After playing more than a dozen bullet heaven survival games for this jam, I can say with certainty that this is my favorite! The art is cool, the soundtrack is a banger, and the mechanics are so finely tuned it almost hurts.
There's a nice mix of general and specific upgrades, and the weapon loadout was balanced. It never felt like there was an upgrade I didn't want.
The enemy variety encourages smart play. There was never a complacent moment, considering I had to watch out for nimble UFOs.
The difficulty is VERY BALANCED. Progression maps very nicely to enemy inflation. I never felt like I couldn't have maneuvered my way out of something, but I never felt unstoppable either, especially when the giant worms showed up.
My only criticism is that the audio is a bit imbalanced; some of the sound effects are a good deal louder than the music, especially the item pickup and player damage sounds. Those sound effects are also a bit loud; it regularly peaked over 0.0 dB.
Fantastic work!