Sid Meier's Alpha Centauri is a 4X turn-based strategic computer game created by Brian Reynolds and Sid Meier under the auspices of Firaxis Games in 1999. It is based on a fictional attempt by human beings to colonize a planet in the Alpha Centauri star system. It picks up where Meier and Reynolds' earlier title, Civilization II, left off. An expansion pack called Sid Meier's Alien Crossfire (aka SMACX or just SMAX) was also released. Although popular with gamers, the game never reached the heights of success of the Civilization games. Pre-patched versions of Alpha Centauri and Alien Crossfire were later bundled together in the Alpha Centauri Planetary Pack.
Within the game, the player assumes the role of one of the seven faction leaders and attempts to expand their colony and achieve victory. Players engage themselves in a race against the other factions and are free to adopt any number of strategies in pursuit of their goal. Scientific discoveries within the game determine what technologies are available to particular factions, which in turn determines what facilities and units they can build at their colony bases. Unlike Civilization and Civilization III, Alpha Centauri allows the player to fully customize units.