How to play Lights Out
- Pick a board size. 5 × 5 is the classic puzzle; 3 × 3 is a quick warm-up.
- Click any light to switch it, along with the lights directly above, below, left and right of it. Lights that were on go off, and lights that were off come on.
- Turn every light off. The counter shows your presses next to the fewest the puzzle needs.
Tips for Lights Out
Light chasing works on any board: clear it row by row from the top by pressing under every lit light, and what’s left at the bottom shows what to change at the top. A plus shape of five lit lights goes out with a single press in its middle, so look for those first.
Two presses on the same light cancel out, so a light you’ve already pressed never needs pressing again. If the counter is well past the fewest possible presses, restart and look for a shorter route.
About the puzzle
Lights Out was released as a handheld electronic game in 1995, with a 5 × 5 grid of lit buttons. The puzzle became a favorite example in recreational mathematics, because it can be solved exactly with linear algebra and shows neatly why some starting patterns can never be cleared.