Good audio, especially on the ominous voice! I didn't manage to get really far (got stuck on the part with the 'void'), unfortunately, but the character himself was pretty alright to control. The fact that you take a moment to actually start running was a bit jarring, but I got used to it fairly quickly (speaking of which, the animations for him were quite nice).
I think the amount of particles (?) was causing some weird lag- I was getting drops probably into the 20s on the bit with the spikes. I noticed it only seemed to happen when there was a lot of fog onscreen. Additionally, I wasn't entirely sure what the text on the top left (about the health/taking damage) meant, but that might be a fault on my part so I dunno.
Overall, though, I really like the atmosphere of the game! If you polish it a tad (and fix the particles lol) I think it could turn out swell as a full thing.