A continuous-angle companion to Mirror Maze's grid puzzle: instead of snapping to 45° diagonals, both mirrors rotate freely, so you can watch the law of reflection hold exactly at any angle, not just the four the grid allows.
Angle of incidence equals angle of reflection, measured live from the true surface normal via vector reflection (d′ = d − 2(d·n)n) rather than a lookup table — the same law that governs the grid-based Mirror Maze, made continuous.
Aim the beam and tilt each mirror with the sliders until the ray reaches the photosensor. Toggle surface normals to see the reference line each reflection angle is measured against.
Corner-cube retroreflectors — three mirrors at exactly 90° to each other — send any incoming ray straight back the way it came, which is why bicycle reflectors and the mirrors left on the Moon by Apollo astronauts still work from any angle.