I was trying to beat the final boss before commenting, but life got in the way/ I suck at video games :P. I wanted to give feedback before the rating period ends though, so here goes:
I really like this game a lot! I really like how well thought out all of the bosses were, and how many phases each one has. I found myself thinking about some of the rust attack patterns when I was bored at work, which is really a testament to how well designed the fights are. I also like how the gun feels - it being slower to aim and slowing down your fall both add a lot of nuance to the controls. Learning to use both of those features to the fullest make it feel like you're gaining system mastery, and not just optimal tactics for beating bosses. The graphics are really pretty too, the game has a strong visual language.
I know some others have had issues with the speed - I got used to it fairly quickly, but I would have appreciated the walking speed being just a smidge slower. I kept finding myself wishing that the slow walk button was mapped to S, too, since I don't think it did anything else was mapped there. If I'm really nitpicking I could say that the progression didn't feel very "Metroidvania-y" or that I wished there was music, but I would be lying if I said any of that really impacted my enjoyment.
Overall this is probably my favorite game I played this jam.