Each square will be either lit or unlit.
The lighting and unlightinge of the selected square and the squares above, below, left and right will be reversed.
The game is cleared when all squares are turned off.

- Challenge mode: Each time you clear the level, the level increases and the number of squares increases, maiking it more difficult.
- Free mode: You can freely select the number of squares. You can also select a random number of squares.