Each sand timer is filled with a different amount of sand. Set the clocks and start the game by pressing your button. Using one hand, you've got to keep the sand flowing by flipping and moving the timers to an empty space one at a time.
Stay focused and move fast... The instant a timer runs out, your opponent gets to hit their button to stop your count-down and start theirs before jumping right into the sand-flippin' action. Whoever can run out their clock first wins the game!