Certainly an interesting take on rewind and was fun drifting around! However, like other people on the comments, the cube on the mountain-ish map where you go up the forest ramp does not work and got stuck there.
For feedback: To fit the theme better, perhaps add an old-school rewinder thing toys used to have at the back so it seems you're rewinding it instead of just giving it a certain power at the beginning. Or finding a model of some vehicle with it somewhere.
For difficulty: It seems it did nothing to me when I hit the trees so perhaps the car breaking down or resetting the level after a crash so you have to think about how much power to give the car.
For clarity: Would be great to see how much power you'll get when rewinding the car. Currently, it only shows the power after release.
Overall, well done on the concept and gameplay what was there!