Like all the other people said, this one is REALLY good! i think it's the best one out of all the entries and it shows that you poured time into it.
I would suggest, if you plan on revisiting the game, adjusting the difficulty curve. Like Bobgames mentioned you have the first few cars that feel really simillar and don't teach the player much. In the end you have 4 distinct mechanics from the boss alongside the friendly helper.
I feel like you could have used the cars to introduce each mechanic on it's own and then throw them all in at the end. All together tho, amazing work I really like it :D