The object is to score as many points as possible while keeping the board as clear as possible. You can move pieces anywhere as long as there is a path. If you get five or more pieces in a row (horizontally, vertically, or diagonally), they disappear and you score. After every move, three new pieces are dropped randomly onto the board. When the board is full, the game is over. You can click the drop button to drop new pieces without moving.
Five pieces in a row are worth 1 point apiece, six pieces are worth 2 points apiece, seven pieces are worth 3 points, etc. In order to score high it is a good idea to set it up so a large number of pieces disappear in one move.