The objective is to score as many points as possible by making balls of one color form various lines.
First select the ball to be moved, then an empty destination square. If the destination square is occupied by another ball,
that ball is now selected to be moved. Note that you cannot always place the
ball where you'd want to. After you move a ball, three more appear, except when you formed a line.
The more balls in a shape, the more points you score for making it.