Enemies are in! Well, for now they've just got placeholder graphics, but the mechanics are all there - you can kill 'em, they walk around avoiding falling off ledges and stuff, and if you hit them they start chasing you if they were facing away from you (they take a few hits to kill).
Next on the agenda is to draw the actual sprites.. once I have that done, I'll be posting a few screenshots here, so stay tuned! In the meantime, here's a dancing Mike Tyson.
p.s. Sadly I can't take credit for the Tyson, I discovered it here.