I absolutely adore this game. Insanely impressive for 18 days.
I'll echo what a lot of other people are saying about the movement and sound design being fantastic.
The visual designs of the different areas are as distinct as they are lovely to look at. A lot of the enemy designs gave me big Cave Story vibes in the best way.
I really enjoyed the level design on the whole, but especially the way the Slam and Lambaste enemies were used in a number of sections to keep you on the move (and moving is super fun in this game). The variety of different slopes are used really well to create a lot of unique and interesting areas.
I love the extra bits on detail on the street lamps you can shake around and all the great animations on the square.
The catharsis of getting the missile upgrade and getting to blow up all the enemies you previously had to dodge around was a great moment too.
I found the telegraphing of attacks from the later bosses to be a little lackluster (Nemesis especially). I felt like I more-so had to get lucky to beat them as opposed to understanding their patterns and tells and outmaneuvering them. The fact there as many bosses as there are kinda blows my mind though.
I also wish the punch attack had a little bit more range to it, but I understand why it's the way it is.
Thanks so much for making this game! Amazing work; I had a blast.
P.S. I found this bug when transitioning screens. I imagine you've seen it, but I just wanted to make sure.