This was the first real video game I wrote, originally over a weekend in the seventh grade. It then went on to win third place in a state math fair. :) It needs a TRS-80 Color Computer with Extended BASIC, at least 16K of RAM, and two joysticks. It probably can't be played in an emulator, because of the control system. (The screenshots here are mock-ups, accurate but enlarged.)
You face a single opponent: a flying saucer, similar to your own. Your goal is to destroy it before it destroys you. The enemy fires back only when fired upon, but it also moves randomly, and you have to move out of the way. Six shots destroy the enemy; three shots, or one contact, destroy you.
The most unusual thing about it is the control system. The CoCo joysticks were non-centering, analog pots, digitized to 64 values over each axis; but most games just emulated simple directional joysticks. In Saucer, the position of the stick maps to an absolute position on screen, with a granularity of about four pixels. Plus, although it's single-player, both joysticks are needed; one to control your ship (for running away), and the other your crosshairs (for firing).
The look of the game is partly inspired by vector-based games like Asteroids, Tempest, and Battlezone. (But there's no connection with the Atari game "Space Duel", which I learned of only recently.) The viewpoint is kind of a mix of omniscient (where you just shoot in the direction the ship is pointing) and first-person view (where you have crosshairs or the like).
One thing I wanted to do in "Saucer" was to get away from the idea of defeating an endless parade of pushover enemies. That's why it's "A Space Duel": You and your opponent are nearly evenly matched. You get one "life" (but several hits). And there's no scoring: you win, or you lose.
The version here isn't the original. I had a variety of undated versions (no dates on the CoCo!) across multiple cassette tapes. Around 1997 (when Saucer was already about 15 years old), I put together the best bits and cleaned it up a little. (It could still use a little more cleaning.) But it looks and plays the same.
I also wrote a separate intro program for the fair. This one I haven't cleaned up. The bit about the protective "field" that the enemy sometimes entered was just cover for a bug (fixed in this version) -- because any bug can become a feature, as long as it's documented. :)
Download Intro (ASCII)
Download Saucer (ASCII)