Not gonna lie, when I saw "Shop", I thought it was a literal shop that took USD and got scared. BIG relief it was not that. This was really fun! Great work! Super smooth mechanically.
I think the enemy diversity ramps too slowly at the start. Once I learned how to not get boxed in, the game was pretty easy until those damn medic fish showed up, and then it was a big difficulty spike for me. I didn't really understand what was happening until I'd spent about five minutes or so on that single stage. Because the camera is limited, it's hard to even discover they exist since you're always dodging away, and the fish chasing you are directly in the path between you and the medics. I just thought more fish were spawning so I kept swimming around.
I also wanted more upgrades, because I wanted more power :)
Great work!