I apologize for the late comment, but I just tried out your game and thought that it was pretty amazing.
I like how once the music started to kick in, it was a sign saying that the monster is probably behind me xD
As much as I like the environment and design, it got really confusing once I needed to get the last fragment. Every turn I made was a complete dead end, with the monster chasing me. Once the maze changed again, I was able to get the last one.
Another thing is I never had to use the Rewind Time mechanic (mostly because I forgot about it). I think what could be a lesson to teach the player about it is have them walk down a hallway, then have the monster appear in front of the player for the first time (which also lets them know that they're not alone in the maze). Have a text show up and say "To rewind time, press R."