It's exceedingly rough and a pretty simple effect that I'm sure has been exploited a hundred times before but I thought I'd throw it up as is as my part in maintaining the fantastic momentum we've had lately.
http://www.clocksignal.com/dropbox/scroller.dsk It's explicitly not a mere demo effect; adding some sprites and making a full game is a definite possibility, though you'd probably want to drop to 25fps — there's loads of memory free even on a 256kb machine and it's a full, genuine Mode 4 display. The map itself is just an array of bytes in memory, so there's no real magic there and no huge footprint. The workflow is based on a cross-platform map editor called Tiled so that's easy to manage. Beyond my painful lack of artistic ability there's no reason why it need use only one tile. Ditto for proper clipping at the edges (which, because the tiles are precompiled, would cost more RAM but not really any more processing). It was full screen until the last minute, when I discovered that some sections of the horrid little map I've hastily scribbled were a little too slow. As you'd expect on a Sam, the trick is painting only where you need to so level design affects speed in a less obvious manner than being directly tied to screen area.
