Rubber band AI refers to a feature of artificial intelligence found in racing titles that is designed to prevent players from getting too far ahead of computer-controlled opponents. When done well, such AIs can maintain a consistent level of challenge from the beginning of an event to the end. However, when done poorly, it becomes evident that the game is bending its own rules in the computer's favour, either by temporarily enhancing the CPU's abilities, such as by making a CPU character drive at a faster speed than their vehicle is supposedly capable of going, or by inhibiting the abilities of the player(s)'s vehicle, or both. The term is derived from the metaphor of a rubber band connecting the player's car with an AI-controlled car; no matter how well the player performs, they cannot leave the computer players behind, because the rubber band will tighten again after being stretched, pulling the computer vehicle back up to the player. A complete description of the algorithm for rubber banding is found in US Patent 7278913, for the Nintendo GameCube game Mario Kart: Double Dash!!.
Although commonly associated with racing games such as the aforementioned Mario Kart series, similar features are also featured in both sports simulations and arcade titles, and are known to be incorrectly referred to as rubber banding due to their similarity to the racing concept. For example, in a football game, the opponent's quarterback may suddenly become un-blitzable when that team is behind by sixteen or more points. NBA Jam's "rubber banding" is notorious; if the AI team is behind, they will shove the player mercilessly and drive past them for unblockable dunks, while the player's own dunks and shots suddenly become noticeably less accurate.