Hey, pretty cool game you got here!
It's definitely not the most impressive game from a graphical standpoint or anything like that, but the core gameplay mechanics of blasting around with the shotgun felt very satisfying and intriguing to get skilled at, and when you top that off with a great sense of progression through a combination of upgrades/level changes/boss fights/story beats as well as cool music (albeit cool music that doesn't loop properly) it made this a great little adventure! Also felt pretty well-polished: for example, I loved the little touch of the pitch-shifting for the depleting ammo as it really helped teach the ammo mechanics in a subtle way!
There definitely is some clunkiness to the game: as stated before, the music doesn't loop properly, and furthermore there are some weird bugs here and there and unbalanced upgrades and the shotgun controls can be a bit frustrating to get used to and the checkpoints are sometimes too harsh/too forgiving and so on. I also felt really annoyed that it didn't have a save/load mechanic. But despite all that, I felt like this was pretty fun nonetheless, or at the very least, a great prototype that makes me want to see a more polished final version, so I'd say that's a good game jam result!