Guardian

Guardian is the best clone of the arcade game Defender that the Coco had (and it only works on a Coco 1 or 2, due to it's use of a non-standard Semi-graphics mode. There was going to be a much better Coco 3 only version called "Defendroid" from Oblique Triad, but that one was never released). Using a strange variation of the Semigraphics-24 mode (64x192 9 color) which actually defined the screen to be wider than the normal 32 bytes it would be, John Kowalski (Sockmaster) speculates that it was done to cut down on clipping calculations at either side of the screen, since you could just draw the shape (letting it go past the edge) without any special checks, and without the shape wrapping over to the other side of the screen. As far as he knows, NO other program on the Coco used this mode (it broke most emulators for awhile, although some now do support it)

The basic premise of the game is the same as Defender - destroy ships and rescue humans. Like the arcade, the aliens implode from particles, and your planet will also blow up if all the humans are lost. You also have the radar from the original, and smart bombs that will detonate everyting on the current viewable screen (but nothing beyond, that you can see in the radar window).

An excellent game, and one of the best uses of the highest resolution semi-graphics mode, with excellent sound as well.