Fun_With_Math/experiments/basic/primes.html at main · SimiaCryptus/Fun_With_Math · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <meta name="description" content="Watch the Sieve of Eratosthenes find primes interactively." />
  <title>Prime Number Sieve – Fun With Math</title>
  <link rel="stylesheet" href="../../css/style.css" />
  <style>
    #grid {
      display: grid;
      gap: 3px;
      padding: 1rem;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius);
      overflow: auto;
    }
    .cell {
      width: 100%;
      aspect-ratio: 1;
      border-radius: 4px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: clamp(.5rem, 1.4vw, .75rem);
      font-weight: 600;
      font-family: 'Fira Code', Consolas, monospace;
      background: rgba(255,255,255,.05);
      color: var(--text-muted);
      transition: background .25s, color .25s, transform .15s;
      cursor: default;
    }
    .cell.eliminated {
      background: rgba(255,255,255,.03);
      color: rgba(255,255,255,.12);
      text-decoration: line-through;
    }
    .cell.prime {
      background: rgba(88,166,255,.2);
      color: var(--accent);
      transform: scale(1.08);
    }
    .cell.current-factor {
      background: rgba(188,140,255,.35);
      color: var(--accent2);
      transform: scale(1.15);
    }
    #statsBar {
      display: flex;
      gap: 1.5rem;
      flex-wrap: wrap;
      font-size: .85rem;
      color: var(--text-muted);
      padding: .5rem 0;
    }
    #statsBar strong { color: var(--text); }
    #primeList {
      font-family: 'Fira Code', Consolas, monospace;
      font-size: .8rem;
      color: var(--accent);
      word-break: break-all;
      line-height: 1.9;
      max-height: 160px;
      overflow-y: auto;
      padding: .5rem;
      background: var(--bg);
      border: 1px solid var(--border);
      border-radius: 6px;
    }
  </style>
</head>
<body>

<nav>
  <a class="brand" href="../../index.html">∑ Fun With Math</a>
  <a href="../../index.html">← All Experiments</a>
</nav>

<div class="page-header">
  <h1>Prime Number Sieve</h1>
  <p>Watch the Sieve of Eratosthenes eliminate composites in real time.</p>
</div>

<div class="experiment-layout">
  <div>
    <div id="statsBar">
      <span>Primes found: <strong id="primeCount">—</strong></span>
      <span>Current factor: <strong id="currentFactor">—</strong></span>
      <span>Step: <strong id="stepDisplay">—</strong></span>
    </div>
    <div id="grid"></div>
  </div>

  <aside class="controls">
    <h3>Controls</h3>

    <label>
      Limit (n): <span id="limitLabel">200</span>
      <input type="range" id="limitRange" min="20" max="400" step="10" value="200" />
    </label>

    <label>
      Animation Speed
      <select id="speed">
        <option value="600">Slow</option>
        <option value="250" selected>Medium</option>
        <option value="80">Fast</option>
        <option value="20">Very Fast</option>
      </select>
    </label>

    <div style="display:flex;gap:.5rem;flex-wrap:wrap">
      <button class="btn btn-primary"   id="startBtn">▶ Start</button>
      <button class="btn btn-secondary" id="resetBtn">↺ Reset</button>
    </div>

    <div class="info-box">
      <h4>Primes</h4>
      <div id="primeList">—</div>
    </div>

    <div class="info-box">
      <h4>Algorithm</h4>
      <ol style="padding-left:1.2rem;line-height:2">
        <li>List integers 2 … n</li>
        <li>Mark 2 as prime; cross out multiples</li>
        <li>Find next unmarked number; repeat</li>
        <li>All remaining numbers are prime</li>
      </ol>
    </div>
  </aside>
</div>

<footer>
  <p><a href="../../index.html">← Back to all experiments</a></p>
</footer>

