The game is played on a 3x3 grid of buttons that are either on or off. By pushing the buttons, you can toggle whether they are on or off. The object is to form a "magic square," which is achieved when all but the center button in the grid are "on."
The catch is that pushing a button affects the state of other buttons. If you push a button on a side, not only will that button's state be toggled, but the two other buttons on that side will be toggled as well. If you push a button in a corner, it and the three buttons adjacent to it (the two side buttons next to it along with the center button) will be toggled as well. If you push the center button, the center button and all four side buttons will be toggled.
The game will start with a random button configuration. Some may be trivial to solve, while others may be harder.
No matter what the initial configuration, it is always possible to solve the magic square in no more than nine moves. If you make more than nine moves to solve the puzzle, that means you pressed more buttons than you needed to.
There are two modes of play. One gives you unlimited moves, which gives you the freedom to use more button presses than are strictly necessary. The other does not allow you to use more than nine moves, thereby forcing you to devise an efficient solution.
You can save your game by bookmarking the page in the game you want to come back to later. This works for all pages of the game except for the first (which has "newgame" in the URL), so if you want to bookmark a particular puzzle from the beginning, you have to make at least one move first.