Cooperative gameplay (often abbreviated as co-op) primarily refers to a feature in video games that allows players to work together as teammates with the absence of player-controlled competitors. Cooperative gameplay is usually built around the single player mode of a game, modified to allow additional players. Often the story is modified and the difficulty level is increased depending on the number of players in the game. Players assist other teammates in many ways: passing weapons or items, healing, and providing cover in a firefight are all advantages over single play.
Compared to competitive multiplayer, co-op gameplay has been less popular in video games, as replacing computer AI with the capability for superior human opponents has tended to take priority. Technical limitations also hindered the increased action or graphics required for simultaneous co-op play, notably on early-generation home consoles. As controller and networking technology has developed, allowing for more games to allow more than two players on PCs and consoles, cooperative games gained in popularity, especially in first-person shooters and sports games.
Since the Internet boom, PC game developers have shifted away from cooperative campaigns, instead opting to concentrate on adding competitive-based multiplayer modes for online play.
1989 saw the release of two very popular titles, Capcom's two-player cabinet, Final Fight, and Konami's Teenage Mutant Ninja Turtles, which allowed four players to fight simultaneously. Upon the release of these titles, the multiplayer beat 'em up became a very popular arcade genre. Many of these games were commercial tie-ins to existing comic book and cartoon franchises.
Though other developers would attempt to cash in on the growing craze, both Capcom and Konami would be the forerunners, producing another arcade title almost every year. Capcom followed up their success with games such as Magic Sword, Captain Commando, and Aliens vs. Predator, their final title in the genre being 1996's Dungeons & Dragons: Shadow over Mystara. Konami put out a sequel to their TMNT game, an oversized 6-player X-Men cabinet, and a 4-player beat 'em up based on The Simpsons, among others.
Though popular for several years, cooperative beat 'em ups would eventually become less popular as one-on-one fighting games such as Street Fighter II and Mortal Kombat grew in popularity. One of the last arcade beat 'em ups to be released was Sega's Zombie Revenge in 1999.
Cooperative scrolling shooters such as U.N. Squadron were also well known in arcades.
Sports games were also popular co-op games, as they were easily suited to have more than one player play together against the computer, or more often on 4-player cabinet setups for 2-on-2 play. NBA Jam was one of the most popular arcade sports titles of the early 1990s. Several WWF wrestling arcade games were also produced, as well as Capcom's Saturday Night Slam Masters. However, cooperative sports gameplay would not become more widespread until later generations of home consoles with multitaps and four controller ports became standard.
Many arcade beat 'em ups, such as Double Dragon, were ported to less advanced systems. Alternating play replaced the arcade's co-op play in the NES version (although Double Dragon II and III for the same system did retained their co-op gameplay, with the added feature of enabling or disabling friendly hits). Most other titles featuring 2-player were head-to-head sports titles. Though most of the console beat 'em ups were arcade ports, original franchises such as Streets of Rage and River City Ransom also became popular.
The run and gun genre was also popular for co-op games. Contra, for instance, was far more successful in its NES incarnation than it was in the arcade, and is famous for being one of the most popular co-op games ever, and was followed up with several sequels. Gunstar Heroes for the Sega Genesis and the Metal Slug series for the Neo Geo were also well-received titles.
Co-op games in the RPG genre have generally been less common on console systems. The 1993 action-RPG, Secret of Mana for the Super Nintendo offered two- and three-player action, once the main character had acquired his party members. Final Fantasy VI offered a form of alternating co-op play for its battles, with the second player taking control of half of the characters in the party. Namco's Tales series allowed multiple players to take control of individual members in its real-time battles in some of the titles, such as Tales of Symphonia, while the Baldur's Gate: Dark Alliance games replicated the Diablo formula for consoles, offering 4-player simultaneous play through the game's campaign.
