This is a neat little concept, with some elegant design! Forcing the players to choose an upgrade is well thought out, and leads to some interesting tactical decision making.
The game could benefit from some more enemy types, but just the one is fine for a jam game. I wonder if the upgrades would make more sense with the downsides removed? I don't know how you were balancing the numbers under the hood but if the power-ups were only ever gains then the game would become more frantic the longer it goes on as you wouldn't be canceling out past upgrades. A little game juice (screen shake, more impactful sfx, ect.) would probably go a long way as well. Prehaps as the bullets get heavier a small knockback could be applied to the character on firing?
Overall this is a really great little game, and I had a lot of fun playing it. Well done!