Here's my honest opinion:
-It's a cool looking pixel game!
-At first I thought there would be some hack and slash action, maybe that would be a nice addition.
-Though the rewind mechanic fits the theme very well, I find it needless to go to the lever to just return back to the start door (especially if the player forgot or choose not to pick up the gem.)
So maybe an incentive to go there would be great. Or probably redesign on how to use the rewind where it would make most sense.
I hope this helps to make it better, because you already did a good job on the rewinding and visuals.
So keep up the good work!