Hi!
I love the idea, I think it could be a very cool game with more time and polish.
The main negative point imho is that the game requires to place the tiles quickly because the car will not wait for you to start moving, but, the tile placing mechanic is not polished enough to be fast and the game is very punitive.
For instance, when selecting a tile to place it, I would expect the game to allow me to replace an existing tile (by just swapping the tile I selected and the tile already place), whereas here, I need to first remove the existing tile, then pick the one I want to place in the menu, and place it. Doesn't seem like much, but when you realize that the tile sizing and replacement is not that easy to get, well, you just end up removing a tile and the car will crash.
And when the car does crash, there's no option to keep playing on your current level, you will lose all progress, which makes the game frustrating, as building a race track is hard and you lose it on any mistake.
Such a game would be great if the tile mechanic placement was perfectly fluid and intuitive, that would make it an arcade game where you have to build a race track on the fly, as Gromit does in the gif posted by michalrajkowski below :D Or, the car could wait for the user to press a "start" button, which would leave as much time as needed to build a cool track, and then see how it goes. What I mean is, the balance between the tiles/puzzle system and the car not waiting for the player isn't good.
Let me add that, while I'm sharing an overall negative thought about your game, I still think that the idea is very cool and I would love to see what your game could be with more work! I hope you'll keep on working on it, if just a bit :)
Congratulations for your entry!