I like the concept a lot! Just a few comments:

• Add in-game tooltips for controls, it makes player's life so much easier :).
• If you use the prototype assets, I found it help to have the walls a different colors than the ground. Here a lot of assets are white and can make a bit confusing.
• Reduce the number of buttons (purple and red have the same behavior, sort of...)
• You have two rewind mechanisms (platform + R key), stick with one, it will be less confusing. My advice would be to keep the "R" rewind and use the pressure plate for the box interactions (currently, the blue pressure plate have two functions which can be confusing).
• I was unable to complete the third level, I think the platform are a little bit too quick. It could also be that I'm a bit too slow!

I feel that I say that a lot, but with a bit more polish you would have a great game! 

Keep up the good work!