-wrap: wrap;
+}
+
+.mermaid-modal-controls .mermaid-toolbar-btn {
+  opacity: 1;
+}
+
+/* ========================================
+   DOCUMENT TABS & SESSION MANAGEMENT
+   ======================================== */
+
+.tab-bar {
+  display: flex;
+  align-items: center;
+  background-color: var(--header-bg);
+  border-bottom: 1px solid var(--border-color);
+  height: 32px;
+  overflow: visible;  /* ← was: overflow: hidden */
+  flex-shrink: 0;
+  padding: 0 4px;
+  gap: 0;
+  user-select: none;
+  position: relative;
+  z-index: 10;
+}
+
+.tab-list {
+  display: flex;
+  align-items: flex-end;
+  overflow-x: auto;
+  overflow-y: visible;  /* ← was: overflow-y: hidden */
+  flex: 1;
+  height: 100%;
+  scrollbar-width: none;
+  -ms-overflow-style: none;
+}
+
+.tab-list::-webkit-scrollbar {
+  display: none;
+}
+
+.tab-item {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  height: 27px;
+  padding: 0 8px 0 10px;
+  min-width: 100px;
+  max-width: 180px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  border-bottom: 1px solid transparent;
+  border-radius: 6px 6px 0 0;
+  cursor: pointer;
+  font-size: 13px;
+  color: var(--text-color);
+  white-space: nowrap;
+  /* overflow: hidden; <-- REMOVE THIS */
+  position: relative;
+  transition: background-color 0.15s ease, color 0.15s ease;
+  flex-shrink: 0;
+  margin-right: 2px;
+  opacity: 0.7;
+}
+
+.tab-item:hover {
+  background-color: var(--button-hover);
+  opacity: 0.9;
+}
+
+.tab-item.active {
+  background-color: var(--bg-color);
+  border-color: var(--border-color);
+  color: var(--accent-color);
+  border-bottom: 1px solid var(--bg-color);
+  opacity: 1;
+  z-index: 2;
+}
+
+.tab-item.unsaved::after {
+  content: '';
+  display: inline-block;
+  width: 6px;
+  height: 6px;
+  background-color: var(--accent-color);
+  border-radius: 50%;
+  flex-shrink: 0;
+  margin-left: 2px;
+}
+
+.tab-title {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  flex: 1;
+  min-width: 0;
+}
+
+.tab-close-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 16px;
+  height: 16px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 11px;
+  opacity: 0;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+}
+
+.tab-item:hover .tab-close-btn,
+.tab-item.active .tab-close-btn {
+  opacity: 0.6;
+}
+
+.tab-close-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-new-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 24px;
+  height: 24px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 16px;
+  flex-shrink: 0;
+  margin-left: 4px;
+  transition: background-color 0.15s ease, border-color 0.15s ease;
+}
+
+.tab-new-btn:hover {
+  background-color: var(--button-hover);
+  border-color: var(--border-color);
+}
+
+/* Drag-and-drop visual feedback */
+.tab-item.dragging {
+  opacity: 0.4;
+}
+
+.tab-item.drag-over {
+  border-left: 2px solid var(--accent-color);
+}
+
+/* Tab enter animation */
+@keyframes tabSlideIn {
+  from { opacity: 0; transform: translateY(4px); }
+  to   { opacity: 0.7; transform: translateY(0); }
+}
+
+.tab-item {
+  animation: tabSlideIn 0.12s ease forwards;
+}
+
+.tab-item.active {
+  animation: none;
+}
+
+/* Hide tab bar on very small screens — single-file use */
+@media (max-width: 480px) {
+  .tab-bar {
+    display: none;
+  }
+}
+
+/* ========================================
+   THREE-DOT TAB MENU
+   ======================================== */
+
+.tab-menu-btn {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 18px;
+  height: 18px;
+  border-radius: 3px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 0;
+  font-size: 14px;
+  font-weight: bold;
+  letter-spacing: 1px;
+  opacity: 0.65;
+  flex-shrink: 0;
+  transition: background-color 0.15s ease, opacity 0.15s ease;
+  position: relative;
+}
+
+.tab-item:hover .tab-menu-btn,
+.tab-item.active .tab-menu-btn {
+  opacity: 0.65;
+}
+
+.tab-menu-btn:hover {
+  background-color: var(--button-active);
+  opacity: 1 !important;
+}
+
+.tab-menu-dropdown {
+  display: none;
+  position: fixed;
+  min-width: 130px;
+  background-color: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
