Hm. Because I have a grey key that doesn't appear in the right place. I also placed it elsewhere to see it it would work there, and it flickered on and off when the pinheads extended and went back in their block. Maybe that's because pinheads take way more than 2 sprites horizontally. I'll play around with it and see if I can make the other key appear. (Oh, and I just thought I may have done something very stupid, so don't invest time in this, maybe I just made a mistake )The gameboy can take 10 sprites per horizontal line before it starts flickering. But most enemies take up at least 2 sprites horizontally. If they're vertically separated the gameboy can handle up to 40 sprites. I don't know about game engine limits, but I think it can take quite a few enemies.