<script>
(function () {
  const grid          = document.getElementById('grid');
  const limitRange    = document.getElementById('limitRange');
  const limitLabel    = document.getElementById('limitLabel');
  const speedSelect   = document.getElementById('speed');
  const startBtn      = document.getElementById('startBtn');
  const resetBtn      = document.getElementById('resetBtn');
  const primeCountEl  = document.getElementById('primeCount');
  const currentFactEl = document.getElementById('currentFactor');
  const stepEl        = document.getElementById('stepDisplay');
  const primeListEl   = document.getElementById('primeList');

  let n = 200;
  let sieve = [];       // false = still candidate, true = eliminated
  let cells = [];
  let animTimer = null;
  let running = false;

  // ── Build grid ───────────────────────────────────────────
  function buildGrid() {
    n = parseInt(limitRange.value);
    sieve = new Array(n + 1).fill(false);
    sieve[0] = sieve[1] = true; // not prime

    // Determine columns for a roughly-square grid
    const cols = Math.ceil(Math.sqrt(n));
    grid.style.gridTemplateColumns = `repeat(${cols}, 1fr)`;

    grid.innerHTML = '';
    cells = [null, null]; // index 0 and 1 unused
    for (let i = 2; i <= n; i++) {
      const div = document.createElement('div');
      div.className = 'cell';
      div.textContent = i;
      div.title = `${i}`;
      grid.appendChild(div);
      cells.push(div);
    }
    updateStats(null, 0);
    primeListEl.textContent = '—';
  }

  function updateStats(factor, step) {
    const primes = [];
    for (let i = 2; i <= n; i++) {
      if (!sieve[i]) primes.push(i);
    }
    primeCountEl.textContent = primes.length;
    currentFactEl.textContent = factor !== null ? factor : '—';
    stepEl.textContent = step > 0 ? step : '—';
    if (primes.length > 0) {
      primeListEl.textContent = primes.join('  ');
    }
    return primes;
  }

  // ── Animation generator ──────────────────────────────────
  function* sieveGenerator() {
    let step = 0;
    for (let p = 2; p * p <= n; p++) {
      if (sieve[p]) continue;

      // Highlight current prime
      cells[p].classList.add('current-factor');
      yield { factor: p, step: ++step, phase: 'factor' };

      // Eliminate multiples
      for (let m = p * p; m <= n; m += p) {
        if (!sieve[m]) {
          sieve[m] = true;
          cells[m].classList.add('eliminated');
          cells[m].classList.remove('prime');
          yield { factor: p, step: ++step, phase: 'eliminate', target: m };
        }
      }

      // Mark p as confirmed prime
      cells[p].classList.remove('current-factor');
      cells[p].classList.add('prime');
    }

    // Mark all remaining candidates as prime
    for (let i = 2; i <= n; i++) {
      if (!sieve[i]) cells[i].classList.add('prime');
    }
    yield { factor: null, step: ++step, phase: 'done' };
  }

  function startAnimation() {
    if (running) return;
    running = true;
    startBtn.disabled = true;
    resetBtn.disabled = true;

    const gen = sieveGenerator();

    function tick() {
      const { value, done } = gen.next();
      if (done || (value && value.phase === 'done')) {
        updateStats(null, value ? value.step : 0);
        running = false;
        startBtn.disabled = false;
        resetBtn.disabled = false;
        return;
      }
      updateStats(value.factor, value.step);
      animTimer = setTimeout(tick, parseInt(speedSelect.value));
    }
    tick();
  }

  function resetAll() {
    if (animTimer) clearTimeout(animTimer);
    running = false;
    startBtn.disabled = false;
    resetBtn.disabled = false;
    buildGrid();
  }

  // ── Event listeners ──────────────────────────────────────
  limitRange.addEventListener('input', () => {
    limitLabel.textContent = limitRange.value;
    if (!running) buildGrid();
  });
  startBtn.addEventListener('click', startAnimation);
  resetBtn.addEventListener('click', resetAll);

  // ── Init ─────────────────────────────────────────────────
  buildGrid();
})();
</script>
</body>
</html>