Planet Invasion is a clone of the arcade hit Defender. It features pretty well all of the nuances of the arcade game (smart bombs, radar, humans to rescue, hyperspace), but the shapes are a lot smaller than in the arcade, and the 'feel' when flying is not too similiar to the arcade. Still, a very good clone, though.
Title: Planet Invasion
Author: Steve Gieseking
Publisher: Spectral Associates
Released: November 1982
Requires: Color Computer 1,2,3, 16K RAM, tape or disk, joystick.