Electronic Arts has arguably produced the most successful co-op titles in history, as their various sports franchises have been consistent best-sellers worldwide for over a decade. The original NHL Hockey and Madden NFL installments on the Sega Genesis were key games, allowing two players or more to play against the CPU. Installments of both series, among other official sports franchises developed by EA, are published annually.
Many console games support split screen displays in order to show 2 or more players in different regions of the game. Split screen displays would usually split the main screen into either 2 or 4 sub-regions so that 2-4 players could roam freely within the game world. Many first-person and third-person shooter games use this technique when played in multiplayer co-op mode, such as the console versions of games in the Rainbow Six series.
With the Nintendo 64, having four controller ports started to become a standard feature in consoles, as the Dreamcast, GameCube and Xbox all featured them. As larger multiplayer games became feasible, cooperative gameplay also became more available. The latest generation of video game consoles all feature wireless controllers, removing the past local player limits. However, its effect on multiplayer is probably less pronounced than the advancement of console internet capabilities. In most video games, co-op is an optional game mode, but in Army of Two, the entire game is co-op.
Since around the year 2000, most FPS developers have forsaken co-op campaign play, opting to focus more purely on either a more detailed and in-depth single player experience or a purely multiplayer game. Epic's Unreal Tournament series has practically eschewed single player altogether, and the most significant releases of Doom 3, Quake 4, and both Half-Life titles shipped without cooperative gameplay modes. The moddability of these titles has enabled fan-created add-ons which enable co-op play in many of these cases, though. Co-op still exists in the form of competitive teamplay, which has generally overtaken deathmatch as the dominant form of online FPS multiplayer, with titles such as Counter-Strike, Battlefield 1942 , Medal of Honor and Call of Duty gaining dominance in the early to mid-2000s.
Blizzard Entertainment's Diablo was immensely successful, largely due to being the flagship title of Blizzard's online matchmaking service, battle.net. Though local network play was an option, the game's popularity came from its internet play, allowing many players to fight through the entire single player campaign together.
Most early computer role-playing games were inspired by Dungeons & Dragons, but restricted to single player due to technical restrictions. The earliest RPGs featuring co-op were MUDs which would eventually became the MMOG genre, though it is debatable and variable if and how much these online worlds are designed around cooperative gameplay, depending on the rules of the virtual space.
Later PC RPGs became more powerful and flexible in simulating the shared real life RPG experience, allowing players to collaborate in games over the Internet. The D&D-sanctioned Baldur's Gate and Icewind Dale games allowed up to 6 players to play through the campaign mode over network.
2000's Vampire: The Masquerade - Redemption was the earliest CRPG to feature an online mode where a "storyteller" controlled a campaign much like a Dungeon Master, shaping and altering the game world against a party of human-controlled players. Atari's Neverwinter Nights was an official and comprehensive D&D simulator, featuring even more robust game-creation tools and developing a sizable online community. Besides an active modding community providing many fan-developed campaigns, the game was officially followed up with several commercial expansion packs.
A common concept in cooperative games is the sharing of resources between players. For example, two players managing one team in a real-time strategy game, such as StarCraft, will often have to draw off the same pool of resources to build and upgrade their units and buildings. The sharing of resources, however, can be as simple as the system used in the Contra games (and other shoot-'em-up/beat-'em-up games) where a player who is out of spare lives could "steal" a life from the other player so both players could continue to play at the same time.
Due to the complexity of video game coding, co-op games rarely allowed network players and local players from mixing. If there were 2 local players playing a co-op game, a network player would not be able to join that game in progress.
Some co-op games even feature a new ending when completed in co-op mode. This new ending is unlocked only when players work as a team to complete the game. This ending is sometimes customized to suit the characters which were used to complete the game. This increases the replay value of the game. Many beat 'em up games on console employ this method to increase replay value. One such game, Streets of Rage, even allowed co-op players to fight to the death at the end of the game.
Other games, such as Unreal, are modified by server administrators to restart after the single-player ending sequence; in some cases, the contents of the inventory of the players are also retained.