It's a game to pass the time... and ward off boredom. Balls fall from the top of the screen and accumulate at the bottom. When balls of the same color collide, they disappear. Sometimes, they take a neighboring ball with them. Tapping the right side of the screen moves the falling ball to the right. The same works if you tap the left side, moving the falling ball to the left. By changing the direction of the falling ball, you control whether or not collisions occur. A game ends when the pile of balls reaches the top of the screen.
The player can have more than one objective. They can try to delay the growth of the pile of balls, directing them to collide with others of the same color and disappear. They can also try to accelerate the growth of the pile, diverting balls from others of the same color in order to speed up the pile's growth and thus reduce the number of balls generated needed to reach the top of the screen.
Boredom is for passing the time without playing. The Perpetual mode generates an infinite falling of balls to be observed.
Balls fall, and you direct them to collide (or not) with others by controlling the stack.