Lots of potential.
Chesse it more! Time can be limit, but with better time management I think you could add more ideas, like bigger variety of enemies (like one that is faster, or one that explodes when dies), more upgrades, more weapons(you mentioned that one)(would be cool if you made some kind of weapon for each of the theme, it would be hard tho), maybe even some boss fights?
Anyways I like the idea of having a choice of upgrades, I also love the concept of weapons (no need to click anything, it ll goes automatically with a cooldown!), the idea of an endless shooter isn't that original through.
Good job and better luck next time!
Next time add some UI and a way to exit your game through.