Holy smokes the artstyle is Fantastic!
I enjoyed the premise and the controls felt pretty snappy!
I like the idea of things getting harder after each "round" and I can see the skeleton of such system. I understand the time constraints you work with in a jam like this, 4 days is very little time, and what you've managed to create is nothing short of amazing! But I kinda wished that the levels transformed a bit more between each "round". Maybe something to consider if you were to work on this project outside of the jam.
Really good work with the game :)