The idea of the game is great, and the art is also very good, but MAN this could need better level design. the difficulty ramps up a ton on layer 3, but I didn't find it the fun kind of difficulty. I think the biggest offender are the fireballs with short ranges. They reset constantly, and your character is quite floaty so it can be hard to calculate when you should move through. I found the part with the spring into a fireball especially annoying, because it was impossible to dodge the spring, and getting launched up meant instant death even with shields unless you immediately hold down. I later found the best way to dodge is to run forwards without jumping, which kinda invalidates the spring in the first place.
I ended up beating layer 3 once and died at 4, where I quit because I didn't want to go through the previous layers again. It seems like this game suffers from lack of playtesting, which is understandable considering 3 days to make a game doesn't make time for playtesting, and level design is really difficult to get right.
Sorry for being so negative in the review, the game is cool, but should be easier, or at least be less punishing.
Other things I forgot to mention:
I like the fastfalling
Character should decelerate faster, I had a couple deaths in the start where I ran into spikes because the player didn't stop moving fast enough when I released.
Camera should move faster when you're at the bottom, especially noticeable in layer 1
Resetting to the start was frustrating, but idk how this would be solved, maybe a lives system?