+  z-index: 99999;
+  overflow: hidden;
+  flex-direction: column;
+}
+
+.tab-menu-dropdown.open {
+  display: flex;
+}
+
+.tab-menu-item {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  padding: 7px 12px;
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  text-align: left;
+  transition: background-color 0.12s ease;
+  white-space: nowrap;
+}
+
+.tab-menu-item:hover {
+  background-color: var(--button-hover);
+}
+
+.tab-menu-item-danger {
+  color: var(--color-danger-fg, #d73a49);
+}
+
+.tab-menu-item-danger:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+}
+
+/* ========================================
+   RESET BUTTON
+   ======================================== */
+
+.tab-reset-btn {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  height: 24px;
+  padding: 0 8px;
+  border-radius: 5px;
+  background: none;
+  border: 1px solid var(--border-color);
+  color: var(--text-color);
+  cursor: pointer;
+  font-size: 12px;
+  flex-shrink: 0;
+  margin-left: 6px;
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
+.tab-reset-btn:hover {
+  background-color: rgba(215, 58, 73, 0.1);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: var(--color-danger-fg, #d73a49);
+}
+
+/* ========================================
+   RESET & RENAME CONFIRMATION MODALS
+   ======================================== */
+
+.reset-modal-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.45);
+  z-index: 2000;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.reset-modal-overlay.modal-overlay {
+  opacity: 0;
+  visibility: hidden;
+  transition: opacity 0.2s ease, visibility 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible {
+  opacity: 1;
+  visibility: visible;
+}
+
+.reset-modal-box {
+  background: var(--header-bg);
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 24px 28px;
+  min-width: 280px;
+  max-width: 360px;
+  box-shadow: 0 8px 32px rgba(0,0,0,0.25);
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+}
+
+.modal-box {
+  max-height: min(85vh, 760px);
+  opacity: 0;
+  transform: translateY(8px);
+  transition: transform 0.2s ease, opacity 0.2s ease;
+}
+
+.reset-modal-overlay.modal-overlay.is-visible .modal-box {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+.modal-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.modal-header .reset-modal-message {
+  text-align: left;
+  flex: 1;
+}
+
+.modal-close-btn {
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  border-radius: 6px;
+  width: 28px;
+  height: 28px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.modal-close-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.modal-body {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(60vh, 520px);
+  overflow: auto;
+  padding-right: 4px;
+}
+
+.modal-section {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.modal-section-title {
+  margin: 0;
+  font-size: 0.95rem;
+  font-weight: 600;
+}
+
+.modal-list {
+  margin: 0;
+  padding-left: 1.1rem;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  font-size: 0.85rem;
+}
+
+.modal-list a {
+  color: var(--accent-color);
+  text-decoration: none;
+}
+
+.modal-list a:hover {
+  text-decoration: underline;
+}
+
+.modal-subtext {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  line-height: 1.4;
+}
+
+.find-replace-meta {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.find-replace-nav {
+  display: inline-flex;
+  gap: 6px;
+}
+
+.find-nav-btn {
+  width: 28px;
+  height: 28px;
+  padding: 0;
+}
+
+.about-header {
+  display: flex;
+  align-items: center;
+  gap: 16px;
+  flex-wrap: wrap;
+}
+
+.about-logo {
+  width: 64px;
+  height: 64px;
+  border-radius: 12px;
+  border: 1px solid var(--border-color);
+  object-fit: cover;
+}
+
+.about-details {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.about-title {
+  margin: 0;
+  font-size: 1.05rem;
+  font-weight: 600;
+}
+
+.about-description {
+  margin: 0;
+  font-size: 0.85rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.about-meta {
+  margin: 0;
+  font-size: 0.78rem;
+  color: var(--text-secondary, #57606a);
+}
+
+.modal-body kbd {
