LabCaustyx: Light, traced by hand

Caustyx is a CPU ray tracer written from scratch: it builds up Vec3 algebra, ray-sphere intersection, Phong shading, hard shadows and recursive mirror reflections, then cleans the edges with 2x supersampling. The core intersection and shading math is covered by 13 tests. A dependency-light build you can download and run locally to see how rendering works under the hood.