Sid Meier's Alpha Centauri (sometimes abbreviated to SMAC or 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.