Artificial intelligence, abbreviated as AI, in the Super Smash Bros. series refers to the intelligence of any computer-controlled (CPU) character (called computer players in-game) in the single-player and Versus Modes. In Versus Mode, players can preset the AI of a computer player. In Adventure Mode, All-Star Mode, and Classic Mode, players can still set it to some degree.
Artificial intelligence levels range from 1-9, with 1 being the weakest and 9 the strongest. Certain events in Melee give opponents a level of 0, which results in them not attacking at all (but still following whatever movement behaviour they would normally have).
 Training against CPUs
Players commonly fight against CPUs to train when there aren't other players around to play. This is a practise that is criticised by some, as besides even the highest level CPUs being of a lower level than a typical casual player, CPUs do things that human players never do (and will never do things that are common for human players to do), as well as having several exploitable flaws and being completely incapable of mind gaming. Training against CPUs does not adequately train one's cerebral skills (such as the ability to read and bait opponents), and it is often argued that excessive training against CPUs may cause a player to develop habits that work against CPUs but will be heavily exploited by human players.
However, training against CPUs does have its merits. CPUs can be used to effectively practise combos and chain throws, as well as spacing, punishing attacks, and other tech skill related things. CPUs can be more effective than human players in this regard, as they're always available and won't refuse a match where a player just want to practise the aforementioned things. Many top professional smashers have reported using CPUs to train, such as Nairo and Vinnie.
There is no consensus though on what level CPU is best to train against, with players mostly having their own personal opinion on what level is most effective. Some say level 1 CPUs are the best, as they won't have inhuman perfect shielding abilities and won't disrupt the player's training. Some say level 9 CPUs are the best, as they will actively try to fight the player and can punish mistakes the player makes. Some others say level 5 CPUs are the best for being a middle ground between the two extremes. Another camp maintains what level is best is dependent on what a player is trying to practise.
 Flaws in the AI
While it is notable that high level CPUs are precise with their reflexes, such as being able to power shield almost any attack, reflect projectiles with little hesitation, counterattack out of knockback the instant they can act, and land or control attacks that human players would find difficult such as Yoshi's Egg Throw and Pikachu's Volt Tackle, all three games are known for having AI that can be extremely flawed in most scenarios. There are many complaints surrounding the poor artificial intelligence of computer players in Super Smash Bros. and Super Smash Bros. Melee, though Super Smash Bros. Brawl also received attention to its flawed AI system; in all three games, particularly noteworthy and amusing AI flaws have been uploaded to YouTube, often by saying that the AI in the games is "just too good".
Examples of flawed AI in Super Smash Bros. (SSB) include:
- Level 9 CPU players which roll incredibly often compared to their later Melee and Super Smash Bros. Brawl counterparts.
- The general poor recovery abilities of CPUs - e.g., if the player jumps into a level 9 Captain Falcon's Falcon Dive, he will not attempt to recover. The same thing occurs if the player attacks any CPU character out of their up special.
- A tendency toward projectile/charge move spamming (such as a level 9 Pikachu consistently using Thunder Jolt or a level 9 Donkey Kong using Giant Punch cancels).
- When an item appears, a level 9 CPU will cease all fighting to get the item. However, they will ignore items dropped on clouds in the Yoshi's Island.
- A CPU player who picks up a throwing item when another player is below their platform will repeatedly throw the item to the ground until it disappears - even if the item is a Bob-omb, which often leads to the CPU self-destructing.
- In Hyrule Castle, a level 9 Kirby may repeatedly use Stone on the left side of the stage, causing him to slide down, resulting in a self-destruct.
- If there is a player on the right side of the Saffron City stage, CPUs will walk into the doors of the Pokémon trap.
- On Peach's Castle, if a human player stands on the bottom platform, a CPU on one of the moving platforms will run into the wall repeatedly.
- A Fox fighting a human player who runs to the edge of a stage such as Dream Land will cause Fox to follow and aim his Fire Fox off of the stage - resulting in a self-destruct.
There are several examples of flawed AI in Super Smash Bros. Melee. Most computer players will always spam their neutral attack and projectiles repeatedly (if they are at long distances between the player), and are very easily edge guarded. Certain stages are notorious for exploiting poor AI, such as Rainbow Cruise and Final Destination. Kongo Jungle is the best known stage for exploiting poor AI as it is easy to KO computer players by simply grabbing an edge, dropping from the edge as they attack, and then re-grabbing the edge. Also, on moving stages such as Icicle Mountain, the computer player will usually move up one platform at a time, which is too slow to escape the lower blast line when the stage speeds up.
