Sid Meier's Civilization is a turn-based 4X strategy game developed and published by MicroProse for MS-DOS in 1991. Designed by Sid Meier, it is the first game in the long-running series of the same name and the first game to popularize the 4X (explore, expand, exploit, and exterminate) sub-genre of strategy games. Players take on the role of a ruler of a civilization (loosely based on real-life historical civilizations) and is challenged to build it up amongst other empires (from two to six), from the end of the prehistoric era to the technological future. Over the years, the game received ports to the Mac, Amiga, Atari ST, Super Nintendo Entertainment System (published by Koei in the United States and by Asmik Ace in Japan), PlayStation (published in Japan only by Asmik Ace), and N-Gage. A special port for the Windows, titled Sid Meier's CivNet, was released in 1995, featuring online multiplayer.