Space Zap is a clone of the 1980 arcade game of the same name that was produced by Midway. It auto selects the joystick the player wants by their hitting one of the joystick buttons, and also saves the top 10 scores (with full names) to disk. The gameplay is fairly simple: You are the ship in the middle of the screen, and enemy ships show up from 4 directions and fire on you. One of your shots can take out an enemy shot or ship, but not both with the same shot. At the end of each wave, a killer satellite circles around your base and you have to destroy it before it destroys you. Each wave gets faster and faster, with both the opponent shots speeding up and sudden appearing and disappearing if the alien ships speeding up as well. The main fire button shoots your lasers in one of the four directions; the 2nd button (or SPACEBAR) is your Super Zapper, which will destroy everything on the screen (enemy shots and ships)... but you only have 3 of these to start. You can earn extra ships and super zappers at certain scores.
In current versions of NitrOS9, the game can get quite fast on later levels. The game is written entirely in BASIC09, and I think it could run on a 128K Coco 3 if one made a custom boot. You can download it as part of NitrOS9/EOU (Ease of Use) (see download link below).
Title: Space Zap
Author: Floyd Resler
Publisher: Shareware via Compuserve
Released: 1990
Requires: Color Computer 3, 256K RAM, disk, joystick (2 button optional).