The object of the game is to capture pieces, which is done by causing eruptions. Whenever an erupting piece lands upon a piece of its same size, you capture the erupting piece.

For example, if you move a cap such that the erupting large lands upon a large, and the medium further lands upon a medium, you would remove those two pieces from the board and set them in front of you.

Only the topmost piece can be matched by the erupting piece to make a capture.