4X

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4X refers to a video game genre with four primary goals, namely to "eXplore, eXpand, eXploit, and eXterminate." The first 4X games were turn-based, but game developers have created real-time 4X games, as well.^[1][2][3] One of the best known examples of the 4X genre is Sid Meier's Civilization series, which has sold over 8 million copies.^[4]

The term "4X" was first used by Alan Emrich, in the September 1993 issue of Computer Gaming World, in the review of Master of Orion. Incidentally, Emrich was later involved in the design of Master of Orion III.^[5][6] Mainstream reviewers now use "4X" in articles about games which follow a similar pattern.^[1][7][8]

Many typical features of 4X games had appeared earlier, in board games and in 1970s computer games.

"4X" was originally an abbreviation for explore, expand, exploit, exterminate:^[6]

• Explore means the player must move units in the playing area to reveal the map. Some games begin with the map partially revealed,—for example, Master of Orion begins with stars revealed, but planets hidden—while other games begin with no initial knowledge of the map—as in the Civilization games.
• Expand means players increase the territory under their control, usually by creating new settlements, or increasing the size of existing ones. Some 4X games also incorporate the political influence of settlements, which may be extended (Civilization III and later versions; Galactic Civilizations).
• Exploit means players gather and use resources in areas they control, and improve the efficiency of that usage.
• Exterminate means attacking and eliminating rival players, pushing back their territorial expansion, and hindering their ability to exploit resources within that territory. Beyond the cost to the rival, there is often an additional tangible benefit to the attacker, such as acquired territory, loot, and resources.

These four phases overlap often in most 4X games, and some are designed so that exploration and expansion continue until quite late in the game; for example, in Master of Orion and the Space Empires series, the player must do research in order to colonize every type of planet.^[9][10]

When Emrich first used the term "4X", the vast majority of strategy games were turn-based. Dune II, the first real-time strategy game to achieve major success, was released in 1992.^[11] Many real-time strategy games such as Age of Empires or StarCraft have a similar "explore, expand, exploit, exterminate" cycle, but they are not considered 4X games. So the definition of a 4X game now requires more than having each of the four Xs.

The definition of Moby Games' "4X" category includes the requirement that it must be possible to win without exterminating all opponents. For example, in the Civilization series, it is possible to win by achievements that proves total technological and economic superiority, while in the Master of Orion series, a player may win by being elected to supreme leader of the galaxy. This criterion is explicitly meant to exclude games such as Age of Empires, WarCraft, Command & Conquer, and Heroes of Might and Magic from the 4X genre.^[7] Unfortunately this attempt to clarify the definition fails on Moby Games' own terms, because both Age of Empires and Heroes of Might and Magic offer other victory conditions. Recent developments have made the situation more complicated: Sword of the Stars and Sins of a Solar Empire are regarded as 4X games, but their only victory condition is total conquest (Sins of a Solar Empire is also entirely played in real-time).^[12][13][14]

Moby Games also attempts to distinguish 4X games by their "complex uses of diplomacy rather than the standard 'friend or foe' commonly found in non-4X strategy war games".^[7] The makers of Sins of a Solar Empire also see diverse diplomatic strategies as an important part of the 4X genre.^[15] This attempt to clarify the definition has some basis, since other definitions^[16] and several reviewers of 4X games^[17] suggest that diplomacy is a major feature of most 4X games.

Most games which are widely recognized as being of the 4X genre have most of the features described below. However, these features are not regarded as part of the genre's definition, because few 4X games offer them all, and a few non-4X games also include some of them. In particular, the " beer and pretzels" sub-genre of 4X often omits or reduces features that are common in the "full-size" instances.^[18]

4X games involve building an empire^[19] in settings such as earth,^[20] a fantasy worlds,^[21] or in space.^[22]

4X games typically provide a wider range of ways to gain the upper hand than than most other genres: trade, diplomacy —including bribery— espionage, and sabotage^{[19][23][24][14]} — even if the player's ultimate goal is total conquest.^[13] Long-term planning is vital.^[16] Hence, 4X games usually require players to use a much larger amount of information, and to manage more aspects of an empire than most other genres. Research, diplomacy, and the economy must all be constantly tended to by the player.^[14]

Each layer of gameplay can become intricate enough to resemble a minigame of its own, such as ship design in Galactic Civilizations II and Master of Orion,^[25] or tactical combat in Space Empires IV.^[23] Some 4X games even offer a separate screen display for managing battles,^[26] or a separate screen for each settlement;^[27] many also have separate screens for diplomacy with each player.^[28][29] This is in contrast to most RTS games. Dune II, which arguably established the conventions for the real-time strategy genre, was fundamentally designed to be a "flat interface," with "no additional screens."^[30]

4X games are typically complex, and include various rules.^[13] For example, Civilization IV was designed as a composite of several simple systems, which combine to create complex results.^[31].

