To play Xpandaballs, you try to destroy balls by hitting them with other balls. Each ball requires a different number of hits to be destroyed. When the ball you fired stops bouncing off the walls of the iPhone screen, it expands to fill the space where it landed. If the ball hits the boundary line at the bottom, you lose a life. Different colored balls have different properties; my favorites are the yellow, which can safely hit the boundary, and blue, which destroys a ball with one hit.