Wow this game is actually really cute and fun! You if you wanted to add anything more to it I would say maybe some music in the background but this is awesome :)
Note: If game is unresponsive to keyboard input, click on game area and then try again.
Z - FIRE
UP/DOWN ARROWS - to move up and down
Shoot balloons to knock the cavemen out of the air before they land. Try not to aim at the cavemen directly, as their shields will block your shot.