Lights Out Game Online Free
Pressing a light switches it and the lights above, below, left and right of it. Turn every light off in as few presses as you can.
Tap a light to switch it and its four neighbours. Turn them all off.
What is Lights Out?
Lights Out is a switch puzzle played on a grid of lights. Pressing any light switches it and its four neighbours (up, down, left and right): lights that were on go off, and lights that were off come on. You win when every light is off.
It started as a handheld electronic game in 1995 and turned out to be a neat piece of mathematics. Pressing a light twice undoes it, and the order of presses doesn’t matter, so each light only needs to be pressed once or not at all. Finding which ones is a set of equations in odd and even numbers, which is how the hint here always knows the shortest way to finish.
How to play Lights Out Game
- Some lights start on. Tap a light to switch it and the lights directly above, below, left and right of it.
- Lights on the edge or in a corner have fewer neighbours, so they switch fewer lights.
- Keep pressing until every light is off. The line under the board shows your presses and the fewest possible from the start.
- Hint presses one light on a shortest route from where you are, Undo takes back a press, and Clear goes back to the start. Every puzzle can be solved.
Lights Out Game skills
- Logical reasoning
- Odd and even numbers
- Planning and spotting patterns
Level: Ages 7 and up
Tips for Lights Out
Chase the lights down: press each light in the row below a lit light, row by row. That clears every row except the bottom one.
The order of presses doesn’t matter, and pressing the same light twice does nothing, so you never need to press a light more than once.
On 5 × 5, the pattern left in the bottom row after chasing down tells you which top-row lights to press before chasing again.
Lights Out Game questions and answers
How do you play Lights Out?
Press a light to switch it and its four neighbours, above, below, left and right. Lights that were on turn off and lights that were off turn on. The goal is to turn every light off.
Can every Lights Out puzzle be solved?
Not every pattern of lights on a 5 × 5 board can be solved, but every puzzle here starts from all lights off with random presses, so there is always a solution.
What is the trick to solving Lights Out?
Use “chase the lights”: for every light that is on, press the light directly below it, working down the rows. This leaves lights only on the bottom row, and each bottom-row pattern tells you which lights on the top row to press before chasing down again.
Is Lights Out a math puzzle?
Yes. Each light ends up on or off depending on whether it and its neighbours were pressed an odd or even number of times, so solving it is a system of equations mod 2, a topic from linear algebra. The hint solves those equations exactly.
What is the fewest number of presses?
It depends on the puzzle. The line under the board shows the fewest presses needed from the starting position, so you can try to match it.