Agreed! I made most of this game in the last 24 hours which is when you should ideally be playtesting in any Game Jam. There are values to be tweaked to make the game more balanced.
Really, I ought to just make enemies take one hit to kill. However, I had the idea early on for enemies to GAIN health when getting hit with the wrong type of shot. This is implemented, but again is not obvious because there is no feedback to tell you they are actually getting more health.