It's best not to play this game while you're at work--because you may find yourself still playing it when you should be working!
The object of the game is get the Rocks to pass through the gates to the bottom. Each rock which makes it to the bottom will increase your score by one. Enter the rocks in the top green starting lanes by clicking in the green lane you wish to start with. You and the computer will take turns adding rocks to the board. If two or more rocks fall through to the bottom in a single turn, the player gets another turn.