Just played through the game, and it's been fun... already went in one round and got to the 14th round!
I feel like the game lends into two builds, since the firerate is inversely proportional to the distance (as the dist. proportional to the time the bullet despawns), you are really encouraged to get close and just go ham on the fire rate. The only reason it doesn't work is consistency as a stray bullet can leave you w/o one, and the enemies get too fast that it becomes very dangerous. The other build, I feel like if the projectile speed upgrade increases movement speed and increased damage the more distance the bullet travels, there could've been a cool sniper build that contrasts with the close-range upgrade. From there it's a balance, and with great map design, the gameplay loop is elevated further.
Okay, okay, suggestions (and rambling) aside. Overall, I enjoyed it. The music changing dynamically with the world, and the enemies start to scale up, the little mini breaks with the upgrade screen, and generally I live with the aesthetic, makes this enjoyable!
P.S. Also, the shapes and different critters was so cool, although I think my dps build melted down the big ones, the small ones were giving me some nasty trouble
Thank you for submitting into the game jam!