GeometryForge

Geometry is something you build. Make angles, raise polygons, slide and flip shapes across a grid, and stretch a band to an exact area — then meet the guides who each embody one geometric idea.

Level 1

For grown-ups — progress report →A private, on-device snapshot mapped to the skill areas practiced. Export a CSV or print — nothing leaves this device.

Build & reason — hands-on geometry surfaces

Six ways to do geometry, rebuilt for the browser — the same skills as the iOS app, plus two you can only do here.

Construction Lab ✨ new Compass and straightedge, exactly — build an equilateral triangle, a perpendicular bisector, a midpoint, a perpendicular through a point. An exact engine checks your construction and scores your move economy. Property-Chain Reasoning ✨ new Build a proof yourself: pick the deduction that follows next — vertical angles, triangle sums, parallel lines, exterior angles — until you reach the conclusion. Every wrong pick explains why. Fill the Point ✨ new Discover which shapes tile: place polygon corners into a vertex and watch them fill toward exactly 360° — no gap, no overlap. Six triangles? Three hexagons? A square and two octagons? Geometry Studio Make an angle to a target with a live protractor, build a polygon to a given interior-angle sum, and set complementary & supplementary pairs. Transformation Lab Slide, flip, turn, and scale shapes on a coordinate grid: name the transformation, tap where a vertex lands, and find a shape’s line of symmetry. Geoboard Stretch a rubber band around the pegs to enclose an exact area — and watch Pick’s Theorem balance as you drag. Concept practice 17 short question rounds, from points & angles up to advanced synthesis — pick one below.

Practice the concepts

17 kits from an intro to points & angles up to advanced synthesis — a short round of questions with a hint whenever you get stuck. Your progress stays on this device.

Play together · new on the web

Geometry Duel — a head-to-head kit round for 2–4 players. Take turns on one device, or join a friend in an online room by code. Highest first-try score wins; no chat, no accounts.

⚔️ Start a Geometry Duel →

🔀 Mixed practice — revisit what you’ve learned A short round that shuffles questions from the kits you’ve played, brought back when they’re ready to review. Great for making it stick.