About Lights Out
Lights Out is a 5 x 5 grid of lights where each press flips the light you touch and the four lights directly next to it. The aim is to switch every light off. Clearing a board takes you to the next level, which starts more scrambled than the last.
How to play
- Pressing a light toggles it and its neighbours above, below, left and right. Diagonal neighbours are not affected, and lights on the edge simply have fewer neighbours.
- A level is cleared when all 25 lights are off.
- Each board is made by pressing random lights on a dark board: 5 presses on level 1, and 2 more for every level after that. Because of this, every board can be solved.
- Clearing a board adds about 100 minus the number of presses you used (never less than 10 points) to your running score.
- Your score keeps adding up as you move through the levels, and the running total is what counts as your best.
- New board deals a different puzzle at the same level and resets the move counter, but keeps your score.
Controls
- Mouse or touch: click or tap a light to press it.
- After clearing a board, the Play again button moves you to the next level.
- There is no keyboard control for this game.
Tips and strategy
- Pressing the same light twice undoes it, and the order of presses does not matter. A solution is just a set of lights to press once each.
- Use light chasing: for each lit light in the top row, press the light directly below it. Repeat row by row, and every light except those in the bottom row will be off.
- After chasing, the pattern left on the bottom row tells you which top-row lights to press before chasing again. For example, if only the first three bottom lights remain lit, press the second light in the top row, then chase down again.
- Early levels are made from only a few random presses, so look for a plus-shaped group of five lit lights; one press in its centre clears it.
- Because random presses can cancel each other out, a board is often easier than its level number suggests. Spend a moment looking before you start chasing.
Background
Lights Out was released as a handheld electronic game by Tiger Electronics in 1995, with a 5 x 5 grid of light-up buttons. The puzzle has a neat mathematical side: because each press simply flips lights on or off, solving it is equivalent to solving a system of linear equations where 1 + 1 = 0. That analysis also shows that on a 5 x 5 board not every pattern can be solved, which is why this version builds each level from presses on a dark board.
Questions
- Is every board solvable?
- Yes. Each board is created by pressing random lights starting from all-off, so pressing those same lights again would solve it.
- Does my score reset when I get a new board?
- No. New board only replaces the current puzzle and resets the move count. Your running score stays until you reload the page.