This was really really fun! I loved it. Reminded me a bit of luftrausers mixed with SNKRX which are both great games.
It did take me a little to figure out what was going on. The tutorial kindof makes it seem like if you hold boost you lose health? but later it did not seem like that's what happens. Also it was hard to tell what weapon you were going to get unless you saw the new ship fire, could have different-looking ships, and how much ammo you had left till the next ship.