http://www.fileden.com/files/2006/12/22/543510/vdpbug.PNG By the way, it's a common VDP bug that even Genecyst emulates. The reason is simple: every sprite and tile in the scrolls have a priority bit, either low or high, that determine where do they appear. However, this only works between planes, not between sprites. Sprites are ordered according to their index in the sprite list (first sprite gets over the rest). This means that a low priority sprite can get over a high priority sprite. And since all sprites are taken as a single plane, funny things can happen when that situation is mixed with high priority scroll, like in the screenshot I just linked. I was gonna make a demo ROM about this, but I'm too lazy =P So I'm gonna ask you: how would you exploit this bug? I came with an idea, but I would like to see with what would you come up. It's always nice to see new ways to make unusual stuff out of hardware =] If you can make it into a working ROM, better, but if you just want to detail how would it work, it's fine. So, who starts?