Good idea, but riddled with issues
The idea behind this game is good, and the control scheme seems simple enough. However, there are several flaws that I need to point out. First, the controls seem a little dodgy and can be hard to get used to. Second, the fights, especially against the boss and the shotgunners, can be difficult (or annoying at the very least) due to the lack of a respawn invulnerability (especially against the boss) and their ability to seemingly bypass cover (ducking below a stairway would make one think that they couldn't get hit with a shotgun blast, but it was a shallow stairway).
My main issue, however, is that I seemed to completely skip an area just because an enemy had knocked me back into a wall. I don't quite remember exactly where this was, but you might want to check the goal areas one each map just to make sure there aren't any quick ways to bypass entire levels.
All of that aside, this game isn't too bad, though a bit more of a story (and maybe a better description of the damage system) might benefit this game.