+  padding: 2px 6px;
+  border-radius: 4px;
+  background-color: var(--button-bg);
+  border: 1px solid var(--border-color);
+  font-size: 0.75rem;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+}
+
+.reset-modal-box--wide {
+  width: min(92vw, 640px);
+  max-width: 640px;
+}
+
+.reset-modal-message {
+  margin: 0;
+  font-size: 14px;
+  color: var(--text-color);
+  font-weight: 500;
+  text-align: center;
+}
+
+.reset-modal-actions {
+  display: flex;
+  gap: 10px;
+  justify-content: flex-end;
+}
+
+.reset-modal-btn {
+  padding: 6px 16px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--button-bg);
+  color: var(--text-color);
+  font-size: 13px;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.reset-modal-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.reset-modal-confirm {
+  background-color: var(--color-danger-fg, #d73a49);
+  border-color: var(--color-danger-fg, #d73a49);
+  color: #fff;
+}
+
+.reset-modal-confirm:hover {
+  background-color: #b02a37;
+  border-color: #b02a37;
+}
+
+/* ========================================
+   RESET MODAL FORM FIELDS
+   ======================================== */
+
+.reset-modal-field {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  text-align: left;
+}
+
+.reset-modal-field-group {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.reset-modal-label {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  font-weight: 600;
+}
+
+.reset-modal-toggle-group {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.reset-modal-option {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 13px;
+  color: var(--text-color);
+}
+
+.reset-modal-option input {
+  margin: 0;
+}
+
+/* ========================================
+   RENAME MODAL INPUT
+   ======================================== */
+
+.rename-modal-input {
+  width: 100%;
+  padding: 7px 10px;
+  border-radius: 6px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  color: var(--text-color);
+  font-size: 13px;
+  outline: none;
+  box-sizing: border-box;
+}
+
+.rename-modal-input:focus {
+  border-color: var(--accent-color);
+}
+
+/* ========================================
+   TOOLBAR POPUP PANELS
+   ======================================== */
+
+.reset-modal-box--xl {
+  width: min(94vw, 980px);
+  max-width: 980px;
+}
+
+.modal-empty {
+  margin: 0;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
+  gap: 12px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px;
+}
+
+.symbol-grid {
+  display: flex;
+  flex-direction: column;
+  gap: 16px;
+  max-height: min(52vh, 440px);
+  overflow: auto;
+  padding: 4px 2px;
+}
+
+.symbol-section-title {
+  margin: 0;
+  font-size: 11px;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--text-secondary, #57606a);
+}
+
+.symbol-section-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+  gap: 12px;
+}
+
+.alert-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
+  gap: 12px;
+  max-height: min(45vh, 360px);
+  overflow: auto;
+  padding: 2px;
+}
+
+.emoji-item,
+.symbol-item,
+.alert-option {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  align-items: center;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 10px;
+  background: var(--bg-color);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: border-color 0.2s ease, box-shadow 0.2s ease, background-color 0.2s ease;
+}
+
+.emoji-item:focus-visible,
+.symbol-item:focus-visible,
+.alert-option:focus-visible {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 2px;
+}
+
+.emoji-item.is-selected,
+.symbol-item.is-selected,
+.alert-option.is-selected {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
+  background-color: rgba(88, 166, 255, 0.08);
+}
+
+.emoji-preview {
+  width: 36px;
+  height: 36px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.emoji-preview img {
+  width: 32px;
+  height: 32px;
+}
+
+.emoji-shortcode {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+  text-align: center;
+}
+
+.emoji-copy-btn,
+.symbol-copy-btn {
+  border: none;
+  background: transparent;
+  color: var(--text-secondary, #57606a);
+  cursor: pointer;
+  padding: 2px;
