Positron is a video game made for the BBC Micro computer by the programmer Gary Partis in 1983, released by Superior Software.
The player controls a space ship, at the bottom of the screen, vertical motion is not possible. The object of the game is to destroy all alien creatures on each screen, then proceed to the next. The first wave of aliens follows the classic Space Invaders style of moving, subsequent waves apparently have no pattern of positioning.
The aliens are called, in order of appearance - Cyber, Spazmoid, Galactic Hulk, Hep-Hep, Graber, Bum-Fluff, Phantom, Orb and Mega-Bod. Destroying the mothership which appears above the Mega-bods ends the current level, and starts you again from the beginning, with faster enemies.