Ah, a big ball bouncing around the screen. Although a bit of a cliché, it's one of my favorite demos. It manages a large area of full resolution graphics without any flicker or other compromises.
The demo only works on a TRS-80 Model III, but it could be made to work on a Model I. Might need to have a slightly smaller ball.
InstructionsPress keys 1 though 7 to speed up the ball's motion. 1 makes it go a bit faster, 7 a lot faster. And holding all of them down will make it go at top speed.
George Phillips, July 3, 2009. george -at- 48k.ca