The design here is okay. It's mostly linear, but the gimmicks used in it make the whole demo pretty fun to play. Each level features its own gimmick, set of enemies and mechanics, and it's overall enjoyable. There are a few small design issues I could point out, like the fact that many sections imply blind falls, but hopefully they don't penalize the hack too much. For a world 1, I guess it's a good start.
Aesthetic-wise, could've been better. There's some clashyness going on (like the fact the author uses the barrels from DKC, and didn't edit their GFX to make it fit in the SMB3 style), as well as some noticeable cutoff. The titlescreen also is awful, it has a very bad impact on the player.