A single goal: to change the color of all the buttons from yellow to green.
A single rule: Pressing a button inverts the color of itself and adjacent buttons.
Every game is automatically saved so you can restore and continue the challenge.
You can change the grid from a minimum of 3 boxes per row and per column to the maximum allowed by the size of the screen with the minimum button size of 30x30.
It's also possible to start a game by a selectable number (1 to 4) of random moves, so as to make the game even more dynamic and unpredictable.