Before you start
Start here
The Geometry Lab Read a figure, conjecture the measure a theorem guarantees, then a pure engine confirms it and names the theorem. 
Proven, or Just Looks True? Measuring a diagram isn’t a proof — predict whether a claim is proven or breaks, then see the theorem or counterexample. 
Teach the Cast Teach a geometry idea to a peer still learning it — teaching makes it stick. 
Concept Practice 16 kits from constructions through coordinate proofs — anchored to HS geometry. All activities
Explore & prove
The Geometry Lab Angles, triangles, circles, similarity, right-triangle trig — conjecture the measure, then a pure engine confirms it and states the theorem. Proven, or Just Looks True? One counterexample can break a claim that “looks true” — predict proven-or-breaks, then see the exact counterexample figure. Trace the Locus A circle, a parabola, an ellipse — each is just the set of points obeying ONE distance rule. Test points, predict the shape, then watch a pure engine trace the whole conic. Pell's Workshop Build classical figures with only compass and straightedge — an equilateral triangle, a perpendicular bisector, a hexagon. Order the steps, then the engine shows why each is exact BY construction, not by measurement.
Practice & teach
Concept Practice Sixteen short kits across HS geometry, with hints when you want them. Teach the Cast A near-peer geometer is still learning an idea — teach it and catch their misconception. Mixed Practice A short round across the kits you’ve played, brought back to review (spaced so it sticks). Progress Your levels and how each strand is coming along — saved only on this device.
Concept Kits — 16 kits of geometry
Kit 1: Constructions Constructions — compass and straightedge · 25 questions Kit 2: Angles & Lines Angles and lines — parallel lines and angle relationships · 25 questions Kit 3: Triangle Congruence Triangle congruence — SSS, SAS, ASA, and CPCTC · 25 questions Kit 4: Similarity Similarity — same shape, proportional size · 25 questions Kit 5: Right-Triangle Trig Right-triangle trigonometry and the Pythagorean theorem · 25 questions Kit 6: The Unit Circle The unit circle — angles and coordinates · 25 questions Kit 7: Circles & Circle Theorems Circles — inscribed and central angles, chords · 25 questions Kit 8: Coordinate Geometry Coordinate geometry — distance, midpoint, and slope proofs · 25 questions Kit 9: Transformations & Symmetry Transformations — rigid motions and dilation · 25 questions Kit 10: Quadrilaterals Quadrilaterals — properties and classification · 25 questions Kit 11: Polygons & Area Polygons and area — perimeter, area, and regular polygons · 25 questions Kit 12: 3D Solids & Cross-Sections Three-dimensional solids — volume, surface area, and cross-sections · 25 questions Kit 13: Conic Sections Conic sections — slicing a cone · 25 questions Kit 14: Vectors Vectors — magnitude, direction, and operations · 25 questions Kit 15: Proof & Justification Proof and justification — from conjecture to certainty · 25 questions Kit 16: Capstone: The Locus Problem Capstone — conjecture and prove a locus or construction · 25 questions
Who you’ll meet
- Pell — builds figures with only compass and straightedge (constructions)
- Vireo — proves triangles congruent from the givens (SSS/SAS/ASA)
- Orin — reads right-triangle ratios and the unit circle (trig)
- Osgood — relates inscribed and central angles (circle theorems)
- Talise — proves it on the coordinate plane (distance, midpoint, slope)
- Castell — moves figures by rigid motions and dilation (transformations)
- Alba — slices solids and cones into cross-sections
- Renard — turns "it looks true" into "here’s WHY" (proof)
- Adisa — the mentor — conjecture from the drag, then prove it