Having bigger size mean faster move speed was clever; it made for an interesting balancing act, especially with the somewhat slow size changing -- i.e. trying to get as big as possible between obstacles while scaling down soon enough that you actually clear the gaps.
Music was great and really added a lot of the tension. I would have liked to see even more of that tension building by e.g. making the music more intense the closer the killer is to you. I also liked the added mechanics of the button/door (and making the player have to stand there and wait for it to open was a great call) and the gates that opened and closed by themselves. It would have been cool to have a few more implementations of those, or new ones.
Ran into a bug with the gates that open and close, where if I get hit by them on the way down, I just get stuck in there and can't really scale anymore (I just sort of vibrate in place).