Lights Out
Toggle cells and their neighbors until the whole five-by-five grid is dark.
Moves
0
Click a cell to toggle it and its neighbors. Turn all lights off.
How to use Lights Out
- 01Each tap flips the cell you pressed plus the cells directly above, below, left and right of it.
- 02Work out an order that switches everything off — the aim is an entirely dark grid.
- 03Use reset for a fresh, guaranteed-solvable board.
About Lights Out
Lights Out is a puzzle in modular arithmetic disguised as a grid of buttons. Pressing a cell twice undoes itself, so only whether you press each cell matters, not the order — the whole puzzle reduces to solving a system of equations over two values.
That gives a reliable technique called chasing the lights: work down the grid pressing the cell directly below every lit cell until only the bottom row is lit, then use a known set of top-row presses to finish. Every board here is generated from a solved grid, so a solution always exists.
Frequently asked questions
- Is every board solvable?
- Yes. Boards are generated by applying random presses to a solved grid.
- Does the order of presses matter?
- No. Only the set of cells you press matters, because pressing a cell twice cancels out.
- What is the minimum number of moves?
- It varies by board, but a chasing-the-lights solution is usually within a few moves of optimal.
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