This looks like great idea, but there is something missing to make the game interesting. It's easy to get a lot of parts at the start and then you have a car that can get easylli to the end. Also there is something wrong with the blue wheel - physics went quite crazy :D
And the problem with the game not loading up in the browser - go to project settings -> player -> in the WebGL settings find publish settings tab - the last one - and you have to switch compression format to disabled. I had the same problem...