The default Nightmare mode was a bit too tough for me, so I played on Spooky mode and beat about 3 boss-like enemies to wrap it up. Really enjoyed it!
I thought the mechanics like holding SHIFT to slow down and charging up the INFERNO meter to attack were really interesting.
If I had to give one piece of feedback, the gameplay felt a bit repetitive after a while, so adding some variations in pacing or gameplay dynamics could make it even better.
Great work on this!