Gameplay

22 Civilization 4 pages in Gameplay.

• BuildingsCivilization 4's buildings add yields, happiness, health, culture, defense and specialist slots to the city that builds them, such as the Granary (60 hammers, keeps half the food after growth), the Library (90, +25% research and 2 Scientists) and the Courthouse (120, halves the city's maintenance). The base manual's early order is a Warrior, an explorer, a Worker and a Settler, then Barracks and Walls.
• CitiesA Civilization 4 city works the 21 tiles of its fat cross (a 5-by-5 square without its corners) for food, production and commerce, and grows when its food exceeds 2 per citizen. Its happiness and health limits, 6 and 3 on Chieftain and 3 and 1 on Deity at the start, decide how big it can usefully get.
• CivicsCivilization 4 has 25 civics in five categories (Government, Legal, Labor, Economy and Religion), and you run exactly one from each category at a time. New civics come with technologies, each has an upkeep in gold, and changing them usually costs turns of anarchy unless your leader is Spiritual.
• CombatCombat in Civilization 4 compares the attacker's and the defender's Strength after modifiers (terrain, fortification, city and culture defense, promotions, bonuses against unit types); equal Strength means even odds and double Strength 2 to 1, and the loser is destroyed unless it withdraws. Any number of units can share a tile, the best defender always fights, and siege units' collateral damage is the answer to the stack.
• CorporationsBeyond the Sword added seven corporations to Civilization 4 (Aluminum Co., Cereal Mills, Civilized Jewelers, Creative Constructions, Mining Inc., Sid's Sushi Co. and Standard Ethanol). Each is founded by spending a specific Great Person after the Corporation tech and one more, spreads by Corporate Executives to cities with its resources, and yields food, production, gold, culture, research or a new resource in return for maintenance.
• Difficulty LevelsCivilization 4's difficulty runs from Settler, the easiest and the tutorial level, through Noble, the default, where the AI plays under the same rules as you, up to Deity. Above Noble the AI gets discounts and free units while your cities start with less health and happiness; below it the AI is slowed down.
• DiplomacyIn Civilization 4 every AI leader holds one of five attitudes toward you (Friendly, Pleased, Cautious, Annoyed or Furious), with the reasons shown when you hover over its name, and trades techs, resources, gold, maps, cities and agreements such as Open Borders, Defensive Pacts and Permanent Alliances. Warlords added vassal states, Beyond the Sword colonies and the Apostolic Palace, and the United Nations can award a Diplomatic Victory.
• EconomyCivilization 4's economy runs on commerce, which a slider splits between research (100% at the start), gold, culture after Drama and, in Beyond the Sword, espionage; gold pays city maintenance (rising with the number of cities and their distance from the Palace), civic upkeep, unit support and inflation. Courthouses halve a city's maintenance, and trade routes, cottages and Markets raise income.
• EspionageIn Civilization 4's Beyond the Sword, espionage opens with Writing: an espionage slider and some buildings earn espionage points against each rival, passive missions such as seeing their research unlock as points build up, and spies spend points on missions like stealing technology, sabotage, poisoning water or inciting revolt. Great Spies, counterespionage and a No Espionage option complete the system.
• Game SetupA Civilization 4 game is set up by choosing a map type, a map size (Duel to Huge), a climate, a sea level, a difficulty, a game speed (Quick, Normal or Epic in the base game, with Marathon added later) and a civilization; the Custom Game screen adds rivals, teams, the starting era, victory types and options such as Beyond the Sword's Advanced Start.
• Great PeopleGreat People in Civilization 4 are powerful one-use units born in a city once it collects enough Great People points from specialists and wonders: the first costs 100 points, the second 200. The base game has five kinds (Prophet, Artist, Scientist, Merchant, Engineer); Warlords added the Great General and Beyond the Sword the Great Spy.
• MultiplayerCivilization 4 is played online through Steam (Steamworks replaced GameSpy in June 2014), on a LAN, in Hot Seat on one PC, by e-mail, and on Pitboss servers for long games; the Steamworks update removed Direct IP, which survives only in an unsupported beta branch of the original release, and Steam no longer supports the Mac version's online play.
• National Wonders and ProjectsIn Civilization 4 every civilization can build each national wonder once (Heroic Epic, National Epic, Wall Street, Oxford University and the rest), and each city can hold only two of them. Projects are big one-time builds: the Manhattan Project enables nukes for everyone, the Apollo Program unlocks the spaceship parts, the Internet grants techs and SDI intercepts nukes.
• PromotionsCivilization 4 units earn experience points (XP) by winning battles and spend them on promotions such as Combat I to V (+10% Strength each), City Raider, City Garrison, Drill, Medic and Blitz. The first promotion comes at 2 XP, then 5, 10 and 17, attacking earns twice the XP of defending, and Barracks and other buildings give new units free experience.
• ReligionsCivilization 4 has seven religions (Buddhism, Christianity, Confucianism, Hinduism, Islam, Judaism and Taoism) with identical effects; each is founded by the first civilization to discover its technology, in a Holy City that can later build the religion's shrine. Religions spread on their own and by missionaries, and a shared or rival State Religion shapes how the AI leaders treat you.
• ResourcesCivilization 4 has 35 resources in three groups: strategic resources that units and buildings need (copper, iron, horse, oil, aluminum, coal, uranium, plus stone and marble for wonders), health resources such as wheat, corn, rice and fish (+1 health each), and happiness resources such as gold, silk and wine (+1 happy each). A resource works once improved and connected by road, river or coast.
• ScenariosCivilization 4's scenarios are self-contained games with their own maps, rules and goals; the base game shipped with a few (Firaxis's Crusades and Alexander the Great among them), Warlords added eight historical and alternate-history scenarios, and Beyond the Sword added 11 scenarios and mods, from Final Frontier, Next War and Afterworld to the fan-made Rhye's and Fall of Civilizations and Fall from Heaven.
• TechnologiesCivilization 4 has 86 technologies in the base game by Firaxis's count, from Agriculture and Fishing to Fusion and Future Tech, and Beyond the Sword adds six more. Each one costs research and unlocks units, buildings, civics, religions or abilities, and the tree lets you reach most techs by more than one path.
• Terrain and ImprovementsEvery Civilization 4 tile yields food, production and commerce by its terrain (grassland 2 food, plains 1 food and 1 production, coast 1 food and 2 commerce), and Workers raise those yields with improvements such as farms, mines, cottages that grow into towns, workshops, windmills, watermills and lumbermills.
• UnitsEvery Civilization 4 unit has one Strength value, a number of moves and often bonuses against other unit types, in 11 categories from recon and melee to armored and air. Strength runs from 1 or 2 for the first units to 40 for Modern Armor and the Battleship, and Firaxis counted 89 units in the base game.
• Victory ConditionsCivilization 4 has six ways to win: Conquest (eliminate every rival), Domination (two-thirds of the land and 25% more people than any rival), Cultural (three cities with Legendary culture), Space Race (reach Alpha Centauri), Diplomatic (win the United Nations vote) and Time (the highest score when the last turn ends, usually 2050 AD).
• WondersCivilization 4's world wonders are buildings only one civilization can finish in a game. The base game's chart lists 26 of them plus seven religious shrines, from Stonehenge at 120 hammers to the Space Elevator at 2,000; Warlords added three and Beyond the Sword added five more plus the Apostolic Palace. Each adds culture and Great People points, and many lose their effect when anyone learns a set technology.

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