Tested your demo.
In general, the level design was average. It didn't feel boring, but it wasn't super amazing either.
Koopas and Goombas were pretty much everywhere, and while those guys are all good, you should use more enemy variety, especially non-grounded enemies (anything that flies, jumps, levitates, rotates in the air, etc). Also, one or two enemies
here would have been nice.
The level with the FLUDD was okay, and the gimmick was nicely implemented, but the secret exit was way too easy to find, even for world 1. You should hide it better.
The Yellow Switch Palace, had a good concept, but when I get
here I have to wait for the three block platform and do nothing.
The first room in the castle can also be improved, you used a lot of platforms with just one enemy or that simply required running bellow spikes. Also, it's nice that you used Ersanio's ice key, but try to use it in a way that doesn't require babysitting it back and fort because it's too repetitive that way, (and you really don't need a key for that, usisng two P-switches can give you the same result). The second room of the castle was nice, but the boss felt a bit hard for world 1, maybe you should move the midpoint before the boss.
The wind gimmick in the world 2 level is interesting, but I feel it could have been implemented better. For now all it does is pushing the player backwards, try to make it blend with the design, for example, you can add some walls with munchers so the player will have to avoid being pushed there, just a suggestion.
On the good side, I liked the beach level, that part with the disco shell was pretty fun.
As I said, the design is acceptable. It's not bad, but with some polishing you can make it stand out. I have to say you've improved a lot since I used to reject your hacks back in 2012.