+  border-radius: 4px;
+}
+
+.emoji-copy-btn:hover,
+.symbol-copy-btn:hover {
+  color: var(--text-color);
+  background: var(--button-hover);
+}
+
+.emoji-copy-btn.is-copied,
+.symbol-copy-btn.is-copied {
+  color: var(--accent-color);
+}
+
+.symbol-preview {
+  font-size: 28px;
+  line-height: 1;
+}
+
+.symbol-code {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.alert-option {
+  align-items: stretch;
+  text-align: left;
+  padding: 12px;
+}
+
+.alert-preview {
+  margin: 0;
+}
+
+.alert-preview .markdown-alert {
+  padding: 0.5rem 0.9rem;
+  border-left: 0.25em solid;
+  border-radius: 0.375rem;
+}
+
+.alert-preview .markdown-alert-title {
+  margin: 0 0 6px;
+  font-weight: 600;
+  line-height: 1.25;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.alert-preview .markdown-alert-icon {
+  display: inline-flex;
+  width: 16px;
+  height: 16px;
+}
+
+.alert-preview .markdown-alert-icon svg {
+  width: 16px;
+  height: 16px;
+  fill: currentColor;
+}
+
+.alert-preview .markdown-alert > *:not(.markdown-alert-title) {
+  color: var(--text-color);
+}
+
+.alert-preview .markdown-alert-note {
+  color: #0969da;
+  border-left-color: #0969da;
+  background-color: #ddf4ff;
+}
+
+.alert-preview .markdown-alert-tip {
+  color: #1a7f37;
+  border-left-color: #1a7f37;
+  background-color: #dafbe1;
+}
+
+.alert-preview .markdown-alert-important {
+  color: #8250df;
+  border-left-color: #8250df;
+  background-color: #fbefff;
+}
+
+.alert-preview .markdown-alert-warning {
+  color: #9a6700;
+  border-left-color: #9a6700;
+  background-color: #fff8c5;
+}
+
+.alert-preview .markdown-alert-caution {
+  color: #cf222e;
+  border-left-color: #cf222e;
+  background-color: #ffebe9;
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-note {
+  color: #4493f8;
+  border-left-color: #4493f8;
+  background-color: rgba(31, 111, 235, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-tip {
+  color: #3fb950;
+  border-left-color: #3fb950;
+  background-color: rgba(35, 134, 54, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-important {
+  color: #ab7df8;
+  border-left-color: #ab7df8;
+  background-color: rgba(137, 87, 229, 0.15);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-warning {
+  color: #d29922;
+  border-left-color: #d29922;
+  background-color: rgba(210, 153, 34, 0.18);
+}
+
+[data-theme="dark"] .alert-preview .markdown-alert-caution {
+  color: #f85149;
+  border-left-color: #f85149;
+  background-color: rgba(248, 81, 73, 0.18);
+}
+
+.github-import-error {
+  margin: 0;
+  font-size: 12px;
+  color: var(--color-danger-fg, #d73a49);
+  text-align: left;
+  line-height: 1.5;
+}
+
+.github-import-error.is-info {
+  color: var(--text-secondary, #57606a);
+}
+
+#github-import-modal .reset-modal-box {
+  width: 60vw;
+  max-width: 60vw;
+  min-width: 340px;
+  padding: 30px 34px;
+  gap: 16px;
+  box-shadow: 0 20px 48px rgba(0, 0, 0, 0.22);
+}
+
+#github-import-modal .reset-modal-message {
+  font-size: 18px;
+  line-height: 1.35;
+  text-align: left;
+}
+
+#github-import-url,
+#github-import-file-select {
+  min-height: 46px;
+  padding: 10px 12px;
+  font-size: 15px;
+}
+
+#github-import-file-select {
+  min-height: 180px;
+}
+
+.github-import-tree {
+  max-height: 420px;
+  overflow: auto;
+  border: 1px solid var(--border-color);
+  border-radius: 10px;
+  padding: 12px;
+  background: var(--bg-color);
+}
+
+.github-import-selection-toolbar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  padding: 10px 12px;
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  background: var(--button-bg);
+}
+
+.github-import-selected-count {
+  font-size: 14px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.github-import-tree ul {
+  list-style: none;
+  margin: 0;
+  padding-left: 18px;
+}
+
+.github-import-tree > ul {
+  padding-left: 4px;
+}
+
+.github-import-tree li {
+  margin: 2px 0;
+}
+
+.github-tree-folder-label {
+  display: inline-block;
+  font-size: 14px;
+  color: var(--text-secondary, #57606a);
+  margin-bottom: 4px;
+}
+
+.github-tree-file-btn {
+  border: 0;
+  background: transparent;
