4X refers to the genre of strategy games which deal with building an empire. Depending on the setting, the empire can take a variety of forms. The most common settings are Earth or an Earth-like planet (as in Civilization), a fantasy realm (as in Master of Magic) or a galactic empire (numerous examples listed below).
Whatever the setting, these games all have four primary goals.
4X stands for the goals of :
- explore refers to the fact that the player starts out with limited knowledge of the playing area or map. This can be reflected either by large areas of the map that are completely blank, or some features may be visible with limited information (for example, the stars in Master of Orion).
- expand refers to the need for the player to expand the territory under their control. This can be by creating new settlements or expanding the area under control of existing settlements.
- exploit refers to the ability of the player's empire to use the resources within their territory, and to improve the efficiency of that usage.
- exterminate refers to the primary victory condition for this type of game: eliminate all rival civilizations. The earliest 4x games had this as the only victory condition, but in an effort to be more realistic, many games in the genre now have other victory conditions. A good example of this is in the Civilization series, where the first two releases could be won by conquering the world or by having a spaceship reach Alpha Centauri, but Civilization III has six different victory conditions.
Some argue that a fifth X can be added for eXperience.