Editing Civilization IV (section)

== Gameplay ==
''Civilization IV'' follows some of the [[4X|4X model]] of turn-based strategy games, a genre in which players control an [[empire]] and "explore, expand, exploit, and exterminate", by having the player attempt to lead a modest group of [[people]] from a base with initially scarce resources into a successful [[empire]] or [[civilization]].<ref name="4Xfulldefinition">For sources that go into detail about each of the four Xs, see: {{cite web |url=http://uk.guides.ign.com/guides/818084/page_2.html |title=Civilization IV: Warlords Guide |author=J. "PyroFalkon" Habib |date=17 August 2006 |publisher=[[IGN]] |url-status=dead |access-date=26 July 2008 |postscript=none |archive-url=https://web.archive.org/web/20120312080743/http://uk.guides.ign.com/guides/818084/page_2.html |archive-date=March 12, 2012 }}; {{cite web |url=http://www.sinsofasolarempire.com/Gameplay |title=Sins of a Solar Empire: Gameplay |publisher=[[Ironclad Games]] |format=ASPX |access-date=23 June 2008 |postscript=none |url-status=live |archive-url=https://web.archive.org/web/20111002025046/http://www.sinsofasolarempire.com/Gameplay |archive-date=2 October 2011 }}; {{cite web |url=http://www.mobygames.com/game-group/4x-games |title=4X Games: Group Description |publisher=[[MobyGames]] |archive-url=https://web.archive.org/web/20080618074603/http://www.mobygames.com/game-group/4x-games |archive-date=18 June 2008 |url-status=dead |access-date=23 June 2008 }}</ref><ref name="gameguru">{{cite web |url=http://www.gameguru.in/features/2013/12/best-civilization-games/ |title=5 Best Civilization Games |last=Mehta |first=Prakash |date=12 December 2013 |publisher=GameGuru |access-date=23 December 2013}}</ref> The condition for winning the game is accomplished through one of the five ways: militarily defeating all other civilizations in the game world, controlling over two-thirds of the game world's land and population, building the first spaceship in the Space Age and sending it to [[Alpha Centauri]], having the most dominant Culture ratings over other civilizations, or becoming "World Leader" through the [[United Nations]] votes.<ref name="ignreview">{{cite web |url=http://www.ign.com/articles/2005/10/21/civilization-iv-review |title=Civilization IV Review |last=Butts |first=Steve |date=21 October 2005 |publisher=[[IGN]] |page=4 |access-date=23 December 2013 |url-status=live |archive-url=https://web.archive.org/web/20140108144654/http://www.ign.com/articles/2005/10/21/civilization-iv-review |archive-date=8 January 2014 }}</ref> Additionally, there are multiple game scores for each civilization throughout the game based on the actions of each civilization and a number of different factors, allowing for a win condition based on the total of these points if the game timer runs out. The game can be played in multiple modes: as a [[single-player video game|single player]] facing against one or more [[artificial intelligence|computer-controlled opponents]], in hot seat mode, or through [[multiplayer video game|online multiplayer games]].<ref name="ignfaq">{{cite web |url=http://faqs.ign.com/articles/620/620531p1.html |title=Civilization IV Official Press Sheet |date=31 May 2005 |publisher=[[IGN]] |id=620531p1 |archive-url=https://web.archive.org/web/20090303223623/http://faqs.ign.com/articles/620/620531p1.html |archive-date=3 March 2009 |url-status=dead}}</ref>

As with other turn-based strategy video games, the player can customize the look and feel of their game world as well as the difficulty of any game AI players before the game starts. Each map space has a terrain type, such as plains, tundra, or desert, that affects the available resources players can extract from their environments and the movements of certain units through that terrain. The player is then given a total of 18 different civilizations to choose from, each with their own [[:wikt:pros and cons|pros and cons]], plus a leader avatar, an initial set of civilization technology, and any units unique to that civilization. When the game starts, however, it chooses random locations to place across a predefined square grid map. Like other [[Strategy video game|strategy games]], ''Civilization IV'' has a [[fog of war]] feature, in which unexplored territory remains darkened and territories without any units stationed on its designated square is shaded with darker colors.<ref name="gamespot">{{cite web |url=http://www.gamespot.com/reviews/civilization-iv-review/1900-6136659/ |title=Sid Meier's Civilization IV Review for PC |last=Park |first=Andrew |date=26 October 2005 |publisher=[[GameSpot]] |archive-url=https://web.archive.org/web/20111028013750/http://www.gamespot.com/pc/strategy/civilizationiv/review.html |archive-date=28 October 2011 |url-status=live |access-date=24 October 2009 |quote=If you have even a passing interest in strategy games, world history, or getting less sleep at night, you owe it to yourself to give Civilization IV a try.}}</ref>

