Nice concept and gameplay, puzzles made total sense! But like lisyarus mentioned before, an indication of the object rewinding will definitely help. In my experience, I thought the gun wasn't working because the rewind wasn't instant. But I'm not suggesting to make it instant, I think the way it is now is important if puzzle required the player to change positions, like the last level.
Other than that, the gameplay loop is complete, it would be easy to make improvements and additions, so good job!