Turn every light off — the classic grid puzzle, free, with the strategy that actually solves it
Lights Out gives you a grid of lit tiles and one rule: pressing a tile toggles it and its neighbours. The goal is to turn everything off. It looks like trial and error and it is not — the puzzle has a complete mathematical solution, and once you know the structure, boards that seemed impossible become routine.
Look at which tiles are lit.
Press a tile — it toggles itself and its orthogonal neighbours.
Pressing the same tile twice undoes it, so order never matters.
Turn every light off to solve the board.
Boards get larger and start from harder configurations.
Every board here is made by starting from all-off and pressing three to six random tiles, so it is always solvable — in the worst case by pressing those same tiles again. The move counter shows how many presses you have used; a board generated from four presses can be cleared in four or fewer.
Each board you clear moves you up a level, and the highest level you have reached is saved as your best. Choose the grid size before you start; larger grids are harder because each press touches a smaller share of the board.
Systematic problem solving and the recognition that a puzzle has structure rather than requiring search. The key insight — that each tile is either pressed or not, and order is irrelevant — is a genuinely useful habit of mind. More logic games to try next: Circuit Builder and Shikaku. The full solving method, chase the lights down row by row, is in our Lights Out strategy guide.
Lights Out looks like trial and error, but it is linear algebra. Pressing a tile twice undoes it, and the order of presses never matters, so every solution is just a set of tiles each pressed once or not at all. Mathematicians solve it by writing the board as a system of equations in arithmetic modulo 2.
That structure also explains two facts players discover the hard way: some starting boards on some grid sizes cannot be solved at all, and on a 5 × 5 grid only a quarter of possible boards are solvable, each of those in four different ways. The skill it builds is recognising that a puzzle has structure worth analysing before searching.
Order never matters. Only the set of tiles you press matters, because pressing twice cancels out. That alone shrinks the problem enormously.
Use 'light chasing': work top row to bottom, pressing the tile directly below every lit tile to clear each row in turn.
After chasing, only the bottom row can still be lit. The pattern left there tells you which top-row tiles to press first.
Never press the same tile twice in one solution. If you want to, your plan is wrong.
On a 5×5 board, not every configuration is — the solvable ones form a subspace. Our boards are generated from a solved state by making valid moves, so every board you are given can be solved.
Clearing the grid row by row: for every lit tile in a row, press the tile beneath it. That clears the row and pushes the problem downward until only the last row remains.
No. Toggling is its own inverse, so only which tiles you press matters, not when.
Yes. Lights Out is a linear algebra problem over the two-element field, and that is how the solvable configurations are characterised.