Good game, but there are a couple of things I would do to help it be a great one!
1. Feedback on getting hit could be clearer. You do flash, but a tenth of a second screen flash and a sound effect would really help seal the deal.
2. Since you flash from getting hit (but aren't dead), I thought the same about the enemies when they flash. As a result, I ended up unloading on enemies until about my third play through. Maybe a sprite where they end up lying on the ground would help with the visual inconsistency there.
3. I think if you could see farther ahead, it would help gameplay. I'm not sure how it actually works, but it felt like I was getting sniped by enemies right before I could actually see them. If you have the camera follow the player so that he ends up on one of the third lines, it could look even more cinematic while also helping with visibility.
Overall the game was quite fun (especially the visuals) and I can tell you had fun making it!