A ball is moving inside the square.Each side of the square has a particular color. The ball is also colored with one of these colors. All you have to do is to ensure that the ball will not strike the side with the very same color and you can do this by touching the screen and altering the ball's color. After each time that you change the ball's color, it will also alter the direction that it moves. You will lose if you stop working to change the ball's color correctly or if you alter it when it's not needed.