Good atmosphere and really enjoyed the color palette. Good use of theme and requirement with a boss on the edge of the screen.
One thing I ran into was the screen scaling when I went fullscreen was still a bit wonky since I'm on an ultra wide monitor I was able to see behind the boss, and I was able to see further ahead of me than others.
The upgrade mechanics between levels was a nice surprise. When I first got there I thought I could only pick one, but next time realized I could take both upgrades lol.
Regardless, good job! Fun game!