From Eph Software:
Stones stack up row by row on a board. It's your job to knock them off before they fill up the entire board. Slide stones around to form a row of stones the same as the topmost row. The matching rows of stones are knocked off the board, preventing the stones from filling up the board. However, you have to match it before time runs out or the stones get set in place. Don't let them keep stacking up.