Light leaves the emitters. Bend it with mirrors so that every target is lit with exactly the right colour.
◆Emitter — fires a beam in the direction it points.
◎Target — must receive light matching the colour of its ring. Two beams landing on the same target mix (red + green = yellow).
╱Mirror — turns a beam 90°. Click it to flip between ╱ and ╲, click again to pick it back up.
◇Splitter — lets the beam pass straight through and reflects a copy.
▬Blocker — a wall you place yourself, to stop a spare beam going somewhere it shouldn't.
▦Filter (−) — strips the beam down to that colour. White through a red filter comes out red.
▩Dye (+) — the opposite: it adds a colour. Red through green dye comes out yellow.
◉Portal — light entering one end leaves the matching end still travelling the same way.
▷Diode — only passes light travelling the way the arrow points. Anything else stops dead.
◈Switch & door — light a switch and every door of that colour opens, which may free up a beam somewhere else entirely.
☢Mine — never let a beam touch one.
Select a piece below the board, then click an empty tile to place it. Right-click removes a piece instantly. R resets the level.