http://www.cloudsprinter.com/software/

Another big thing is that it runs a bit too slowly, even on a StrongARM. A quick hack around in the code (For your own benefit, of course) reveals that you're using OS_SpriteOp commands to draw the sprites, and that the game is programmed in BASIC. Although this itself is not a bad thing, it's worth noting that OS_SpriteOp is horribly slow compared to writing your own routines in ARM code.

Assuming that you don't know ARM code (Or C/C++), my advice would be to try and cut down the number of sprites you draw each frame. Instead of redrawing the entire level, why not just redraw the sprites which are near the probe and the mouse? It's a technique which I've used myself to get a great speed boost.

You also seem to have a 20fps limit on the speed - although this may be useful for doing animations, when playing the game it's a lot better to have the mouse updated as often as possible so that it doesn't appear sluggish to use.

Hope that helps.