Light every crystal. Emitters fire beams; walls stop them; crystals let light pass through.
Tap an empty tile to cycle: / mirror, \ mirror, then glass splitters (if you have any), then empty. Right-click cycles backwards.
A splitter lets light through and reflects it.
Crystals need their exact color: gold, red, blue, or violet = red + blue. The wrong color darkens a crystal. Each color also has a mark: red = diamond, blue = ring, violet = half-filled circle, gold = dot.
Colored filters only let their own color through. Splitters pass and reflect every color.
Keys: Z undo, R reset (after a win: replay), H hint, N next.
Every generated puzzle is checked by a solver to have exactly one solution.