+  color: var(--text-color);
+  cursor: pointer;
+  padding: 6px 8px;
+  border-radius: 6px;
+  text-align: left;
+  width: 100%;
+  font-size: 14px;
+}
+
+.github-tree-file-btn:hover,
+.github-tree-file-btn:focus-visible {
+  background: var(--button-hover);
+  outline: none;
+}
+
+.github-tree-file-btn.is-selected {
+  background: rgba(56, 139, 253, 0.14);
+  color: var(--accent-color);
+}
+
+#github-import-modal .reset-modal-actions {
+  gap: 12px;
+}
+
+#github-import-modal .reset-modal-btn {
+  min-height: 42px;
+  padding: 9px 18px;
+  font-size: 14px;
+}
+
+@media (max-width: 576px) {
+  #github-import-modal .reset-modal-box {
+    width: 95vw;
+    max-width: 95vw;
+    min-width: 0;
+    padding: 20px;
+    gap: 14px;
+  }
+
+  .github-import-selection-toolbar {
+    flex-direction: column;
+    align-items: stretch;
+  }
+
+  #github-import-modal .reset-modal-message {
+    font-size: 16px;
+  }
+
+  #github-import-modal .reset-modal-actions {
+    flex-direction: column-reverse;
+  }
+
+  #github-import-modal .reset-modal-btn {
+    width: 100%;
+  }
+}
+
+.frontmatter-table {
+  border-collapse: collapse;
+  margin-bottom: 1.5em;
+  font-size: 0.9em;
+  width: auto;
+  max-width: 100%;
+}
+
+.frontmatter-table th,
+.frontmatter-table td {
+  border: 1px solid var(--border-color);
+  padding: 6px 13px;
+  vertical-align: top;
+  color: var(--text-color);
+}
+
+.frontmatter-table tr:nth-child(odd) th,
+.frontmatter-table tr:nth-child(odd) td {
+  background-color: var(--table-bg);
+}
+
+.frontmatter-table tr:nth-child(even) th,
+.frontmatter-table tr:nth-child(even) td {
+  background-color: var(--editor-bg);
+}
+
+.frontmatter-table th {
+  font-weight: 600;
+  text-align: right;
+  white-space: nowrap;
+  vertical-align: middle;
+}
+
+.frontmatter-table td {
+  text-align: left;
+}
+
+.fm-complex {
+  margin: 0;
+  padding: 4px 6px;
+  font-size: 0.8em;
+  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  white-space: pre-wrap;
+  word-break: break-word;
+  background: transparent;
+  border: none;
+  color: var(--text-color);
+}
+
+.fm-tag {
+  display: inline-block;
+  padding: 2px 8px;
+  margin: 2px 3px 2px 0;
+  border: 1px solid var(--border-color);
+  border-radius: 2em;
+  font-size: 0.8em;
+  font-weight: 500;
+  color: var(--accent-color);
+  background-color: var(--button-bg);
+  white-space: nowrap;
+}
+
+/* ========================================
+   RTL SUPPORT
+   ======================================== */
+
+[dir="rtl"] body {
+  direction: rtl;
+}
+
+[dir="rtl"] .editor-pane {
+  padding-left: 0px;
+  padding-right: 20px;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor,
+[dir="rtl"] .markdown-body {
+  direction: rtl;
+  text-align: right;
+}
+
+[dir="rtl"] .markdown-body pre,
+[dir="rtl"] .markdown-body code,
+[dir="rtl"] .fm-complex {
+  direction: ltr;
+  text-align: left;
+}
+
+[dir="rtl"] .line-numbers {
+  left: auto;
+  right: 20px;
+  padding: 10px 0 10px 8px;
+  text-align: left;
+  border-right: none;
+  border-left: 1px solid var(--border-color);
+}
+
+[dir="rtl"] #markdown-editor {
+  padding-left: 10px;
+  padding-right: calc(10px + var(--line-number-gutter));
+}
+
+[dir="rtl"] .editor-highlight-layer {
+  inset: 20px calc(20px + var(--line-number-gutter)) 20px 0;
+}
+
+[dir="rtl"] .mobile-menu-item,
+[dir="rtl"] .tab-menu-item,
+[dir="rtl"] .modal-header .reset-modal-message,
+[dir="rtl"] .reset-modal-field,
+[dir="rtl"] .alert-option,
+[dir="rtl"] .github-import-error,
+[dir="rtl"] #github-import-modal .reset-modal-message,
+[dir="rtl"] .github-tree-file-btn,
+[dir="rtl"] .frontmatter-table td {
+  text-align: right;
+}
+
+[dir="rtl"] .github-import-tree ul {
+  padding-left: 0;
+  padding-right: 18px;
+}
+
+[dir="rtl"] .github-import-tree > ul {
+  padding-right: 4px;
+}
+
+[dir="rtl"] .markdown-body .markdown-alert,
+[dir="rtl"] .alert-preview .markdown-alert {
+  border-left: 0;
+  border-right: 0.25em solid currentColor;
+}
+
+/* ============================================
+   SHARE MODAL
+   ============================================ */
+
+.share-modal-description {
