Starbase Defence 64

In Starbase Defense, you must protect six energy generators at the bottom of the screen from waves of attacking XENO aliens. When they hit energy lines, they transform into bombs and descend rapidly. You can only shoot them once they become bombs. Missing a shot may cost you a generator. When all generators are destroyed, the game ends. You control the crosshair with a joystick or, in the original version, with the Stack Light Rifle.