Every lamp you press flips itself and the four lamps around it. Switch the whole grid off and the puzzle is done.
It looks like a game of trial and error for about a minute, and then you notice it is nothing of the sort.
Press any lamp. It changes state, and so do the lamps directly above, below, left and right of it. Lamps on an edge simply have fewer neighbours to take with them.
The aim is a completely dark grid. The move counter is there if you want to beat your own number, but nothing is lost by taking longer.
Pressing the same lamp twice puts everything back exactly as it was, so nothing you do is permanent and undo is always there.
Pick a difficulty for a bigger grid and a longer scramble. Every puzzle on the board is built from its date, so everyone playing today gets the same one.
Not at all, which is the single most useful thing to know. Pressing A then B leaves the board exactly as pressing B then A would. A solution is a set of lamps, not a sequence.
Yes. Each board is made by starting from a dark grid and pressing a random handful of lamps, so pressing that same handful again always clears it.
Work top down. Clear the first row, then press whatever is directly under any lamp still lit to clear the next row, and repeat. When you reach the bottom the remaining pattern tells you which lamps in the top row you should have started with.
It works out a full solution from the board as it stands and shows you one lamp from it, so it still helps after you have pressed things of your own.
Lights Out was a handheld made by Tiger Electronics in 1995, a 5 by 5 pad of light up buttons and nothing else. The idea was older than the toy, but that little red box is what most people remember.
Underneath, it is linear algebra wearing a disguise. Because every press is its own opposite and the order never matters, the whole game is a system of equations where everything is either on or off, and solving a board is the same work as solving those equations.
That is also why some patterns on a 5 by 5 grid cannot be cleared at all. The presses available to you do not reach every possible arrangement of lights, which is a strange thing to discover in a children's toy.