Faster difficulty scaling, level variety, stat balancing, and more description on controls. Thank you for pointing those out as I've been taking notes on other people's reviews on what to improve upon next. Thinking about the idea of adding in a boss monster every few difficulties pretty much gave me that spark of excitement as I imagined that it would be a pretty good addition to my game.
I wish I did more playtesting in my game but it was final exams in my school during the week of the jam so a chunk of my time was pretty much sliced off; I had to make a final dash during the jam's final hours before the rating phase.
Anyways, thanks a lot for the incredibly detailed feedback, I appreciate it and it will help me a lot when thinking about game design.