This is a fundamentally solid game, and I had fun with it - kudos this being your first gam jam! That storm was so smooth too, it really helped make the experience feel smoother. Some minor things I'd say to improve that could go a long way if you ever come back to this idea:
I think having some kind of small indicator of the health of each ship would especially in later stages where the visual differences between ships is not unnoticeable, but not distinct either.
I think someone said it before, but increasing the 'calm' period would also really help in the early waves.
Finally, I think some kind of meter to show when you can and can't shoot would be great. With the high initial reload times (and how it changes as you upgrade it), it would help not only with placing your shots better, but better emphasise the impact of your upgrades.
That being said, great job!