Follow the light.
This is a small, hands-on playground for geometric optics. Set something in the path of a beam and see what happens.
Prisms follow Snell’s law, including total internal reflection, with an illustrative Cauchy dispersion model. Lenses use the ideal thin-lens approximation. Colors and glow are artistic; diffraction, partial reflections, and interference are not simulated. Overlapping prisms are treated as one material at each point.