Hey thanks a lot for trying the game.. I am soo glad you liked it & found it challenging ..
The basic concept I used was the Waypoints system..where the AI car targets them in an ascending order. It also calculates the angle between the next waypoint & AI car and turns accordingly ..it also uses raycasts to avoid colliding with other AI cars..if it ramps on the wall it automatically takes a reverse & begins its journey... pls let me know if the summary helps..will be happy to go into any concept in detail...