Driver AI in Stunt Car Racer, Commodore 64

This technical breakdown explains how the computer-controlled opponents work in the Commodore 64 game Stunt Car Racer, using game code and race simulations to reconstruct their behavior. Unlike the player’s fully modeled car, an opponent is represented mainly by its position on the track, lane, speed, and three vertically moving spring-mounted wheels. It is kept on the road, cannot be wrecked, and responds to the terrain through wheel compression: it leans on banked turns and can leave the track surface over a crest. Its suspension and starting height are governed by specific routines, while race sections can impose speed limits to help it clear jumps.

Opponent behavior depends on the player’s position and each driver’s habit settings. The computer car steers toward an aim that changes to pass, circle, block, or move aside from the player; on bends it generally targets the road’s middle. After leaving a bend ahead of the player, it may weave for 16 passes, with drivers such as Road Hog doing so more often than Hot Rod. Big Ed, Max Boost, and High Flyer can also randomly hop their front wheels. All drivers share the same engine, but the computer car receives special help: it can be towed from behind the player and can accelerate beyond its usual maximum for jumps. When cars collide, the player’s car takes the damage, while the opponent mainly loses speed. Thus, the apparent personalities arise from small habit values and different swerve frequencies, not distinct engines.