From MG Software:
In this simple but addictive game, the playing field is filled with colored blocks. The object of the game is to remove all the blocks from the playing field. Do this by shifting and swapping blocks so that three blocks of the same color form a vertical or horizontal line. When three blocks form a line, they are removed from the playing field and any blocks above them drop down. To swap two blocks just position the mouse over them and click the left mouse button. To shift a row or column of blocks just click on the arrows.