I first tried on normal difficulty, and most of the time I just wandered around with no enemies. Dunno if was a bug or spawn time was that low.
Problem was fixed after switching to hard mode, and the last difficulty was definitely the most fun.
My biggest problem with the game is the camera offset, almost every time I got hit was because an enemy came from the direction I was running, from which I barely can see anything.
Maybe a map or a better indication where an enemy comes from will make it much better.
Still, the game was lots of fun! Played multiple rounds of the last difficulty! Great entry!
P.S. I didn't have any noticeable framerate problems