Art style is one of the strangest things I've ever seen, but it's super unique and I gotta give props for sticking to it and at least making it consistent.
As for the gameplay the one thing I wish it was is consistent. Jumping just doesn't work sometimes and it's super easy to get stuck between the tiny platforms. The little pause in between dying and restarting the level is a good way to reorient the player and give them time to think about their next steps, but I wish it was relegated to a button press because that little pause between tries is agonizing when this game is so difficult.
The 30 seconds angle is a good one, but isn't it kind of pointless when the lava kills you so much quicker? I never saw the timer run down in my playthrough because it was the lava that dictated whether I lived or died, not the timer. Also in games about dying a lot, it's important to not have the music restart over and over again. Its such a small tweak but it is grating to hear that same sting over and over again, accentuating failure.
The levels are actually pretty cleverly designed, though designed for a masochist. Some of the later ones are so ridiculously tight that it can be pretty frustrating. Again this just accentuates how important it is to have fixed the jumping early on. The levels are fine if they're difficult, but having to fight the levels AND the controls is too much.
Overall, I think you did a pretty solid job in such a short time. Plenty of levels, an interesting art style, and solid level design carry a precocious jump button and a masochistic difficulty curve.