The only thing standing between Earth and utter destruction from wave after wave of evil boss monsters is a cat. With a jetpack. Whose name is? (dramatic pause) Plonzo....
Click the power balls to load and fire Plonzo's laser cannon. Don't over fill it. And don't go take too long, or the jetpack will overheat. Shooting the cannon is automatic when the energy level reaches full (and not over-full)