It's time to kill some big green nasty giants! Rebound the boulders they are throwing at your village and kill them. With a little practice you'll be killing giants right and left.

Use your mouse to draw lines that bounce the boulders back at the giants. The shorter the line, the stronger the bounce.
When you have killed all the giants on a level you move to the next level where there is one more giant throwing rocks at you, this also means there is one more to kill.