Interesting stage. :)
- I don't know why it's defined as a 640*480 stage whereas all the sprites seem LR. Anyway, not a big deal.
- You should adjust screenleft and screenright to allow the players to go to the borders of the stage.
- Please crop the sprites in the SFF, it's taking space for nothing.
- May be better with some light shadows, but you may have wanted it like that anyway.