The computer players in Melee also make poor use of their shields and use grabs far more often than normal attacks. Despite minimal use of their shields, CPUs are very precise with power shielding to both block attacks and reflect projectiles; CPU's will almost always perfect shield a projectile. They also have a tendency to overuse one move, such as Captain Falcon repeatedly using Falcon Dive and Raptor Boost after a forward throw, as well as Ganondorf overusing Dark Dive when a character is in front of and above him, and Zelda constantly using her down tilt to "lock" opponents.
Many computer players, especially while metal, will also self-destruct while attempting to meteor smash an opponent. When an item appears, CPUs will never pick them up, only picking them up accidentally trying to attack an opponent next to the item; additionally, they have poor concepts of knowing what items are in front of them, frequently causing them to walk into set Motion-Sensor Bombs, walking Bob-Ombs, and into hostile Poké Ball Pokémon. There is an exception to this when there are healing items, Poké Balls, Cloaking Devices, or Hammers present; CPUs will usually immediately cease all fighting against the player and will instead flee to pick up these items. They will often put themselves in harm's way while trying to do so, just to obtain said item.
Specific examples of poor AI include:
- Computer players have generally poor recovery abilities:
- They will never attempt to fight off edge guarders.
- They will only use their midair jumps and up special move to recover - never any alternate recovery methods such as side special moves, Air dodges or wall-grapples.
- CPU Fox and Falco will always aim in the same upward diagonal trajectory when recovering, even if using such a trajectory will result in them failing to make it back to the stage while a more desirable trajectory would allow them to recover successfully.
- If a CPU Jigglypuff runs out of midair jumps when recovering, it will use Sing, guaranteeing a failed recovery.
- A CPU Ness will only utilise PK Thunder when recovering if they are set to level nine, and will always aim it in the same upward diagonal trajectory. A lower level CPU Ness will fall and self destruct if their midair jump is not enough to make it back to the stage.
- Computer players have poor concept of continuous attacks:
- They never charge attacks that require button holding, including: smash attacks (with the exception of the Ice Climbers, who occasionally charge their forward smash), Shield Breaker, Hero's Bow, Skull Bash, Green Missile, Rollout, and the Super Scope, among others. Fire Breath also applies; it will never be held past the minimum length.
- They never use the second hit of Link's or Young Link's forward smash; as a result, CPUs cannot KO effectively as either character, as Link's forward smash is relatively weak when the first hit connects, while Young Link's first hit deals low, set knockback to set up the second, more powerful attack.
- A CPU Kirby under the effect of Stone will never end the transformation early. Besides allowing players to easily punish a CPU Kirby with powerful attacks, this will cause him to self destruct on some stages, if he hits a breakable platform above the lower blast line or is on a slope that ends offstage, cause him to slide down and off to the lower blast line.
- CPUs will never initiate a fast fall.
- AI have poor taunting habits. After the CPU respawns, if the player jumps for a distance while the CPU is walking toward them, the CPU may eventually taunt for no apparent reason.
- Upon KOing a character, CPUs will usually taunt, regardless of what is occurring around them.
- CPUs will never initiate a dash outside dash grabs.
- Upon returning on a Revival platform, CPUs will immediately reenter the fight again regardless of what is happening.
- CPUs will still shield attacks when invincible.
- CPUs will never sidestep intentionally; the only time they will sidestep is when they are trying to both shield and fall through a soft platform.
- A CPU Jigglypuff never uses Rollout or Rest. Strangely, a Kirby with Jigglypuff absorbed will attempt to use Rollout, but will never charge it when using it (as noted above).
- A CPU Marth and Roy will never use Counter.
- CPU Kirbys have unusual behavior dealing with Inhale. When they first use Inhale, they will constantly use it until they can copy a character. Additionally, they will heavily spam the move they copied. They will also never utilise the option to just spit a character out.
- A high level CPU Mario and Dr. Mario will often jump off the stage and attempt to use their forward aerial to edgeguard against recovering opponents, which depending on the stage, frequently leads to self destructs. CPU Captain Falcons exhibit similar behavior with their down aerial, but rarely self destruct when they do so.
- Picking up either a Hammer or a Starman will cause all the CPUs to run to the opposite side of the stage and stand there until the effect wears off; they will not use any defensive maneuvers whatsoever.
- If a CPU grabs a Warp Star, they will never change the trajectory of the attack.
- If a CPU grabs a Hammer, it will chase opponents until they reach a wall and continually jump in place even if the obstacle can be jumped over. They will also jump offstage to chase opponents that have jumped off the stage, and self destruct in the process.