+  font-size: 13px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+}
+
+.share-mode-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.share-mode-card {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 12px 14px;
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  background: var(--bg-color);
+  cursor: pointer;
+  transition: border-color 0.15s ease, background-color 0.15s ease;
+  user-select: none;
+}
+
+.share-mode-card:hover {
+  border-color: var(--accent-color);
+  background: var(--button-hover);
+}
+
+.share-mode-card.is-selected {
+  border-color: var(--accent-color);
+  background: color-mix(in srgb, var(--accent-color) 8%, transparent);
+}
+
+.share-mode-card input[type="radio"] {
+  display: none;
+}
+
+.share-card-icon {
+  font-size: 18px;
+  width: 28px;
+  text-align: center;
+  color: var(--text-secondary, #57606a);
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-icon {
+  color: var(--accent-color);
+}
+
+.share-card-body {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  flex: 1;
+  min-width: 0;
+}
+
+.share-card-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.share-card-desc {
+  font-size: 12px;
+  color: var(--text-secondary, #57606a);
+}
+
+.share-card-check {
+  width: 18px;
+  text-align: center;
+  color: var(--accent-color);
+  opacity: 0;
+  transition: opacity 0.15s ease;
+  flex-shrink: 0;
+}
+
+.share-mode-card.is-selected .share-card-check {
+  opacity: 1;
+}
+
+.share-url-row {
+  display: flex;
+  gap: 8px;
+  align-items: center;
+}
+
+.share-url-input {
+  flex: 1;
+  font-size: 12px;
+  font-family: var(--font-mono, monospace);
+  color: var(--text-secondary, #57606a);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.share-copy-btn {
+  flex-shrink: 0;
+  padding: 6px 10px;
+}
+
+.share-copy-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.share-modal-notice {
+  font-size: 11px;
+  color: var(--text-secondary, #57606a);
+  margin: 0;
+  display: flex;
+  align-items: center;
+  gap: 5px;
+}
+
+/* ==========================================================================
+   Multilingual & CJK Optimization styles added by Aegis SEO agency
+   ========================================================================== */
+.lang-select-item {
+  display: flex !important;
+  align-items: center;
+  gap: 8px;
+  cursor: pointer;
+  transition: background-color 0.2s ease, padding-left 0.2s ease;
+}
+
+.lang-select-item:hover {
+  padding-left: 12px;
+}
+
+.lang-select-item.active {
+  background-color: var(--accent-color) !important;
+  color: #ffffff !important;
+  font-weight: 600;
+}
+
+/* Adjust CJK text layout for maximum readability inside the preview pane */
+html[lang="zh"] .markdown-body,
+html[lang="ja"] .markdown-body,
+html[lang="ko"] .markdown-body {
+  line-height: 1.75 !important;
+  letter-spacing: 0.03em;
+  word-break: keep-all;
+  overflow-wrap: break-word;
+  text-align: justify;
+}
+
+/* Specific heading spacing improvements for CJK characters */
+html[lang="zh"] .markdown-body h1, html[lang="zh"] .markdown-body h2, html[lang="zh"] .markdown-body h3,
+html[lang="ja"] .markdown-body h1, html[lang="ja"] .markdown-body h2, html[lang="ja"] .markdown-body h3,
+html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang="ko"] .markdown-body h3 {
+  font-weight: 700;
+  letter-spacing: 0.02em;
+  margin-top: 1.4em;
+  margin-bottom: 0.6em;
+}
+
+/* Smooth fade and scale transition for dropdown active states */
+.dropdown-menu {
+  opacity: 0;
+  transform: translateY(8px) scale(0.98);
+  display: block;
+  visibility: hidden;
+  transition: opacity 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.2s;
+}
+
+.dropdown-menu.show {
+  opacity: 1;
+  transform: translateY(0) scale(1);
+  visibility: visible;
+}
+
+/* ========================================
+   FIND & REPLACE FLOATING PANEL DESIGN
+   ======================================== */
+:root {
+  --fr-bg: rgba(255, 255, 255, 0.95);
+  --fr-border: #d0d7de;
+  --fr-shadow: 0 8px 24px rgba(140, 149, 159, 0.2);
+  --fr-btn-active: #0969da;
+  --fr-btn-active-bg: #ddf4ff;
