The 4X video game genre is a subgenre of the strategy genre. The name comes from the 4 "X"'s that comprise a summary of the genre's gameplay:

Technically, it should be 4 E, but that abbreviation is already taken, and the "X" just sounds cooler.

In 4X games, you control an empire that is in competition with other empires. These "empires" can represent different clans, tribes or cultures, or even different alien races. Different empires may also have different advantages or disadvantages; some games even allow you to create customized empires on your own.

The empires will be competing over a region that could be as small as England, or as large as the Galaxy. Most members of the genre do not require that you play them on a specific piece of terrain. Instead, most of them offer a randomized map generator, typically with settings that affect the outcome (how many planets, how much water vs. land on Earth-like worlds, etc). The map almost always features some degree of Fog of War, requiring the player to devote resources to explore the map in order to discover new resources to exploit.

On whatever map the player chooses, there are territories on which you can build "cities" (whether planetary colonies, space stations, or just cities). Cities exploit the resources in the region where they are built, and can transform those resources into "buildings" (improvements to the city's efficiency), money, or units.

Units can move various distances on the map, possibly with terrain restrictions, and perform a variety of tasks — which may or may not include combat. You almost always have to produce a special type of unit that can create another city to let you expand your empire. Some games allow you to create customized units based on your technology base (see below), in addition to the default units included in the game.

Other empires work under the same restrictions as you (except when they are cheating bastards). You can talk to other empires, broker peace with them, trade with them, ally with them against a common foe, or kill them. Mostly kill them. Be careful: they will do the same to you, and they will remember what you've done to them.

Most 4X games feature a Tech Tree, though others may use Technology Levels instead; some even combine the two. Cities produce research, which is used to research new technologies. The Tech Tree is so named because you cannot research a technology until you have its prerequisites. You can't learn "Alphabet" until you've learned "Writing", for example. Technologies provide upgrades for cities, letting you better use their resources, build new units, buildings, or weapons, and so forth.

A staple of the genre, borrowed from the originator of the genre Civilization, is the "Wonder". It is a city-produced construct that only one city in the entire gameworld can produce. Whichever empire builds it first gets its benefits, and everyone else gets zilch. It generally confers a substantial benefit to the civilization that produced it, and it can only change hands if the city it is built in changes hands. More recent 4X games offer less powerful non-global "Wonders" that each empire can build, but can only be built in one of their cities. These typically provide a large bonus to a specific city.

One other staple originated by Civilization is the "goodie hut"; random local tribes/lost cargo pods/space anomalies that act as Inexplicable Treasure Chests for the first player to discover them. Of course, some of them can act as Chest Monsters, as well...

Just to make sure you can't be completely pacifist, you will usually encounter barbarian tribes (pirates/guerrillas/terrorists/angry alien fungi) that appear out of nowhere and cannot be negotiated with (although their units may be captured instead of destroyed if the player is clever).

Victory in 4X games will always be available by exterminating all or most of your opposition. However, 4X games are usually expected to offer one or more alternative victory conditions. Some allow you to pool your civilization's production in order to produce a gigantic monument, such as Civilization's UN Unity Spaceship, or Alpha Centauri's Ascent to Transcendence. If you can do that, spending all of those resources while defending your borders from people trying to stop you, you win. In some games, researching a long series of technologies (typically that do not provide any immediate benefit) causes victory. If you ally with all other (surviving) empires, then you win in some games. While all victory conditions are usually open to all players, some factions are often more suited to pursuing certain endgames than others.

Historical versions of the genre tend towards allowing Anachronism Stew, but at the direction of the player. A player's civilization might reach tanks and battleships by 1000 AD while the computer players are still in the iron age or develop genetic engineering before electricity. Futuristic versions tend to use a lot of Techno Babble in their unit/weapon/technology names and descriptions.

Gameplay is usually either real-time or turn-based. Sid Meier's Civilization is one of most famous exemplars of the latter, while probably the best-known of the former is the Age of Empires series.

Not to be confused with either a popular Australian brand of beer, the stand-in continent for Australia in Discworld, extreme pornography (XXXX) or the Foreign Exchange Market.


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    Tabletop Games 
  • As noted below, Avalon Hill's Civilization served as an inspiration for Sid Meier's video game of the same name.
  • Fantasy Flight Games brought out a board game version of Sid Meier's Civilization in 2010, designed by Kevin Wilson. The game remains mostly faithful to its PC counterpart, with production, research, combat, multiple victory conditions and a hidden map to explore, while condensing the whole experience to around 4 hours.
  • Empires of the Void is another Space 4X boardgame, though as one reviewer points out, it lacks the eXploration component because the entire map is visible from the beginning of the game.

    Video Games 

  • The board/computer game Empire that is the source of the Wopuld family's wealth in Iain Banks' The Steep Approach to Garbadale is a particularly complicated one of these. A similar game, Despot, features in his earlier novel Complicity. The author is a confirmed fan of the genre; he's gone on record saying Civilization is one of his favorite games of all time.
  • The Solar Empires series of video games in Austin Grossman's You are 4X games (among other things.) The term itself is dropped in the text.

Alternative Title(s): Four X Game