The pixel art in this game is awesome and I love the player feedback! You've got good sound effects, screen shake, visual effects on damage. I also really like that the bosses are seamless in the same level.
My one piece of confusion however were with these enemies. You have great hit effects, but when they have the white projectile in front of them you can't see the hit effect. I thought I wasn't doing damage to them when they had the white projectile in front of them and was trying to hit them after they shoot. I was a little frustrated because I felt like I couldn't predict which one was shooting or that I couldn't aim at them. However I then realized you do damage to them all the time. I think if you add a health bar or make the hit effect more obvious when it's covered it'd help with these enemies. 
Awesome job!