Really cool game, and interesting idea for a puzzle mechanic!
This also has the best button-pressed sounds I think I've ever heard, which is a minor detail but still worth pointing out.
I do have a few recommendations (but I'm pretty new to game-dev so take them with a grain of salt):
1. The timer should probably be paused when reading the tutorial.
2. There should probably be some kind of transition animation between levels. The lack of transition caused me to run straight into an electric fence the second a level began, since I was still pressing W when I got to the door of the last level.