I played this from start to finish in like, an hour's sitting. I was so disappointed when I realized i'd done everything. Seriously, the idea behind re-using the stages with new gimmicks from 64 and Sunshine is worked perfectly into 2D, especially with them being based off of previous levels in the 2D Mario series. Plus, the controls. It's a big step up from NSMB, which was already a pretty tight 2D Mario moveset. The only tiny nitpick I could have is that the walljump detection could be a bit faster, for like, instant jumps from wall to wall. Just me being pedantic, though. Also the visuals were great. Felt like an official GBA era game.
Seriously, make more. I loved this.
Everyone seems to complain about the controls so I will change that. I'll also try to fix the music bug and other stuff tomorrow.
I should also note that Can of Nothing composed the music but the song isn't fully completed yet, so it will get much much better by the time I release a new build after SAGE is over.