Createive and cute idea! I think the level can be harder.
Also, for me the transaction a bit lagging and the final level, when I first play the car does not follow the rail that I placed, restart then it become normal.
I like the Puzzle game and very cool ideas, but actually I stuck on level 6 for a long time and I just realized that you can jump higher if the box's gravity is inverted. So I am quicky solved the remaining level. I think in some level can have some better guide on this mechanics.
Overall, the idea is good and nice game!