Excellent level design! I appreciate how you carefully lead players through the first level to teach them basic mechanics and explain things. The idea is very interesting, because it's fun to watch the objects soaring through the air as you rewind them. Although, when they just lying down the first few seconds after the player hit "R", it feels like the rewind's not working.  Maybe you could show a progress bar, for example, to show that the rewind is actually in progress, even if the object is not moving. Nevertheless, good job! 

Very interesting. It reminded me a lot of Portal, I assume that's what you were going for?

You are absolutely right, it is super short: definitely could have used a few more levels. Also, I didn't understand at first that you needed to face the object you want to rewind in order to do it... or at least it seems so! Some information about this in the tutorial would be nice. But it was nice that the object being rewinded glew yellow. Also, the physics were a bit weird! I clipped through the platform in the main level a lot more times than I would like, and I had to repeat the puzzle a lot of times because I could never climb on top of the small platform without falling.

Overall, though, it's a nice idea that could be explored further!