Definitely a fun game, reminds me of asteroids a bit, but this is with enemies and i really like the behaviors of different mobs, like how the green ones move away the closer you get. In my opinion, the scaling of the number of mobs is fine, i can handle it personally maybe not someone else but however, their health is way too high. I wanted to see what happens when i fill up the second bar but i couldnt do it with multiple runs. Apart from that the only thing missing is probably sound effects for collisions(not for enemy firing because it may just be too much noise).
Other things id recommend are what i see in other comments, like more power ups and such.
The game is fun, something arcade-y to get lost in, so maybe even a high score and leader board can go a long way.