Shoot by mashing or holding the 'x' button.
Aim your option buddy by holding the 'z' button (pauses the game as you're aiming).
Destroy the big 'eye' cores to earn power-ups and get a better fighting chance against evil.
Wreck havoc, destroy as much as possible for extra points!
Watch your shields (bottom of the game window), if they get depleted it's "game over, man!"