How to play Lights Out
Lights Out is a grid of lights and a single rule: pressing a light flips it and its four neighbours — on goes off, off goes on. Switch every light off to clear the board.
Each board shows its par, the fewest presses that can solve it. Hitting par is the real game; the clock ranks your hint-free solves.
Rules
- Pressing a cell toggles that cell and the cells directly above, below, left and right of it. Edge and corner cells have fewer neighbours.
- The board is solved when every light is off.
- Order never matters, and pressing the same cell twice cancels out — so every solution is really just a set of cells to press once.
- Every board is made by pressing random cells of a dark grid, so it can always be solved. Par is the smallest set of presses that does it, worked out exactly for that board.
- Three sizes: Warm-up (3×3), Classic (5×5) and Large (7×7). Each keeps its own board in progress, best time and leaderboard.
- The clock starts with your first press. A hint highlights one cell of the shortest solution from where the board stands now; a hinted solve is saved but not ranked.
Controls
- Click / tap
- Press a light
- Arrows / WASD
- Move the keyboard cursor
- Enter / Space
- Press the light under the cursor
- Z / U / Backspace
- Undo the last press
- R
- Restart the board as it was dealt (the clock keeps running)
- H
- Hint: show one press of the shortest solution
- P
- Pause and resume
Tips
- Chase the lights: work down the board row by row, and for every light still on, press the cell directly below it. Each row ends up dark, and only the bottom row is left.
- On the 5×5, the lit pattern left on the bottom row tells you which top-row cells to press before chasing again — a few patterns are worth memorising.
- Undo is free, but restarting from the dealt board is often quicker than unpicking a long run of presses.
Lights Out strategy
Two sizes have one answer
On these two sizes every board has exactly one set of presses that solves it. Any solve where you press each cell at most once is a par solve. If you finish over par, you pressed some cell twice, and each double press costs two moves. Undo takes a press back off the count, but only the latest one, so a double press spotted late is easier to fix with the replay below.
Restart to bank a clean run
Chasing the lights solves the board but usually wanders, pressing some cells twice. Restart clears the presses, though the clock keeps running. So chase once to learn the answer, note which cells you pressed an odd number of times, then restart and press only those. On 3 × 3 and 7 × 7 that replay is par.
The 5 × 5 bottom-row table
After chasing a 5 × 5, only seven bottom-row patterns can remain. Counting cells from the left: lights 1, 2, 4 and 5 lit, press top cell 3. Lights 1, 3 and 4, press top cell 5. Lights 1, 2 and 3, press top cell 2. Lights 2, 3 and 5, press top cell 1. Lights 3, 4 and 5, press top cell 4. Lights 1 and 5, press top cells 1 and 2. Lights 2 and 4, press top cells 1 and 4. Then chase again.
Trimming a 5 × 5 to par
A 5 × 5 board has four solutions, and they differ by patterns that change nothing when pressed. One is columns 1, 3 and 5 in every row except the middle. Another is columns 1, 2, 4 and 5 in rows 1, 3 and 5. If your replay set contains more than half of one of these patterns, swap it: skip the shared cells and press the pattern’s others instead. The result is shorter.
About Lights Out
Lights Out was a handheld electronic puzzle released by Tiger Electronics in 1995: a 5×5 grid of rubbery light-up buttons and a stack of built-in boards. It became a minor classic of the toy aisle and a favourite of mathematicians, because the whole puzzle turns out to be a system of linear equations over the numbers 0 and 1.
This browser version generates its own boards and solves each one exactly with that linear algebra, which is how it knows par. On the 5×5 board four different press sets always lead to the same result, and par is the shortest of them.
Questions
Is every Lights Out board solvable?
Every board here is. They are made by pressing random cells of a dark grid, so undoing those presses always works — and the game computes the shortest way to do it, shown as par.
What does par mean in Lights Out?
The fewest presses that solve the board you were dealt. It is worked out exactly, so finishing in par moves means you found an optimal solution.
Is there a trick to solving Lights Out?
Yes: chase the lights. Press the cell under every lit light, row by row, until only the bottom row is lit. The pattern left there tells you which top-row cells to press before chasing again.
Do hints count against me?
A solve that used a hint is saved in your history but does not count for your best time or the leaderboard.