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Street Fighter II: The World Warrior is a competitive fighting game developed by Capcom and originally released for arcades in 1991. It is the second installment in the Street Fighter series and the sequel to Street Fighter, released in 1987. It is Capcom's fourteenth game to use the CP System arcade system board. Street Fighter II improved many of the concepts introduced in the first game, including the use of special command-based moves, combo system, six-button configuration, and wider selection of playable characters, each with unique fighting style. It prominently features a popular two-player mode that obligates direct, human-to-human competitive play which prolonged the survival of the declining video game arcade business market by stimulating business and driving the fighter genre. It inspired grassroots tournament events, culminating into Evolution Championship Series (EVO). Street Fighter II shifted the arcade competitive dynamic from high score into human competition, including large groups.

Street Fighter II became the best-selling game since the golden age of arcade video games. By 1994, it had been played by at least 25 million people in the United States alone. Due to its major success, a series of updated versions has additional features and characters. Worldwide, more than 200,000 arcade cabinets and 15 million software units of all versions of Street Fighter II have been sold, grossing an estimated $10 billion in total revenue, making it one of the top three highest-grossing video games of all time as of 2017 and the best-selling fighting game until 2019. More than 6.3 million Super NES cartridges of Street Fighter II have been sold, making it Capcom's best-selling single software game for the next two decades and its best-selling game on a single platform. Street Fighter II is regarded as one of the greatest video games of all time and the most important and influential fighting game ever made. Its launch is seen as a revolutionary moment within its genre, credited with popularizing the fighting genre during the 1990s and inspiring other producers to create their own fighting series. It sparked a renaissance for the arcade video game industry and impacted competitive video gaming and wider popular culture such as films and music.