4X games usually last longer than other strategy games. Single player games may take multiple sessions over multiple days, while multiplayer matches can take much longer.^[16] This is part of the intended design. For example, one Master of Orion II strategy guide makes it clear that in a large galaxy with a low-tech start one does not expect serious warfare before about turn 110.^[32] Even the recent real-time 4X ("RT4X") game Sins of a Solar Empire can last for over 12 hours.^[13] But a few 4X games are regarded as and aim to be "beer-and-pretzels" games that one expects to complete in a single session.^[33][34][35]

4X games have been criticized by strategy gamers for leading to excessive micromanagement, especially later in the game. "A common flaw of 4X games is its ability to quickly become overwhelming from its micromanaging. (Later in the game), expect to spend a lot of time taking care of small details." ^[36] This can detract from grand strategy by overloading the player with repetitive and mechanical work.

Some 4X games attempt to mitigate the burden of micromanagement. Most commentators agree that Galactic Civilizations succeeds, but Master of Orion III's approach has had a very mixed reception.^[37][38] The recent "RT4X" game Sins of a Solar Empire successfully reduces micromanagement without reducing the player's control of the game. ^[14]

File:Civ 3 Tech Tree Era1.png

In many 4X games research is vital, because an advanced combat unit will usually beat a larger number of less advanced units that cost more in total to produce.^[39]. In other (non-4X) games upgrades often provide only minor advantages,^[40] and the basic units sometimes remain important all the way to the end of a long game.^[41]

In some 4X games the research costs of the most advanced technologies are hundreds of times greater than those of the of the most basic technologies.^[42] Hence it is sometimes necessary to research several civilian technologies first in order to build a strong economy.^[43]

Hence 4X games typically feature a technology tree,^[44][7] and major 4X games like Civilization and Master of Orion have a much larger technology tree than most other strategy games; as an extreme example Space Empires III has over 200 technologies. Only the multi-epoch Real-time strategy (RTS) games like Age of Empires or Empire Earth can compete with typical 4X games in the number of technologies available.^[45]

4X games vary widely in the mechanisms they use to provide resources for research: in some no buildings are needed, in others research can only be done when the right buildlings are present. But in the great majority of cases the same resources are used for all types of research.^[46] For a comparison, some non-4X real-time strategy games offer some research options, usually to upgrade existing combat units. But in such games the ability to research a particular technology generally depends on having the right building, and that building can generally only research a few technologies.^[40]

The structure of technology trees varies a lot from one 4X game to another. For example Master of Orion II has one of the simplest technology trees, in which one can research all the way to the top of one technology area and neglect the rest (seldom advisable); Civilization has one of the most complex, since most technologies have two prerequisites and hence one cannot research any top-level technology without having researched almost all the lower-level technologies.^[47]

Most "4X" games allow a player to win by exterminating all rival players, or by conquering a threshold amount of the game universe. But most 4X games also offer peaceful victory conditions that involve no extermination^[7]. For example:

• Many 4X games award victory to the player in first place at the end of a time limit, or once their score reaches a certain threshold (e.g. the Space Empires series).
• The Master of Orion series lets the player leverage diplomacy to be elected supreme ruler of the galaxy.
• In Galactic Civilizations one can win by researching a supreme technology, by forging an alliance with every major civilization or by having more than 70% "influence".
• The Space Empires series awards victory for keeping the galaxy at peace for a specified number of turns.
• In the Civilization series one can win by being the first to colonize another solar system. Later in the series, one can win by becoming the planet leader (via United Nations or the Apostolic Palace in Civilization IV: Beyond the Sword) or achieving legendary culture.
• In Master of Magic one can win by researching and casting "Spell of Mastery"
• In Colonization the only way to win the game is by gaining independence. Exterminating some of the other players might be necessary to get space for expansion, but is not necessary and will not lead to automatic victory.
• In Sid Meier's Alpha Centauri victory can be achieved by building the 'Path to Transcendence' Secret Project, democratic victory (being voted in as leader of the planet), economic victory, and other methods.

