Frame rate issues become a big problem
In a platformer game that requires precise positioning or else death occurs, and which has a finnicky sense of momentum, losing random frames during jumps (and sometimes even just walking!) becomes a huge problem. Even at low quality, the game was rather choppy on my 4 year old computer. I suggest trying to optimize code or figuring out some way to reduce the graphics load the next time you make this sort of a game. For instance, I think you've been using transparency to handle the faded appearance of the bottom portion and the person. Since the background is just white anyway, you could do the same effect by just redrawing the objects in lighter shades.