I used to have a platform game a year or two back that I cannot remember the name of. I thought it was called "switch" but there is something else called that. It was a 2d platform game, where the floor was black and the walls (well, really the gap between the floor and ceiling) were white and again the ceiling was black. They weren't flat. They had various cut outs and shapes in them. There will be a switch somewhere in the room, that when pressed, inverts the whole scene so you are now looking at an inverted selection. Instead of walking though the white areas stood on black, you were now walking through the black areas, stood on white... Its hard to explain.... I drew something in paint, with a before and after type thing going on. The red blob is actually a man. Ring any bells for anyone?