Lights Out puzzle — tap any cell to toggle it and its neighbors. Turn every light off to clear the board.
Tap a cell to toggle it AND the 4 adjacent cells (up/down/left/right).
Goal: turn all lights off.
Fewer moves and faster time = better score.
Lights Out looks like trial and error but it is pure logic, and the key fact is that order does not matter — only whether each cell is pressed an odd or even number of times. Pressing the same cell twice cancels out, so never undo a move by repeating it; plan instead so every cell you touch is touched exactly once.
The classic method is "chase the lights": clear the top row by pressing the cell directly below each lit one, which pushes all the remaining lights down a row. Repeat until only the bottom row has lights, and that final pattern tells you which cells in the very top row to press to finish. Fewer total moves scores better, so once you know the technique, look for symmetry to trim wasted presses.