Awesome game! Very well designed and polished. The art is tremendous and the music is some of the catchiest I've heard in the jam so far.
I felt there were some weaknesses in the level design, in my case with the introduction/tutorialization of mechanics. There are a few cases of mechanics that are either introduced while the level is trying to accomplish other things (leading to overcomplication), introduced at inopportune moments, or are not set up to clearly convey what's meant to be learned. The easiest example of this is the balloon tutorial at the start, but I had a few others that affected my playthrough. The dynamic for how lightning works and how to avoid it is something I didn't 100% understand even after beating the level. The first poker card platform appears on-screen much later than the pit of spikes and the enemy, which means bubble-jumping to get across will likely be on the player's mind long before they think to throw it at a new object, and the next few appearances don't make that platform easy to play or experiment with. If you go left when you first enter the casino, you'll run into a pretty hard enemy chaining challenge (which if this is the first level visited, this makes for a tough introduction of this mechanic). Even if you rough it out, it isn't clear that your destination is the wheel and not the platform, as you may not have had the chance to learn that mechanic yet. With teaching new mechanics, I've found it's beneficial to isolate the specific lesson you're trying to teach, and to follow it up with some easy and safe placements to familiarize the player with it.
I did also notice a few difficulty spikes which, at least in my experience, felt a little jarring. But there weren't tons of them.
To clarify, I don't think the level design is bad, just held back by a few issues here and there. The fun factor with the level layouts is definitely on-target, and there's clearly a lot of purpose behind everything. A lot of the platform sequences are very well-placed, there's enough repetition to keep everything flowing well, on the most part. The good definitely outweighs the bad.