Diplomacy is considered a common feature in 4X games^[16][15][17] and an element of gameplay that defines the genre.^[7] While some strategy games offer shared victory and team play, diplomatic relations are restricted to a binary choice between an ally or an enemy.^[7] 4X games often allow more complex diplomatic relations between competitors who are not on the same team.^[7] Aside from making allies and enemies, this includes the ability to trade resources and information with rival players.^[7]

In many game genres, such as Real-time strategy, First-person shooter and some Role-playing games, hands-on control of combat is a core element. But some 4X games provide little or no control over combat - the players move units into situations where they come into conflict, and combat is resolved automatically and in some games invisibly.^[48]

Even in 4X games that allow full hands-on control, the result of combat is generally determined by "what you bring to the battle" rather than by ingenious tactics.^[9]

In some 4X games a player's actions are constrained by technological and social features as well as by the actions of their opponents:

• Exploration might be limited by impassible terrain or operational ranges^[16]. Technological advances may be required to explore the full map.^[49]
• Expansion might be limited by maintenance costs and economic troubles that are more complex than a simple population limit, such as logistic concerns or corruption. Players are usually forced to consolidate and strengthen their current holdings, or discover new technologies that make their economy powerful enough to support further expansion (corruption is an important constraint in the Civilization series until Civilization IV).^[50]
• Exploitation of natural and human resources might be limited by pollution, disease, unhappiness, or civil unrest. The player often lacks the tools to overcome these limitations at the start of the game, requiring more advanced industrial or cultural developments.^[51]
• Extermination might be limited by war fatigue, morale or the activities of a peacefully-inclined political party.^[52]

Many 4X games offer options to play as one of several different races or cultures, each of which has its own advantages and disadvantages. A significant number allow the player to customize their race, and hence a player needs to decide on a strategy before play actually starts. The most extreme example may be Stars!, for which there are several very detailed articles on race design.^[53]

On the other hand racial / cultural advantages are not limited to 4X games, for example the RTS game Empire Earth has a fairly elaborate system for defining custom races.

Traditionally depth of gameplay takes priority over polished graphics and sound in 4X games.^[16]

In 2002, with the pending release of Master of Orion III, there were claims that this would be the first "5X game". Alan Emrich announced that the fifth X would be the eXperience of delegating the ruler's authority to other leaders:^{[6] [54]}

We've added a 5th X to the list (eXperience) and tried to keep a player's role in perspective. To that end, a player cannot micromanage everything all the time in MOO3. Although you can do ANYthing on a given turn, you simply won't be able to do EVERYthing during a single turn. Some things will have to wait, others you'll have to trust to the Leaders in charge of those areas. Most of the time, you'll MACROmanage a civilization's activities and try to steer the Ship of State along a general course rather than select every item for every build queue on every planet in every system of every sector that you've colonized. And with the expanded amount of playable real estate in MOO3, believe me, you'll THANK us for not forcing you to micromanage all that stuff!.^[54]

Master of Orion III received mixed comments from reviewers and players: a few liked delegating control to AI governors, while the majority found this lack of detailed control boring or frustrating.^[38]

This new "experience" also included the threat of unrest or revolt if you do not meet the demands of your citizens.^[6] However, unrest and revolt had already been seen in the 4X genre. Civilization II in 1996 included features such as civil unrest in unhappy cities, and the possibility of being over-ruled by the senate.^[55] In Galactic Civilizations, the player's party can even be voted out of office.^[52]

Some writers claim that the first 4X video games were Andromeda Conquest and Reach for the Stars (both published in 1983).^[56][57] But most fans regard Sid Meier's Civilization in 1990 as the first true 4X game, with the level of detail that has become a staple of the genre.^[14] Steve Barcia's Master of Orion from 1993 is also an early landmark in the genre, and the term "4X" was coined in a review of this game.^[6] Both had more developed technology trees and diplomatic AI.

