On the game page itself. If you scroll down to the download button, you'll see "more information". If you fold that open, you can see the star rating. I believe that's where you can rate the game. π
I've uploaded the latest version where you can go to the options menu and turn off the passenger.
You can unlock the motorcycle if you win the game with one of the two first cars and then win the game with the Countach.
I don't know why, but I don't get notificaties if I get a reply. So excuse me if I don't answer immediately. I've read your suggestion to add music during the menu. Do you have any suggestions which music should be played? π