Instructions:

The objective of this game is to 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.