Thanks for all the feedback! I really appreciate it. To be completely honest, I was aware of some of the problems you mentioned, but I really wanted to submit something this year and I was running out of time. The weird physics and controls are just me being inexperienced. I haven't really made a platformer before so I was figuring things out on the go. The levels themselves were also rushed, as I made all four on the last day.
I also underestimated how unreadable and difficult the second and third levels were. They require doing things fast and sometimes in a specific order. They felt perfectly beatable to me, but it was because I knew exactly what to do. It sounds stupid now, but during the jam I failed to consider that other people wouldn't just understand everything imidiately, especially without a tutorial. This only highlights how important it is to involve other people in playtesting.
As for the boxes, I had some problems with them moving too fast and not falling where they should. As a fix I made some of them heavier than others. It was a very inelegant solution, but a a better hadn't occured to be at the time. The box in the third level blocking the acces to the purple button is something I didn't even realize could happen. They did get glitchy sometimes, but usually just flew ot of the screen (an issue, but not a gamebreaking one, I was in a rush so I let it be).
Overall, this isn't the best submission but I'm glad I participated at all. I'll keep improving and will hopefully make something more polished next year.