Great, I like all the attention to detail. The only thing I can say against it is that there's no difficulty select and the difficulty doesn't scale over time. Eventually you can get 50 hearts and the level 5 weapon and never lose them, so the enemies become trivial and it's just an easier version of Flappy Bird.
I'd say to either make multiple difficulties or scale the enemy rate/health/bullets over time, maybe even add bosses?
5 stars from me if any positive change gets made to the difficulty.