I was walking down the hallway and taking damage but not sure where from so I picked a direction and walked that way for a long time only to reach the end and find out that the enemies had spawned behind me and were shooting me from the other direction entirely. And since it doesn't look like they can miss / you can't see the bullets, I had to take a lot more shots on the way back.
I'm not sure if you can die or if that just lowers your score though. There were hearts and I assume they were healing me, but I'm not sure.
I would have added a sprint, made it so enemies couldn't attack from offscreen, and added a graphic for bullets. I think this has potential as a bullet hell or, if you were going for slower action, a sort of top down cover based shooter.
I like the sprite for the doors and I liked the animation on the big opening door at the end of the level.