Lights Out Solver

Stuck on a Lights Out puzzle? Copy the lit squares onto this grid and the solver marks the shortest set of presses instantly. It also tells you when a pattern cannot be solved at all.

How to play Lights Out Solver

• The board is a grid of lights. Some start on; your goal is to switch every light off.
• Pressing a light toggles it and the lights directly above, below, left and right of it. Diagonals are not affected.
• Every puzzle can be solved. The Par number shows the fewest presses possible — try to match it.
• The order of presses does not matter, and pressing the same light twice cancels out.
• In Solver mode, copy any pattern of lit squares and the marked squares show exactly which ones to press.

Controls

• Tap / click a light to press it
• Arrow keys move, Space / Enter press, Z undo, H hint

Tips

• Choose the grid size first, then tap every square that is lit in your puzzle.
• Switch to Tap presses to follow the solution on the board: press each marked square and watch the lights go out.
• Press Play this pattern to turn your copied board into a playable puzzle with a move counter.

FAQ

How does the Lights Out solver work?

Each press flips a fixed set of lights, so the puzzle is a system of on/off equations. The solver eliminates them the same way you would solve simultaneous equations, using arithmetic where 1 + 1 = 0, then picks the answer with the fewest presses.

Why does the solver say there is no solution?

On some board sizes, including 4×4 and 5×5, certain patterns cannot be cleared no matter what you press. Check that you copied the lights exactly; a single wrong square can make a puzzle unsolvable.

Does the order of presses matter?

No. Every press simply flips the same lights, so you can press the marked squares in any order.