Lights Out
Every press flips a light and the four lights next to it. Can you switch the whole board off, and match the fewest possible moves?
How to Play
- Click a square (or move with the arrow keys and press Space) to press it.
- Pressing a square flips it, and the squares directly above, below, left and right of it, between on and off.
- The goal is to switch every light off.
- Par is the fewest presses that can solve the board. Match it for a perfect score.
- Hint marks a square that's part of a shortest solution from where you are now. Reset puts the board back to the start.
Tips & Strategy
- Pressing the same square twice cancels itself out, so a shortest solution never presses any square more than once.
- The order of presses doesn't matter: only which squares you press.
- Try "chasing the lights": clear each row by pressing the squares directly beneath its lit lights, working top to bottom. Then look at what's left on the bottom row.
- Corners and edges touch fewer squares, which makes them good for fine adjustments.
Frequently Asked Questions
Yes. Boards are made by pressing random squares on an empty board, so there's always a way back. Some light patterns on a 5x5 board can never be solved, and the game never gives you those.
The game treats the board as a system of equations where each light must be flipped an odd or even number of times, and solves it exactly. Par is the smallest number of presses among all the solutions.
At midnight in your own time zone. Everyone gets the same board on the same date.
It was released as a handheld electronic game in 1995. The mathematics behind it, linear algebra over the numbers 0 and 1, has been studied for much longer.
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