Rubber band AI is a video game term which describes a dynamically changing difficulty level based on the player's performance in order to maintain a constant challenge. Stated simply, the better a player does, the harder the game becomes. The term "rubber band AI" is based on the fact that computer-controlled opponents in racing games which implement this behavior seem to always catch up to the player no matter how fast the player goes, almost as if they were attached by a rubber band. Rubber band AI is most popular in racing games, but has been adopted heavily in sports and fighting games, and can be seen in various other genres as well. One of the most famous implementations of rubber band AI is in the Mario Kart series which uses it in various ways, the most obvious is how AI racers are allowed to surpass their normal maximum speed when a player is ahead of them in order to close the gap.
When rubber band AI is implemented evenly, I usually don't mind it, but when benefits the AI over the player allowing the computer to "cheat," I despise it. I almost always prefer when games have discrete difficulty levels.
Rubber band AI can be divided into two form based on whether it affects all players equally or only benefits the AI. When rubber band AI is implemented evenly, it tends to keep the game interesting by never letting the leader get too far ahead or the straggler get too far behind. In Mario Kart 64, this can be seen in the random items that are given when the player gets a question mark block. Those players in the lead with get a less-valuable item like a single banana peel or green turtle shell, while those in last place will receive very valuable items like three lightning bolts, stars, or blue shells.
When rubber band AI gives preferential treatment to the AI players, it has a negative impact on the game because players see it as unfair cheating. In Mario Kart 64, each kart has a maximum speed when a human player is driving it, but the AI is allowed to exceed the maximum speed by wide margins in order to always pose a threat to the player, regardless of the game's difficulty setting. Allowing the AI to cheat in order to make the game more difficult is an example of poor AI programming.
Here is a list of games that are important to me which utilize rubber band AI:
|Chrono Trigger||1995-03-11||The jetbike race with Johnny, is more like a rail shooter since you don't even control your acceleration, and neither the player nor Johnny can ever get very far ahead or behind. This makes it difficult to call what you're doing a "race," since using a boost just before the finish line guarantees victory, but at least it is implemented fairly. There are also items which can be acquired if the player is able to prevent Johnny from taking the lead by maneuvering around him properly.|
|Diddy Kong Racing||1997-10-21||Although it uses rubber band AI, I have found it to be far more tolerable than what is used in Mario Kart 64.|
|Left 4 Dead||2008-11-17||Left 4 Dead uses what is called the "AI director" which is just a fancy name for an algorithm which tries to balance the difficulty of the game. Essentially, if the players aren't doing so well, more healing items will be found, but if they're doing really well, uncommon infected will spawn faster. I don't mind this too much, since the game needs to have a fair amount randomness built in to keep the stages interesting, but I would have preferred set difficulty levels to make the accomplishment of victory feel more earned.|
|Left 4 Dead 2||2009-11-17||From what I've read, the AI director is much more sophisticated in this game, but also more punishing. Players who venture too far away from the pack are punished with powerful uncommon infected, players who stay in the same place for too long are punished with hordes, etc. The game has built in difficulty levels, so why mess with the difficulty dynamically?|
|Mario Kart 64||1996-12-14||I like the rubber band AI in the item randomization because it helps out weaker players, but increasing the maximum speed of AI carts far more than human players are allowed ruins the game for me. The AI speed-up is so flagrant that, even if you successfully jump the track in Rainbow Road on each lap, and E-slide the rest of the course, the AI will still catch up with you by the end.|
- youtube.com/watch?v=0JV-kMYLYCo] - Mario Kart 64 rubber band AI.
- giantbomb.com/rubber-band-ai/3015-35/games - Giant Bomb.