Light every square. Walls block light. Bulbs must never face each other.
Tap — bulb → × → blank. Drag paints.
Hold or right-click — mark empty. Mark mode swaps the shortcuts.
Smooth squares are lit; hatched squares still need light.
More controls
Each number needs that many bulbs beside it. Grey means it needs more, blue means the count matches, and bright yellow means too many. A diagonal glow does not count as light.
Hint previews a move. Tap it again to apply.
Arrows move. Enter or Space cycles; Mark mode marks directly; X marks empty. Z undoes. Restart clears this puzzle; Undo restores it. Escape cancels a gesture.
For a larger board, choose Enlarge, then Pan in Settings.