diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..753bd53
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,37 @@
+name: CI
+
+on:
+  push:
+    branches: [main, dev]
+  pull_request:
+    branches: [main, dev]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        python-version: ["3.11", "3.12"]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: "pip"
+
+      - name: Install dependencies
+        run: pip install -e ".[dev]"
+
+      - name: Lint with ruff
+        run: ruff check .
+
+      - name: Check formatting
+        run: ruff format --check .
+
+      - name: Run tests with coverage
+        run: pytest --cov=mathlib --cov-report=term-missing
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index b7faf40..672bc0f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -205,3 +205,7 @@ cython_debug/
 marimo/_static/
 marimo/_lsp/
 __marimo__/
+
+
+# VsCode settings
+.vscode/
\ No newline at end of file
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..303bfd6
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,7 @@
+{
+    "python.defaultInterpreterPath": ".venv/Scripts/python",
+    "editor.formatOnSave": true,
+    "[python]": {
+        "editor.defaultFormatter": "charliermarsh.ruff"
+    }
+}
\ No newline at end of file
diff --git a/pymath/__init__.py b/pymath/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pymath/arithmetic.py b/pymath/arithmetic.py
new file mode 100644
index 0000000..e69de29
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..36e2d69
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,28 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "etuptools.build_meta"
+
+[project]
+name = "mathlib"
+version = "0.1.0"
+description = "A math library built for learning"
+requires-python = ">=3.11"
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.0",
+    "pytest-cov",   # coverage reports
+    "ruff",         # linting + formatting (replaces flake8+black)
+]
+
+[tool.ruff]
+line-length = 88
+
+[tool.ruff.lint]
+select = ["E", "F", "W"]   # pycodestyle + pyflakes rules
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+
+[tool.coverage.report]
+omit = ["tests/*"]
diff --git a/setup b/setup
new file mode 100644
index 0000000..9558f00
--- /dev/null
+++ b/setup
@@ -0,0 +1,27 @@
+# Create venv (do this once per machine)
+python -m venv .venv
+
+# Activate — Linux/Mac
+source .venv/bin/activate
+
+# Activate — Windows (VSCode terminal)
+.venv\Scripts\activate
+
+# Install the project in editable mode + dev tools
+pip install -e ".[dev]"
+```
+
+The `-e` flag means **editable install** — changes to your `mathlib/` code take effect immediately without reinstalling.
+
+---
+
+### 4. `.gitignore`
+```
+.venv/
+__pycache__/
+*.pyc
+.coverage
+htmlcov/
+dist/
+*.egg-info/
+.vscode/
\ No newline at end of file
diff --git a/test/__init__.py b/test/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/test/test_arithmetic.py b/test/test_arithmetic.py
new file mode 100644
index 0000000..e69de29