Galactic Invasion

Galactic Invasion is a game released for the Bally Astrocade. It was originally called Galaxian, but copyright issues forced the name to be changed.

Gameplay
It is a shoot 'em up in which the player is at the bottom of the screen, with an arrangement of aliens at the top. The player moves left and right to aim at an alien, then shoots a bullet up the screen, and the alien it hits is killed. At set intervals an enemy will move down the screen towards you, escorting a bomber, which is a moment of high danger. Clear a wave and another is generated.