+  --fr-match-highlight: #ffdf5d;
+  --fr-match-active: #ff9b30;
+  --fr-error-bg: #ffebe9;
+  --fr-error-border: #ff8577;
+  --fr-text-danger: #cf222e;
+}
+
+[data-theme="dark"] {
+  --fr-bg: rgba(28, 33, 40, 0.98);
+  --fr-border: #444c56;
+  --fr-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
+  --fr-btn-active: #2f81f7;
+  --fr-btn-active-bg: rgba(56, 139, 253, 0.15);
+  --fr-match-highlight: rgba(187, 128, 9, 0.4);
+  --fr-match-active: #f1e05a;
+  --fr-error-bg: rgba(248, 81, 73, 0.1);
+  --fr-error-border: rgba(248, 81, 73, 0.4);
+  --fr-text-danger: #ff7b72;
+}
+
+.find-replace-panel {
+  position: fixed;
+  top: 100px;
+  right: 20px;
+  width: 340px;
+  background-color: var(--fr-bg);
+  border: 1px solid var(--fr-border);
+  border-radius: 12px;
+  box-shadow: var(--fr-shadow);
+  z-index: 1050;
+  display: flex;
+  flex-direction: column;
+  backdrop-filter: blur(10px);
+  -webkit-backdrop-filter: blur(10px);
+  transition: opacity 0.2s ease, transform 0.2s ease;
+  user-select: none;
+  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+}
+
+.find-replace-panel.docked {
+  position: relative;
+  top: 0 !important;
+  right: 0 !important;
+  height: 100%;
+  border-radius: 0;
+  border-top: none;
+  border-bottom: none;
+  border-right: none;
+  border-left: 1px solid var(--fr-border);
+  box-shadow: none;
+  backdrop-filter: none;
+  z-index: 10;
+  flex-shrink: 0;
+}
+
+.find-replace-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 8px 12px;
+  border-bottom: 1px solid var(--fr-border);
+  cursor: move;
+  background-color: var(--header-bg);
+  border-top-left-radius: 11px;
+  border-top-right-radius: 11px;
+}
+
+.find-replace-panel.docked .find-replace-header {
+  cursor: default;
+  border-top-left-radius: 0;
+  border-top-right-radius: 0;
+}
+
+.find-replace-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-color);
+}
+
+.find-replace-header-actions {
+  display: flex;
+  gap: 4px;
+}
+
+.panel-icon-btn {
+  background: none;
+  border: none;
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 6px;
+  border-radius: 4px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: background-color 0.15s ease;
+}
+
+.panel-icon-btn:hover {
+  background-color: var(--button-hover);
+}
+
+.find-replace-body {
+  padding: 12px;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.find-replace-field-row {
+  display: flex;
+  flex-direction: column;
+  position: relative;
+}
+
+.find-input-container, .replace-input-container {
+  display: flex;
+  align-items: center;
+  border: 1px solid var(--fr-border);
+  border-radius: 6px;
+  background-color: var(--bg-color);
+  padding: 2px 4px;
+  width: 100%;
+}
+
+.find-input-container:focus-within, .replace-input-container:focus-within {
+  border-color: var(--accent-color);
+  box-shadow: 0 0 0 3px rgba(9, 105, 218, 0.15);
+}
+
+.find-input-field {
+  flex: 1;
+  border: none;
+  background: transparent;
+  color: var(--text-color);
+  font-size: 13px;
+  padding: 4px 6px;
+  outline: none;
+  width: 50%;
+}
+
+.find-options-group {
+  display: flex;
+  gap: 2px;
+}
+
+.find-option-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 11px;
+  font-weight: 600;
+  cursor: pointer;
+  padding: 2px 5px;
+  border-radius: 4px;
+  transition: background-color 0.12s ease, color 0.12s ease;
+  min-width: 22px;
+  height: 22px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.find-option-btn:hover {
+  background-color: var(--button-hover);
+  color: var(--text-color);
+}
+
+.find-option-btn.active {
+  background-color: var(--fr-btn-active-bg);
+  color: var(--fr-btn-active);
+}
+
+.find-error-drawer {
+  background-color: var(--fr-error-bg);
+  border: 1px solid var(--fr-error-border);
+  border-radius: 6px;
+  padding: 6px 10px;
+  font-size: 11px;
+  color: var(--fr-text-danger);
+  line-height: 1.3;
+}
+
+.find-replace-meta-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 2px 4px;
+}
+
+.find-match-count {
+  font-size: 12px;
+  color: var(--text-secondary);
+}
+
+.find-nav-group {
+  display: flex;
+  gap: 4px;
+}
+
+.find-nav-arrow-btn {
