Computer Aided Geometry (CAG)

Browser-based compass-and-straightedge construction tool for drawing geometric constructions with infinite lines, full circles, inked boundaries, and flood-filled regions.

Live app: https://emh.io/cag

What It Does

• Draw infinite construction lines and full circles.
• Snap to intersections and nearby geometry for precise placement.
• Ink segments/arcs between intersections to define boundaries.
• Fill enclosed regions with color.
• Pan, zoom, undo/redo, and delete geometry with dependency cleanup.
• Copy and paste a geometric measure distance.

Controls

• 1 Compass
• 2 Straightedge
• 3 Ink
• 4 Fill
• 5 Copy Measure
• 6 Paste Measure
• 7 Select
• Z Undo
• Y Redo
• X Clear all
• 0 Reset view
• Space + drag to pan (or middle-mouse drag)
• Mouse wheel to zoom

Local Development

This project is plain HTML/CSS/JS and runs directly in the browser.

1. Clone the repo.
2. Open index.html in a browser, or serve the folder with any static file server.

Example:

python3 -m http.server 8080

Then open http://localhost:8080.

Tech

• JavaScript
• Preact + Signals
• Full-screen HTML canvas

License

MIT. See LICENSE.