Hole Hunter - Atari - Arcade, Puzzle

You have 20 minutes left for you to hit the scampering mice with your hammer before you go for a picnic on this sunny morning. However, do not be hasty, or you will drop into the hole where the mice live. Also, beware of the snake whose bite is deadly. If you drop your hammer, you have to retrieve it. Now, hit as many mice as you can.