i played through the whole thing and it's... ok.
it's boring. I appreciate variety but the level design doesn't compensate, it's your typical run and jump hack, very similar to SMB1. There are a few engaging moments, like jumping between blocks with munchers on timed lift in DESERT HILLS 3
and autoscrolling section with fire monsters in DESERT CASTLE
, but they are far in-between. Also I think you should remove most of your "springboard puzzles" where you enter a pipe, pick up springboard and bring it to where you need it. (sometimes it's a p-switch, but idea is the same). They feel like a waste of time and add nothing to the gameplay. Aesthetics look alright at least. And there are a few technical issues. I noticed a bit of slowdown, but other than that:
-Black status bar text
-I can just pass through those key doors, without need to solve "puzzles"
5/10. I think it's kind of mediocre.