A nice callback to the retro games of this genre.
I think, like someone else has mentioned, the enemy density is a bit much. Also, whatever is spawning the enemies is a bit off, because if you move to the far right, nothing ever hits you.
Also, the red missile stuff seems to stop spawning after a while? And it might just be my PC, but after a while, it starts really chugging on this. A wild guess would be that the spawned enemies are never destroyed if they go past the player?