Cosmic Crusader

Cosmic Crusader is to Galaxian as Space Strike (by the same programmer) was to Space Invaders. An alien space fleet has discovered the location of Earth, and – being an alien space fleet – immediately sets out on the attack. The only thing standing between the enemy and total Terran termination is you – the player, with your puny gunship that’s stuck to the bottom of the screen and can only move left and right.