I think the enemies should react more to your attacks, like a white flash and some shaking at least.
Imo it's over punishing to have insta death when you get cornered.
It would be really cool to have more thing to look out for while you are moving, other than the killed zombies, maybe the power ups could be on the ground instead of the spin the will thing. Imo that part felt disconnected from the main gameplay, it even has its own input system (it doesn't share keyboard input like the player does).
It would be nice to have the guy sprite be burned in a cartoony way or have a skeleton showing up after you blew up.
I think the story is missing some context, like why I'm trapped there or why are there zombies with ropes attached to them coming to attack me. That kind of stuff takes me off from the experience.
As a closing message, I must mention that for a first real project this is really good. Way better than my first projects back in the day so kudos for that. I hope you find the feedback to be useful.