The game consists of a 5 by 5 grid of lights. When the game
starts, a random number or a stored pattern of these lights is switched
on. Pressing any of the lights will toggle it and the four adjacent lights.
The goal of the puzzle is to switch all the lights off, preferably in as
few button presses as possible.
This is the description of the gameplay of the 1995 Tiger Toys device
that gave the concept its probably best known name, Lights Out. But the
idea is far older, and there are many variants to the rules.
Besides the standalone implementations, the concept has also been used as a