Really nice looking game!
I have to say that sounds are a little too high for me but aside from that they match perfectly.
The movement was good but I keep being pushed on random directions by invisible forces I asume are from being hit, I think the knockback is staking somehow making the movement a little hard sometimes.
Mechanics are cool and I can see you know what you are doing when working on the guns, really sweet!
As others said there is too much happening on the screen sometimes with all the enemies and bullets, maybe you can make the player bullets and enemies bullets different or oposite colours so you can keep a better track of them.
Really fun to play and really well done! Keep the good work man! ;D