Several earlier game genres contributed to the genesis of 4X:

• Some board games had basic elements of 4X games. For example a board game called Civilization was released in 1980 and contained elements that are common in 4X games, such as research and victory by means other than total conquest.^[58] One sign of the board game influence is the frequent mention of "rolls" (of the dice) to determine the results of actions in the manuals for Master of Orion, Master of Orion II and Civilization.
• Space opera games provided many elements seen later in space-based 4X games like Spaceward Ho! and Master of Orion. The first space opera games were text-based "Star Trek" games played in the 1970s and 1980s on mainframes and minicomputers via text-based interfaces.^[59]
• Text-based computer games about empire-building and conquest on Earth also appeared in the 1970s, for example the Classic Empire series, which has been updated to included graphics and to run on modern systems.^[60] These contributed elements to Earth-based 4X games such as the Civilization series .^[59]

By the early 1990s, the success of both Civilization and Master of Orion sparked a golden age for strategy games^[61] (especially turn-based strategy).^[62] Their respective authors produced other 4X games: Colonization (1994) was a spinoff of Civilization;^[63] but Master of Magic (1993) used a totally different economic system from Master of Orion, and the new system was also used in Master of Orion II.^[64][65] Other 4X games released in the mid 1990s include Ascendancy (1995) and Civilization II and Fragile Allegiance (both 1996) - all taking advantage of the rapidly growing processing power and graphics capabilities of PCs.

Although several 4X titles were released in the late 1990s (see the list below), the real-time strategy genre had surged in popularity. When Brett Sperry designed Dune II in 1992, he was concerned that gamers would not be interested in a real-time strategy game.^[22] But within a few years, real-time strategy games were outselling turn-based games.^[66] Total Annihilation received strong and enduring critical acclaim,^[67] and the release of the equally acclaimed StarCraft in 1998 signaled a huge success for real-time strategy games, selling 9.5 million copies over its long shelf-life.^[68] This led critics to assert that more gamers prefer real-time action to turn-based gameplay.^[66] As RTS games surged in popularity, major 4X franchises fell into difficulties. In 2001, Civilization III encountered development problems followed by a rushed release.^[69] And despite the excitement over Master of Orion III, its release in 2003 was regarded as an ambitious failure.^[38] Game publishers eventually became risk-averse to building 4X games.^[19]

Civilization IV was released at the end of 2005, garnering numerous awards from game critics.^[70] Along with Stardock's release of Galactic Civilizations 2 in early 2006, this may signal a resurgence in the 4X genre.^[71]

Ironclad Games coined the term "RT4X" to describe their game Sins of a Solar Empire (2008), which aims to blend "the 4x genre with the fast-paced and tactical elements of a real-time strategy title."^[72][73] In fact Digital Reality had been combining 4X gameplay with elements of real-time strategy to create earlier games such as Imperium Galactica in 1997 and Haegemonia: Legions of Iron in 2002.^[3]

Popular 4X games in a science fiction setting include:

• Reach for the Stars (1983)
• Anacreon (1988)
• Empire (1990)
• Spaceward, Ho! (1990)
• VGA Planets (1992)
• Master of Orion (1993), Master of Orion II (1996) and Master of Orion III (2003)
• Space Empires I-V (1993-2006)
• Iron Seed (1994)
• Stars! (1995)
• Ascendancy (1995)
• Fragile Allegiance (1996)
• Pax Imperia: Eminent Domain (1997)
• Warpath (1997)
• Imperium Galactica I (1997) and Imperium Galactica II: Alliances (2000)
• Star Wars: Rebellion (1998)
• Alpha Centauri (1999) with Alien Crossfire (1999) expansion pack
• Star Trek: Birth of the Federation (1999)
• Thousand Parsec (2001 onwards) (open source, under development)
• Haegemonia: Legions of Iron (2002) with Haegemonia: The Solon Heritage expansion pack
• Galactic Civilizations (2003) with Galactic Civilizations: Altarian Prophecy expansion pack
• Galactic Civilizations II (2006) with Galactic Civilizations II: Dark Avatar expansion pack (2006)
• Sword of the Stars (2006) with Sword of the Stars: Born of Blood expansion pack (2007)
• FreeOrion (2007) (open source)
• Lost Empire (2007) with Lost Empire: Immortals (2008) expansion pack
• Armageddon Empires (2007)
• Sins of a Solar Empire (2008)

Popular 4X games in a fantasy setting include:

• Master of Magic (1994)
• Lords of Magic (1998)
• Dominions II (2003)

Popular 4X games in a historical setting include:

• Civilization I-IV and Civilization Revolution with multiple expansion packs (1991-2008)
• Colonization (1994)
• Civilization: Call to Power (1999) and Civilization: Call to Power II (2000)
• Knights of Honor (computer game) (2004)
• Freeciv (2006)
• C-evo (2006)

• Turn-based strategy
• Real-time strategy
• Grand strategy wargame

• Build order
• Micromanagement
• Rush
• Tank rush
• Technology tree
• Turtle
• Spam