There is only one action available in Lights Off: clicking a tile on the board. You can either click on the tile with the mouse, or use the arrow keys to choose it. The first time you press an arrow key during a game of Lights Off, a cursor will appear, which you can move with the keyboard; pressing enter will click the light below the cursor.

When a tile is clicked, both it and all of its non-diagonal neighbors will toggle their state. The objective is to turn all of the tiles on the board off.

To begin a new game, go to Game ▸ New Game. The progression of levels will be the same between games and between computers, so New Game should only be chosen if you actually want to return to the beginning of the game.