Neat little game, graphics are nice and consistent, the difficulty seems adjusted pretty well, although it's a bit short.
I like the idea of a bullet hell where you can shoot the bullets.
I couldn't figure out how to use rockets, and it would be nice if I could upgrade the actual spread of my weapon in some way, the linear firing system with all the 3D movements of enemies and enemies weapons felt a little static.
I'd recommend reworking the number system, I'm getting an NaN error, so you're trying to return a non-number integer as the amount of money I have, therefore I can't buy anything, so I can't comment on if this even works in game. Without upgrades or the ability to use my missiles, it's a hair frustrating.
Otherwise seems fun, but would like to play it with upgrades so I could get further. You may want to add in some way to recover health between waves since you've got a shop, or shields, or just something a little more, the big ol' shop window with only damage upgrades seems lonely.