This game seems like its going to be super fun! The movement is fast and fluid, and in combination with the shooting it feels great, I like your powerup system and the graphics are absolutely gorgeous.
I feel like the gun's running out of ammo could do with something like a sound or visual effect, as a lot of the time I accidentally borked the reload minigame (great addition by the way) because I was holding down the shoot button and didn't realise that the minigame had triggered. Additionally, in my personal opinion I feel like its very easy to get overwhelmed at the shop, though maybe that's the feel you're going for. If not, maybe adding a force-field around the shop that keeps enemies out, but also pauses the timer could work?
Other than those two small (and quite subjective) issues, the game is great! I hope you manage to plow on and make the game as big and as great as it can be!