The design is more or less good, although it doesn't have anything memorable in it. It's the classic traditional kind of design. It's slightly challengy from the beginning due to the way the enemies are placed, but the levels themselves aren't too hard. Nothing else to say, I guess.
Aesthetics could've been much better, since there are many levels where there is weird paletting (like the first level's BG). Maybe it's kind of clashy if you think that the castle has vanilla FG + Yoshi Island's FG in the same level. But this is just a niptick, the main bad thing is that some palettes look weird in general.
As only issue worth of mention, music breaks on accurate emulators.
Overall, 2/5. Generic small hack with nothing memorable in it.