Well done game! I hope the jam has been a positive experience for you despite three panic attacks!
For a long while I felt overpowered with a single fire rate upgrade, then suddenly I was being overwhelmed and had to spam upgrades in the pause screen! :D I like how the turret's three cannons are animated and the effect of hitting the incoming ships a lot.
The one thing I'd say is the music gets drowned out by the gunfire, especially when it starts shooting faster.