===Units and combat===
[[File:Civilization IV Print Screen.png|thumb|upright|Example of some of the units and 3D graphics unique to ''Civilization IV'']]
Most units that the player can generate and use are military units, with certain attributes such as combat strength and movement rate particular to each military type. Each unit can gain [[experience point|experience]] through combat, which later translates into promotions that the player can use to assign military units new bonuses.<ref name="ignreview"/> Initially, most combat takes place on land, but further advancements in the game's [[technology tree]] can allow the player to build ships and planes with which to fight battles on sea and in the air. Any number of units can be stacked onto a single space and move as a group if so assigned, but the overall combat phase is resolved by one-on-one unit battles.

Combat is initiated when moving military units are moved onto the square occupied by an opposing force's military units and cities, and combat is then resolved with calculating statistics of each unit combined with some [[random number generation|random chance]].  Defeated units are removed from the game (apart from workers and settlers, which are captured by the attacking force), and any attacking units that are able to defeat the last defending military unit on a space will move to occupy that space.  If the space is occupied by a city the player may choose to occupy and capture the city as their own or [[Demolition|raze]] it. Other than combat, military units can also be assigned to fortify a specific space, perform sentry duties, destroy enemy city improvements, or explore the game world.

Non-military units include settlers who are used to found cities, workers who are used to improve space and gather resources, spies who can perform [[counterintelligence]] and [[espionage]], and religious missionaries who can be sent to convert different civilizations and cities. Also, with the Beyond the Sword expansion, new units are added such as executives, who can spread corporations to new cities. Throughout the game, players may also generate a special unit called a "Great Person". These are named after historical figures and can be used for one-time advantage boosts in various ways; examples include Great Engineers who increase overall production levels and Great Scientists who improve technology. Assigning inhabitants of cities to work as 'specialists' (scientists, engineers, artists, spies, merchants or priests), building certain wonders or discovering certain technologies can improve the rate at which Great People are generated.  Great Generals are generated when a player's forces achieve a certain number of victories, and can be used either to give a small amount of extra experience to all units trained in a city, or a very high level of experience to one unit.  However, like other units, Great People of all kinds can be attacked and killed before the players can use them.<ref name="ignfaq"/>

===Resources and buildings===
Once a city is founded, it will automatically begin extracting resources from surrounding spaces; the amount of spaces it can extract from is determined by the city's population size. The game automatically allocates the spaces a city uses and how its resources are maintained as the city grows, but the player is free to manage the city directly. This feature can be utilized to turn a part of the population into one of several specialized occupations; at the cost of having one less space from the city, these specialists increase gathering and production of the resources of their targeted specializations.

Each city can only produce one military unit or one building at a time; any additional units or buildings are placed into a [[queue area|queue]]. The rate of construction is determined by the amount of material collected from the surrounding spaces; players can also choose to speed production by sacrificing gold or population if they adopt the required governmental policy; called [[civics]]. The player can instead specialize the city towards gathering a particular resource instead of constructing additional units or buildings. Also, in order to produce some units or buildings, certain resources must be collected within the empire and connected to the empires trade network by roads or harbours (for example, horses are needed for mounted units, and iron for swords, while stone or marble increase production of certain Wonders.).

Buildings perform any number of different functions depending on building type; for example, early buildings such as granaries improve food storage to boost the city's growth and barracks produce better military units, while later buildings such as factories increase general production levels. There are also a number of unique buildings throughout the game.  Most notable are [[Wonders of the World|World Wonders]], which can be accessed through research nodes in the technology tree and construction through the worker unit. World Wonders provide advantages that are unique to each civilization, as they are limited to only one or two players.

Through buildings and specialists, each city also generates the "Culture" resource that contributes towards both the area upon which the city can influence for extracting resources and the overall civilization's cultural value. When two cities of different civilizations are adjacent to each other, the culture values of each city influences the space they can control; it is even possible that a city close to another civilization's city will join that civilization if their culture is strong enough. The high levels of culture gathering and attainment are also one of the default conditions that can be used to win the game.<ref name="ignreview"/>

===Technology, government and religion===
[[File:Civilization4-Civics.jpg|thumb|upright|A screenshot of [[government|Civics]] option menu in ''Civilization IV''<ref name="cavgames"/>]]
Once the first city has been founded, the player can select their first technology node from the game's technology tree to research, once the required number of research points have been accumulated, the technology is obtained. As with other types of technology trees, more advanced technology nodes require the research of other previous technology nodes.  The player can also select a future technology and immediately place into the game queue any technology nodes between the current technology level and the specified technology node. Technology can also determine another win condition; several endgame technology nodes are required to develop a colony ship to reach Alpha Centauri.<ref name="ignreview"/>

Within the technology tree are technology nodes relating to government civics and state religions, each with their own pros and cons. The player has the option of selecting which set of government civics or state religions that the player wants their civilization to follow, but not all civics and religions can be encompassed.

