Interesting puzzle concept. Unfortunately I quickly forgot the rules :D (looks like I dont have any attention span at all).
I liked the graphics you pieced together. Walking indeed was very slow, luckily I automatically try shift for sprinting, like always. I would suggest to just give the player the sprint move speed and remove the shift-to-sprint feature as it does not provide anything gameplay-wise.
Anyway, good job finishing this in only 2 days.