+  background: none;
+  border: 1px solid var(--fr-border);
+  color: var(--text-color);
+  font-size: 12px;
+  cursor: pointer;
+  padding: 2px 8px;
+  border-radius: 4px;
+  transition: background-color 0.15s ease;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.find-nav-arrow-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.find-nav-arrow-btn:disabled {
+  opacity: 0.4;
+  cursor: not-allowed;
+}
+
+.find-drawer-toggle-row {
+  border-top: 1px solid var(--fr-border);
+  margin-top: 4px;
+  padding-top: 6px;
+}
+
+.drawer-toggle-btn {
+  background: none;
+  border: none;
+  color: var(--text-secondary);
+  font-size: 12px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  padding: 2px 4px;
+  border-radius: 4px;
+  transition: color 0.15s ease;
+}
+
+.drawer-toggle-btn:hover {
+  color: var(--text-color);
+}
+
+.find-replace-drawer-content {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 4px 6px;
+  border-top: 1px dashed var(--fr-border);
+  margin-top: 2px;
+  padding-top: 8px;
+}
+
+.drawer-field {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.drawer-field.check-field {
+  flex-direction: row;
+  align-items: center;
+  gap: 6px;
+  padding: 2px 0;
+}
+
+.drawer-label {
+  font-size: 11px;
+  font-weight: 600;
+  color: var(--text-secondary);
+}
+
+.drawer-select {
+  width: 100%;
+  padding: 4px 6px;
+  border-radius: 4px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--bg-color);
+  color: var(--text-color);
+  font-size: 12px;
+  outline: none;
+}
+
+.drawer-checkbox {
+  margin: 0;
+  cursor: pointer;
+}
+
+.drawer-label-checkbox {
+  font-size: 12px;
+  color: var(--text-color);
+  cursor: pointer;
+}
+
+.find-replace-actions-footer {
+  display: flex;
+  gap: 6px;
+  padding: 8px 12px 12px 12px;
+  border-top: 1px solid var(--fr-border);
+  background-color: var(--header-bg);
+  border-bottom-left-radius: 11px;
+  border-bottom-right-radius: 11px;
+}
+
+.find-replace-panel.docked .find-replace-actions-footer {
+  border-bottom-left-radius: 0;
+  border-bottom-right-radius: 0;
+}
+
+.fr-action-btn {
+  flex: 1;
+  padding: 6px 8px;
+  font-size: 12px;
+  font-weight: 500;
+  border-radius: 6px;
+  border: 1px solid var(--fr-border);
+  background-color: var(--button-bg);
+  color: var(--text-color);
+  cursor: pointer;
+  transition: background-color 0.15s ease, border-color 0.15s ease;
+  text-align: center;
+}
+
+.fr-action-btn:hover:not(:disabled) {
+  background-color: var(--button-hover);
+}
+
+.fr-action-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.fr-action-btn.secondary {
+  max-width: 60px;
+}
+
+/* ========================================
+   DIFF PREVIEW CONTAINER
+   ======================================== */
+.diff-preview-body {
+  padding: 16px;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.diff-container {
+  border: 1px solid var(--fr-border);
+  border-radius: 8px;
+  background-color: var(--bg-color);
+  max-height: 400px;
+  overflow: auto;
+  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
+  font-size: 12px;
+  line-height: 1.5;
+}
+
+.diff-line {
+  display: flex;
+  padding: 1px 8px;
+}
+
+.diff-line.addition {
+  background-color: rgba(46, 160, 67, 0.15);
+  color: #3fb950;
+}
+
+.diff-line.deletion {
+  background-color: rgba(248, 81, 73, 0.15);
+  color: #f85149;
+}
+
+.diff-line.context {
+  color: var(--text-secondary);
+}
+
+.diff-line-num {
+  width: 40px;
+  flex-shrink: 0;
+  text-align: right;
+  padding-right: 12px;
+  border-right: 1px solid var(--fr-border);
+  user-select: none;
+  opacity: 0.5;
+}
+
+.diff-line-content {
+  padding-left: 12px;
+  white-space: pre-wrap;
+  word-break: break-all;
+}
+
+/* ========================================
+   DOCK LAYOUT CODES
+   ======================================== */
+.content-container {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-dock-wrapper {
+  display: flex;
+  flex: 1;
+  overflow: hidden;
+  position: relative;
+}
+
+.editor-pane-inner {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  position: relative;
+  overflow: hidden;
+}
\ No newline at end of file