This is surely not one of the most polished demos as you pointed out, but at least it had some thought put into it. The design was mixed on both the simplistic and the hard side, which explains a few choices you went for.
The levels are pretty linear; not dragged on for too long and tried to implement custom blocks and sprites in creative ways. The chemicals level (the second I've played) was pretty straightforward and needed some thinking about what order you take every platform. That big boo boss was a clever idea; I'm normally not a fan of bosses that take multiple hits, but in that particular case, you nailed it. There's cutoff on both walls that went unnoticed though.
The space level... It took a while to find out that I needed one of the disco shells to get past an entire muncher floor during the first half, and if I killed both, I'd be equally screwed unless I brought a mushroom from earlier to walk into them. If it was for a Kaizo hack, I'd mention it was pretty easy, but since it's not, I didn't really like it.
Sunken Pirate Ship was annoying to finish, because not only did I face some difficulty spikes (such as a completely random ambush from an Eerie below a ceiling of munchers), I had to deal with the fact that if the moving water reaches you, the conveyors act wonky. Mountain Airship had far more improvement than the previous level. I legit hate Boom Boom's hitbox, as when it starts flying, I can hit it from below rather than on the top, and I don't think it makes sense putting two of them and calling it a day.
(Also, I could only find less than five dragon coins throughout this hack. Where are the others?)
Oddball Blocks was good. I could barely distinguish the green glass blocks from the grey glass blocks due to the brightness, but the overall experience was fine.
From what you've showed in your other hacks, you're improving steadily. You just need to prioritize level design from a normal player's perspective and you'd be on the right track. I hope you don't give up hacking despite the obstacles, and good luck with whatever you build.