- If they are next to the radius of Venusaur's earthquake or near Wobbuffet, the CPUs may shield even though they are not in the Pokemon's damage radius.
- When the player stands still on certain locations in stages, all opposing CPUs will cease all movement and action if the player is not in attack range, until the player moves or one of the aforementioned desired items appears. A notable example of this is the right edge of the middle right platform in Battlefield, which can be exploited in Cruel Melee.
- In Princess Peach's Castle, CPUs will always run to the opposite side of the castle when Banzai Bill appears. During this, the CPU will ignore opponents, and will not attack nor defend themselves unless an opponent comes near. When this does happen, it disrupts their normal behavior pattern and they will sometimes stay on the side of the castle where the Banzai Bill is and get KO'd by its explosion.
- Also, CPUs may run straight into the Banzai Bill in order to reach the other side
- In Brinstar, CPUs will always go to the hovering metallic platform in the centre when acid rises from the bottom. During this, the CPU will ignore opponents, and will not attack nor defend themselves unless an opponent comes near.
- When at a stop on Mute City and the stage is about to move again, they will not jump back on the main moving platform unless a player or item provokes them to go on it, leading to them sustaining avoidable damage when the stage moves.
- In Jungle Japes, when battling a CPU Ness, and the player does not move, Ness will try to jump over to the player, but will fall into the river and self destruct his first stock. Similar behavior occurs against level nine Yoshi on Fourside, who will air dodge into the first pit and SD.
- In Jungle Japes, if the player stands still on the right platform as a level nine CPU Fox comes off the revival platform, Fox will repeatedly jump into the river and fail to recover until he runs out of stocks or time runs out. A CPU Roy will also exhibit this behavior in this situation.
In Super Smash Bros. Brawl, the AI is generally more proficient with character recoveries (most prominently Luigi). If a human player gets an item like a Starman, rather than just trying to avoid that character, they'll also use the opportunity to attack any stragglers. When a Smash Ball appears, computer players will aggressively attack it at opportune times, while repelling anyone who tries to get it as well. Another significant change in AI from Melee is that computer players have a preference to targeting human players before other computer players.
Another new feature is that the computer's level in Training Mode can now be selected. The AI is also improved greatly, as opponents set to Attack mode will actively fight the player, rather than walking towards them and rarely throwing an attack like in previous installments.
Also, for each CPU level, the game gives a word to describe the CPU's skill level:
- Weak-3 (the default level)
Many rumors have circulated about the AI of Brawl. One claims that level 9 CPUs read button commands the player inputs, thereby allowing them to perfect shield more often. This sparked general dislike among the community, many of whom labelled the idea as "cheating". SLAPAHO tested this to see if this were true; no definitive results were returned, however, and they admitted that more experimentation and tests were needed.
Another rumor claims that there's a system in Brawl that enables AI players to "learn" from human players. All is Brawl blogger Churro Emiliano documented much of this widely for the first time in a blog post made at the end of 2008. Aside from some advanced techniques and play-styles, the AI have also been reported to "learn" to taunt a KO by crouch-spamming, and to overuse Falcon Punches after humans play several Falcon Punch free-for-alls. It is currently not confirmed if there is a learning mechanism or not.
The flaws in Brawl’s artificial intelligence are considerably lesser and less recurrent than in Melee, but they can still be potent. Computer players still tend to be easier to KO and edgeguard than the average human player, even when set at level 9, due to not utilising survival techniques such as DI and usually not fighting back when being edgeguarded. CPUs do, however, air dodge when sent flying, which provides minimal cushioning for knockback although usually not enough to save them. Computer players sometimes have difficulty avoiding certain stage hazards (most notable on Halberd), and are prone to self destructing in scrolling stages, such as the Melee Stages Rainbow Cruise and Big Blue. They have generally poor edgeguarding abilities, though unlike the previous two games, self destructing while attempting to edgeguard is very rare. And while they are better at recovering than in previous game, computer players still under utilise recoveries, such as by not making use of alternate recovery options with some characters, or always recovering in the same direction with a recovery move. A computer player (regardless of level) will also always aim for solid platforms that can be sweetspotted when recovering, even when there are "soft" platforms off the stage.
Aside from being flawed as stated above, in Free-for-alls, CPUs will target the human player even if they aren't teamed. They will also target the character that has the highest damage to earn a KO, and in doing so will not attack other CPUs, which results in them following each other in lockstep.
Specific examples of poor AI include:
- CPUs still underutilise the recoveries of several characters:
- A CPU Ness and Lucas will always hit themselves with PK Thunder in the same upward diagonal trajectory when recovering, even if using such a trajectory will result in them failing to make it back to the stage while a more desirable trajectory would allow them to recover successfully. This is especially noticeable on Final Destination, as Ness will often not make it back to the stage when using PK Thunder to recover (when recovery is possible), while a Lucas will often launch himself underneath the stage lips.
