If you take a look at this site Game
then you will see that when you hit the walls or boundrys you “bounce” off them. I have accomplished stopping movement when hittest occurs but how shall I get the car to “bounce” off the walls. It would be great if you could supply the full code as I am not a great coder.
Cheers 
P.s My cars name is “car” and my boundry name is “boundry” (how original)