Moves 0
Lit 0
Puzzle 1
Lights Out
Every tap flips that light and the four next to it. Switch them all off.
Arrow keys to move, space or enter to press
Arrow keys to move, space or enter to press
Lights Out is a 5 by 5 grid of lamps. Pressing any lamp flips it and the four lamps directly above, below, left and right of it — diagonals are untouched, and lamps on an edge simply have fewer neighbours to flip. The goal is to turn every light off. Your score is the number of presses it took, so fewer is better. Every puzzle here is built by starting from a dark board and pressing random lamps, which guarantees it can always be solved.
Two facts make this much easier than flailing. First, order does not matter: pressing A then B is the same as B then A, so you only need to decide which lamps to press, not when. Second, pressing the same lamp twice undoes it, so no lamp is ever worth pressing more than once. That leads to the standard technique, called chasing the lights: work down the board row by row, and whenever a lamp in the row above is still lit, press the lamp directly beneath it. By the time you reach the bottom the whole board is dark except possibly the last row, and the pattern left there tells you which lamps in the top row to press before chasing once more. Learn the handful of bottom-row patterns and you can solve any board in well under ten moves.