- A CPU Ike will not use Aether unless he is directly underneath a ledge. This causes him to self destruct without trying to recover, or waiting too long to use Aether and failing a recovery that was possible. CPU Snakes exhibits similar behavior using Cypher, often choosing to use it too late and self destructing.
- A CPU Yoshi will never use Egg Throw for recovery.
- A CPU Luigi will never use Luigi Cyclone for recovery.
- A CPU Meta Knight will never use Mach Tornado nor Drill Rush for recovery, and will often use Dimensional Cape to recover instead of Meta Knight's other superior recovery options.
- A CPU R.O.B. will not input any actions after using Robo Burner until it reaches the ground, grabs a ledge, or is hit by an attack.
- If an opponent jumps into a Fox or Falco using their up specials during the charge up phase of their move, they will angle the recovery horizontally and self-destruct.
- If a CPU Mr. Game & Watch uses Fire and fails to recover, he will repeatedly use Judge until the bottom blast line is crossed. While not necessarily problematic, there are instances where if a CPU Mr. Game & Watch reaches the apex of Fire and ends up short of the stage but in distance of reaching the ledge, the CPU will decide to use Judge too soon, causing him to miss the ledge and self destruct.
- When players grab the ledge, CPUs will stand still a safe distance from the ledge for some seconds before pursuing the ledge hanging player.
- If a CPU, regardless of level, is hit near the upper blast line while above an elevated platform, they'll fall straight down until reaching the ground after knockback is finished, while making no attempt to dodge or counterattack a pursuing player.
- When hit by an electric hitbox, a CPU may randomly DI up or down, more often DIing down, which can result in instances of an attack with an electric hitbox KOing them when the computer player would have survived otherwise.
- While CPUs in Melee could meteor cancel to a moderate degree, CPUs will never meteor cancel in Brawl, sustaining the meteor smash's full knockback before attempting recovery. This results in meteor smashes KOing computer players at much lower percentages than they KO human players.
- CPUs have difficulty recognising walls.
- A CPU Bowser will never hold Fire Breath past its minimum length. CPU Charizard replicate equivalent behavior with Flamethrower.
- When Snake uses his down throw near an edge on a CPU, the CPU will always roll toward the nearest edge the instant they can make a move.
- When Ganondorf uses Flame Choke on a CPU, they will never act the soonest they can.
- A low leveled Fox, Falco and Wolf will mostly self-destruct when using Landmaster, especially if the target is hanging on a ledge or so. A high level CPU will stay in place and repeatedly perform barrel rolls against opponents grabbing the ledge.
- When a CPU Luigi uses Negative Zone, he will almost always spam Fireball repeatedly, even when set to level nine.
- In the underground version of Mushroomy Kingdom, CPUs will sometimes repeatedly attack the blocks, ignoring the player even if items aren't on.
- http://www.youtube.com/watch?v=rk_EhpxKu8Q - Abusing DK's AI in training mode
- http://www.youtube.com/watch?v=71yUbTsR54E&feature=related - The majority of TAS videos by Andtgar show off abusing SSB AI while perfectly comboing.
- A video showing an AI flaw of Falco in Melee
- JetlagJad (2007-05-23). Super Smash Bros 64 - Tricking Fox's AI (video). YouTube. Retrieved on Jan 2, 2011.
- ChurroEmiliano (2008-12-31). The Wonders of Brawl's CPU Experience System (blogpost). AllIsBrawl.com. Retrieved on Jan 2, 2011. “When developing Super Smash Bros. Brawl, Sakurai integrated an experience system in which CPUs (mostly level 9/nasty) would actually learn from other players and try to mimic such strategies. This experience system is subject to all characters. / The way you and others play on your save data, the way they will intend to play, keeping several of their own ways of playing as well. You can tell a huge difference, by comparing...a new fresh save data of Brawl, to a very much used save data.”
- ChurroEmiliano (2008-12-29). The Wonders of Brawl's CPU Experience System (video). YouTube. Retrieved on Jan 2, 2011. “Churro (Snake) vs. Lvl 9 Link”
- ChurroEmiliano (2008-12-31). Falcon Punch Much? 0_0 (video). YouTube. Retrieved on Jan 2, 2011. “After having several Falcon Punch free-for-alls, the CPU wanted to fit in.”
- Hoidsa (2009-05-13). ...jerkette (video). YouTube. Retrieved on Jan 2, 2011.