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

  • X-Plore: Look around and find interesting things.
  • X-Pand: Build more cities/colonies/space stations on the territory you just found.
  • X-Ploit: Improve the cities/colonies/space stations through various means, making the most of the resources you have acquired.
  • X-Terminate: Use those resources to kill everyone who isn't you and take their stuff.

Technically, it should be 4 E, but 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 game-world 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.

Not to be confused with either a popular Australian brand of beer or the stand-in continent for Australia in Discworld.

Examples of 4X include:

Video Games

  • The term "4X" was coined in a review of the first installment of the Master of Orion series...
    • ...which was also followed by the fantasy-based Master of Magic.
    • Master of Orion 3 riffed off this by including "The Xs" as actual McGuffins within the game, including a semi-mythical "5th X".
  • Galactic Civilizations and its sequel, GalCiv 2.
    • Galactic Civilizations 2 in particular is known for its rather ruthless and diverse AI (which only cheats if you ask it to). It has been known to produce some Magnificent Bastard moments, where one AI empire will not declare war on you, but instead convince/bribe two (or more) other empires to do so. They tend to mock you in your moments of death (should you be killed) by revealing this fact.
      • And it doesn't even know who the player is, so it even pulls these on other AIs.
  • Reach For The Stars
  • Stars!
  • Armada 2526
  • Imperialism might be called a "3.5X": the entire map is visible at the start, but the player must build specialized units to see if there is gold in them thar hills. (Or iron, or coal, or diamonds.)
  • Sid Meiers Alpha Centauri is the spiritual "sequel" to Civilization IN SPACE!. The game's tagline is "Explore. Discover. Build. Conquer." They even managed to integrate that into the gameplay on a second level: Technologies are divided into types (Explore=scout/exploration/environmental technologies, Discover=pure science, Build=industrial technologies, Conquer=military tech) and a player can have the AI "Governor" of any given base focus on one or more tracks if he/she doesn't care for micromanaging.
  • Sins of a Solar Empire is a spacegoing Real Time Strategy game with shades of 4X.
  • Same for Rise of Nations, created when its developers realized they wanted a Real Time Civilization game.[1]) It's an RTS with a Risk Style Map, but covers a lot of the same ground.
  • Castles: Siege & Conquest is a simple, somewhat realtime 4X game in which you compete with other lords for rulership of France using guile and diplomacy after the king dies without issue. Once you claim the throne, expect even your closest allies to immedietely turn on you.
  • Ascendancy was a game that let you control your species from the individual-planet-level project to managing the entire empire of star systems. It featured no less than twenty-one species, each with a different special ability - and humans aren't one of them.
  • Egosoft's X-Universe series of games (X-BTF, X-Tension, X2: The Threat, X3: Reunion, X3: Terran Conflict) is a real time space simulation like Elite. The series' motto: "trade, fight, build, think"
  • The Dominions trilogy revolves around various entities attempting to achieve godhood through the expedient method of wiping out all competition
  • Sword of the Stars.
  • VGA Planets.
  • The King of Dragon Pass is a strange example including lots of RPG and Visual Novel elements.
  • Space Empires, a series of highly-customizable 4X games with such an extensive system of micromanagement as to make the micromanagement need in the Civ games pale in comparison.
  • Light of Altair, a welcoming, simplified indie title.
  • Aurora may be one of the most complicated space 4X games ever created. The game is more like a series of spreadsheets and drop-down lists than an actual game. Planets are generated with tectonics and ecosystems, ships must be carefully crafted with much thought put into the targeting and guidance systems as well as a whole plethora of minute details, armies and civilizations can be determined down to the individual person, needless to say this game is VERY detailed.
  • Spaceward Ho!
  • Elemental War of Magic - Master of Magic's spiritual successor.
  • Age of Wonders, another successor to Master of Magic.
  • Deadlock and it's successor Deadlock II had the aspect of different races fighting over a series of planets within a Dark Cloud', the original had only one planet, which led into it's sequal and it's storyline, having found that there was actually a series of planets further in, all formerly owned by mysterious ancient race, and the race to find the technologies and temples left behind instead of being built by the players.
  • Star Ruler is another Real Time Strategy take.
  • Shores of Hazeron is a MMO 4X played from the first person perspective.


  • The webcomic Erfworld takes a somewhat disturbing look at what living in a world based on 4X and TBS rules would be like.
    • Not quite. In Erfworld, people explicitly do not know hot to make a solvent economy other than through spoils of war. If anything, Erfworld is a look at life in a Strategy Game without any other "Xs".
  • 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 might just be a fan of the genre.
  • Twilight Imperium: Basically Master of Orion as a boardgame.
  • Age of Empires and Empire Earth is 4X made into a Real Time Strategy game.
  • Avalon Hill made a game, Civilization, on which the computer game is based, where up to 7 empires (out of 10 possible) compete from the Stone age to the Rise of the Roman Empire (or if you're one of the other civs, maybe the Greek, Egyptian, or Carthagenian Empire)
  • 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 counter-part, with production, research, combat, multiple victory conditions and a hidden map to explore, while condensing the whole experience to around 4 hours.
  1. Just to be clear, that means you can go from throwing sticks to nuclear bombers in half an hour, not that it takes 5000 years to play a game.