Tron

You move B.E.R.N.A.R.D left and right along the bottom of one side of the screen and must deflect shots from his cranial gun off the sloped ceiling and over to the other side of the screen, destroying the mega-protons as they float up. Your shots will mirror where you are standing, so if you want to destroy a mega-proton that is close to the centre, you must also stand close to the centre to deflect a narrow shot and the further away it is, the further away you must stand to deflect a wider shot. The game ends when five mega-protons reach the delta crystal and charge the cannon.