I loved the atmosphere and the controls were very well done. I never felt like a death was anything other than a skill issue. Platforming was a treat, I don't play many 2D platformers but this made me want to start. The steady increase in complexity and the tight level design left me wanting more and didn't overstay it's welcome! Excellent job!
Edit: Forgot to mention, I really appreciated the controller support! Something about using a gamepad made it more enjoyable