I have issues with the game feel, in particular shooting. It's difficult to maintain fire on an enemy while it's heading towards you; you either get hurt OR have to cease fire and turn around in order to maintain enough distance. It doesn't feel particularly right at all. I'd love to see more flexibility with shooting, since it seems like there's going to be a lot of it.
It's actually something similar if not exactly the same issue I ran into with a Ludum Dare warmup I made (which you can see here
If the player is still shooting, and begins to walk the other way, he should continue shooting in that direction and walk backwards.
Feel free to have a look at that and take from it what you will. This looks great!