I went on and played up to World 10's castle. I take it that the levels are only hard because of how late-game this demo is.
First off, the way these levels look are amazing
. The colors and aesthetics are some of the best I've seen. You put in shading in your levels too, and under the bridge the overworld of world 10.
I do have some things to say about some of the levels. I'm only saying these things just to express how I feel about certain ideas of yours.
•I hope you aren't actually using that intro in the final version... jokes like those aren't funny or sophisticated.
•The wall-jumping is rather finicky for me. Luckily, I didn't need to wall-jump all that much, aside from the tutorial. Also, wall-jumping can randomly glitch out Mario's speed and clip him through a wall and kills him? I had that happen once while playing 9-2.
•Speaking of 9-2, the poison smog that slowly kills Mario is clever. I wish there was a hint telling the player that the smog is bad for Mario however. I didn't know what kept the meter from going down at the time.
•9-4 (lovely song choice BTW) had a mechanic that I didn't like; Magikoopa puzzles. IMO, they're annoying to pull off, especially when the blocks are above you, and raining down enemies (maybe I'm just impatient).
•The fishing boo boss was confusing. From my experience, bosses are usually defeated by attacking them with something. I couldn't figure out this fishing boo boss for the life of me until I heard hitting sound effects randomly. That's when it became clear.
•My favorite level that I played was 10-1, and it is mostly everything after the midpoint that was really good. The vertical section was just the right amount of difficulty, and the homing bullet bills are really good enemies to have for that area.
•I'm 99.9% sure this is not meant to be like this
. (Level 10-2 BTW).