I used the SNES's background mode 4 in this game, which supports 8-bit per pixel graphics (256 colors). It seems that this GBA thing doesn't support it. Interesting, I didn't know that existed.
One tip I can give you is to stay at the bottom of the screen, Luigi will always come out from the bottom, you just have to be careful with the others who also come out from there in addition to those already on the screen. Good luck!
