Lights Out
A grid of lights, all of which have to end up off. Pressing one toggles it and its four neighbours, so every press undoes part of your last one. There is no penalty for a wrong move — the only score is how few presses it takes.
How it works
- Turn off every light on the board.
- Pressing a tile toggles itself and its neighbours above, below, left and right.
- Every move is reversible: pressing the same tile twice cancels it.
- A hint performs one press from a valid solution.
- There are no mistake penalties — solve it in as few moves as you can.
Good if you want…
- No reading and one rule to learn
- A puzzle with nothing to lose
- Something quick that still needs thinking about
How to solve Lights Out
Order does not matter
Two facts make Lights Out much easier than it first looks. Pressing a tile twice is the same as not pressing it at all, and the order you press tiles in makes no difference to where you end up. So a solution is really a set of tiles, each pressed once — the puzzle is working out which ones.
Chase the lights down
The standard method is called chasing. For every light still on in the top row, press the tile directly beneath it in the second row. That switches the top-row light off without touching the rest of the top row. Then do the same for the second row using the third, and so on down the board. When you reach the bottom, every light is off except, possibly, a few in the last row.
Fix the bottom row from the top
If lights are left in the bottom row, the fix is a particular set of presses in the top row, after which you chase down again. Which top-row presses clear which bottom-row pattern depends on the board's size, and working it out on a small board is a satisfying puzzle of its own. Pay attention to what each top-row press does to the bottom row after a chase, and the pattern soon becomes familiar.
Keep the count low
There is no penalty for a wrong press, but the score is how few presses you take. Because pressing twice cancels out, a solution never needs the same tile twice — if you notice you have pressed a tile an even number of times, those presses were wasted.
Common mistakes
- Pressing lit tiles directly. Pressing a light turns it off but flips its neighbours, which usually makes things worse.
- Chasing in two directions at once. Pick top to bottom and stick to it.
Where Lights Out comes from
Lights Out was released as a handheld electronic game in 1995. It has since become a favourite example in mathematics teaching, because solving it is really a problem in linear algebra: each light is a switch that is either on or off, and every press adds the same pattern to the board.
Lights Out questions
Is every Lights Out board solvable?
Not every arrangement of lights can be switched off on every size of board. Every board in Winters Puzzles is dealt from a solvable position, and a hint performs one press from a valid solution.
Does a wrong press cost me anything?
No. Every press can be undone by pressing the same tile again. The only measure is how few presses you take.
Lights Out in Winters Puzzles
Lights Out is one of 40 puzzles in Winters Puzzles, so it sits alongside Patch, Logic Grid, Pippin and everything else in the app rather than being a download of its own. It counts towards your stats and streak like any other puzzle. It is not one of the puzzle types included in Pip’s dailies.
Play Lights Out.
Free on iPhone and iPad, with 39 other puzzles alongside it. Or play it in your browser — no download, nothing to sign up for.
