You have most of the fundamentals down. Here's what I'd add:
-make enemies blink red to indicate they are being damaged
-make sure player always blinks red when taking damage (sometimes he doesn't)
-give the sword a more generous hitbox
-make sure the player can brush up against walls without getting stuck
-make it so the enemies can no longer swing their hammer if they are already dead
The combat was fun (I liked the quick shock attack a lot), but the main thing it needs is to give the player more feedback when enemies are damaged.
I couldn't figure out how to get past the door with the magenta squares. I cleared out the enemies, but they just kept spawning, so I gave up. Speaking of which, the enemy spawn rates are crazy high. There was a horde of dozens of enemies in a tiny hallway at one point and I got creamed.