Once the player has formally met another civilization, they can perform diplomacy at any time. For example, if the two civilizations are on friendly terms, the player can ask to trade units and/or technology for gold and vice versa, or request opening of national borders in order to freely explore in the other civilization's territories. The player can also use the diplomacy menu to request help in a war against a third civilization, or formally declare war on any civilization in which they engage diplomacy.

Religion plays a much more important role in ''Civilization IV'' than in the previous installments of the franchise. Impacting many of the game's key mechanics like government civics and diplomatic relations, the game's new religious system, according to [[Firaxis Games]] producer Barry Caudill, was added to increase gameplay depth over the entire game.<ref>{{cite web|url=http://www.gamespot.com/articles/religion-demystified-in-civilization-iv/1100-6129610/|title=Religion demystified in Civilization IV|first=Andrew|last=Park|date=22 July 2005|website=gamespot.com|access-date=9 May 2018|url-status=live|archive-url=https://web.archive.org/web/20160727082624/http://www.gamespot.com/articles/religion-demystified-in-civilization-iv/1100-6129610/|archive-date=27 July 2016}}</ref> The game features seven religions (Buddhism, Christianity, Confucianism, Hinduism, Islam, Judaism, and Taoism) that are founded by the first civilization to research a certain technology which varies per religion. Religions can then be spread actively through the production of missionary units or passively through means such as trade routes. Religions may be spread to domestic and foreign cities and there is no limit to the number of religions that can be present in any single city. The player may only choose one state religion at a time and all seven offer identical advantages (e.g. cities with the state religion receive bonuses in happiness, and potentially in production, science, gold and even military unit experience points).

===Customization===
''Civilization IV'' is much more open to modification than its predecessors were. Game data and rules are stored in [[XML]] files, and a [[Software Development Kit]] was released in April 2006 to allow customization of [[game AI]]. The map editor supports [[Python (programming language)|Python]].<ref name="ignfaq"/><ref name="gamespy">{{cite web |url=http://pc.gamespy.com/pc/civilization-iv/662218p1.html |title=GameSpy: Civilization IV |last=Kosak |first=Dave 'Fargo' |date=27 October 2005 |publisher=[[GameSpy]] |pages=1–3 |id=662218 |archive-url=https://web.archive.org/web/20131206061753/http://pc.gamespy.com/pc/civilization-iv/662218p1.html |archive-date=6 December 2013 |url-status=dead |access-date=24 October 2009}}</ref>

The World Builder allows a player to either design a map from scratch or edit a preloaded template map as a starting point for a new game. The player can modify the map by placing and modifying any number of rivers, landmasses, mountains, resources, units, and cities, as well as their attributes such as Culture generation. The World Builder for ''Civilization IV'' is in-game, in contrast to previous ''Civilization'' games where the Map Editor was an external application.<ref name="firaxisdevblog">{{cite web |url=http://www.2kgames.com/civ4/blog_03.htm |title=Modding Sid Meier's Civilization IV |last=Caudill |first=Barry |date=20 September 2005 |website=[[2K Games]] |publisher=[[Take-Two Interactive]] |access-date=24 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20101202164144/http://www.2kgames.com/civ4/blog_03.htm |archive-date=2 December 2010 }}</ref>

More game attributes are stored in XML files, which can be edited with an external text editor or application. On September 20, 2005, [[Firaxis Games]] [[senior producer]] Barry Caudill stated that "[e]diting these files will allow players to tweak simple game rules and change or add content. For instance, they can add new unit or building types, change the cost of wonders, or add new civilizations. Players can also change the sounds played at certain times or edit the play list for your soundtrack."<ref name="firaxisdevblog"/>

The ''Civilization IV'' [[software development kit]] was released on April 13, 2006, to coincide with the release of the v1.61 patch. The kit allows players to view, modify, or even completely re-write the game's [[Dynamic-link library|DLL]] [[source code]], enabling the modification of the game's [[AI]] and other integral parts of the game that were previously not accessible.<ref name="civdownload">{{cite web |url=http://www.2kgames.com/civ4/downloads.htm |title=Civilization IV Downloads |website=[[2K Games]] |publisher=[[Take-Two Interactive]] |access-date=27 October 2008 |url-status=live |archive-url=https://web.archive.org/web/20080513225741/http://www.2kgames.com/civ4/downloads.htm |archive-date=13 May 2008 }}</ref>