Street Fighter II: The World Warrior[a] 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. 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. The leader of the Shadaloo organization, M. Bison, in his global domination plan sets up a world fighting tournament, to select the best fighters to work in his Shadaloo organization through brainwashing. M. Bison's plans are foiled by Akuma (who was not a competitor in the tournament) who catches him off guard and performs the Shun Goku Satsu on him, killing the Shadaloo boss in an instant. Akuma then takes M. Bison's place in the tournament to fight the finalist, who some sources hint is Ryu.[14] Akuma mocks M. Bison for being the slave of his own power, not knowing that he is actually in absolute control of his Psycho Power.