Civilization IV/Gameplay

This chapter is a guide to all Civ and Civ-related games. Therefore every guide will include this chapter. Civilization terminology is used here; see Civ:Terminology.

The goal of the game
The precise goals of the game vary from game to game, although all games employ conquest (eliminating all other players) and histographic (have the highest score after a set number of turns) methods of victory. In many games, more are employed, such as the "space race" (construct a spaceship that consists of multiple parts), "domination" (have most of the map within the reach of your cities), "regicide" (kill a specific unit), or "transcendence" (the researching of a specific technology).

As in chess, the game is divided into several phases and the ultimate goal of the game should not distract you from playing each phase correctly. Checking the king without purpose is useless in chess, as is making empty threats for no reason other than to make threats in Civ. In both games, an empty threat may or may not be effective, but for it to be truly effective it must have sound reasoning behind it, and if it does not work it must not punish the player who made the threat.

Cities
All Civilization games have cities. Alpha Centauri refers to them as "bases", but they serve exactly the same function. The primary function of a city is production. The secondary function of a city is acquiring and holding territory. By acquiring territory, you reduce your enemy's possibilities for production. Therefore, an unproductive city can still be very useful, but a productive city will almost always be more useful. The ideal city serves both functions.

Good city sites
The details of what constitutes a good city site depends on the game. For instance, in Alpha Centauri, high elevation is desirable. However, most other Civilization games have no concept of elevation. What they do share in common is that different terrain will produce different resources and have different defensive capabilities. Therefore, what makes a certain site desirable is always the same: an abundance of resources and an ability for the city to defend itself.

Resources and production
Cities always produce three resources. These are usually named food, shields, and trade. In SMAC, these are called nutrients, minerals, and energy, respectively. In Civilization III, "trade" was renamed "commerce". In Civilization II: Test of Time, the names depend on the current game being played. Regardless of their names, they always serve the same functions. For consistency, we will refer to them as food, shields, and trade.

Your cities are populated by citizens. They will work the surrounding terrain and produce goods. Each citizen may work one tile; the city tile is always worked automatically. For instance, a city with 6 citizens can work up to seven tiles: the center tile plus one tile per citizen. In most Civ games, citizens are restricted to the tiles they can work to a city radius. Citizens can also be specialists and not work tiles; this will be discussed later.

These are the three kinds of goods that your cities will produce:
 * Food - No civilization can survive without food. Surplus food will accumulate until the food box is full. When it is, another citizen will be added to the city and the food box will empty. The food box grows with the size of the city, usually at a constant rate. Each citizen requires two food per turn to survive. A citizen will never take more or less than this. If the city is not producing enough food to meet demand, this food will be taken from the food box. If the food box is empty and a citizen still must eat, a citizen starves and the population count will be reduced by one. In some Civ games, Settlers units need support in the form of food from their home city in addition to the shields they need for support. In these cases, if the food box empties and more food is needed, the most distant such unit will be disbanded. If more food is still needed after that, then a citizen will die. The population count will never be reduced by more than one per turn due to starvation.


 * In many Civ games, improvements and wonders may also affect how food is used to create new citizens. For example, many Civ games have the Granary improvement that half-empties the food box, and a wonder that gives Granaries to every friendly city.  In Civilization III, possession of the Longevity wonder will make your cities create two citizens instead of one when the food box fills.  In other cases, a new citizen may not be created when the food box is full because of the city reaching a population limit.


 * Shields - A city must procure raw materials (shields), which can then be used to build things. Your city will always be working on one of three kinds of projects:
 * Unit - Build a unit, such as a military unit or Settler.
 * Improvement - An improvement to benefit the city, or a Wonder to benefit your entire civilization or even the entire world.
 * Capitalization (in some games, Wealth) - Shields are converted to gold for the player's treasury, usually with a heavy penalty (e.g., four shields is converted to one trade unit).


 * Shields are added to the shield box (except in Capitalization). When the shield box is full, production is complete and the unit or improvement is immediately available. In most Civ games, but not Civilization III, shields are also used to support units beyond those that are deemed "free". If more shields are needed by units than are being collected in the city, then in Civilization a unit is disbanded, but in other versions the needed shields are removed from the shield box. If the box empties but more shields are still needed, one unit will randomly be disbanded. In most games, shields in the shield box can be destroyed through espionage.


 * Trade - Every civilization has some form of currency or barter system. You tax this trade, and the tax goes into at least one of three things:
 * Tax - The taxed goods become money in your pocket. You can use it to rush-build or use it as part of a trade with another civilization, or even give it as a gift.
 * Science - The taxed goods go toward improving scientific research.
 * Luxury - The taxed goods go toward entertaining the populace, keeping them happy or content.

Citizen happiness
For your cities to be productive, their citizens must be kept content. There are generally four degrees of happiness in a Civ game. From most happy to least happy, they are:
 * Happy
 * Content (normal)
 * Unhappy
 * Angry

Unhappy citizens are created from numerous sources. One of the most common is unhappiness due to overpopulation, in which new citizens from city growth are created unhappy. This is generally dependent of the difficulty setting in a game, with the highest difficulty level having its second and subsequent citizens in a city born unhappy. Other sources of unhappiness in many Civ games include having military units in the field, drafting citizens, or war weariness.

If the number of unhappy people exceeds the number of happy people in a city, the city will fall into civil disorder. Content citizens and specialists do not enter the equation. When a city is in civil disorder, no goods are produced other than food. In some games, you cannot rush-build during disorder as well. In many games, there are city improvements that are dangerous to have in a city under civil disorder, such as nuclear power plants and their risks of meltdown. Prolonged civil disorder in a city, or multiple cities under civil order, may lead the citizens to destroying certain city improvements (but never wonders), or, in the worst case, revolt, sending your government to anarchy. This is especially true of representative governments such as Democracy in many Civ games, where having two cities in civil disorder, or one city for more than one turn, will lead to a revolution.

A city may also turn some or all of its citizens to specialists. In some games, this ability is restricted to cities above a certain size. Specialists are always considered content, and do not work a tile in the city radius, but instead produce other effects. Many Civ games have at least three kinds of specialists: taxmen, which create additional gold for a player's treasury; scientists, which contribute to research; and entertainers, which create luxuries that can content unhappy citizens or turn content citizens happy.

Angry citizens usually appear only after capturing an enemy city, being loyal to their mother country. Angry citizens refuse to work for the new regime, and thus do not contribute anything to the city, and cannot be converted to a specialist, and in some games, rush-building is impossible while an angry citizen exists. Many strategies of dealing with angry citizens include starvation and the garrisoning of strong defensive troops. Sid Meier's Alpha Centauri does not have angry citizens, having Drones (unhappy citizens) serve both roles.

In many games, there is an additional incentive for having happy citizens, as, with the exception of angry citizens, there is no production bonus or penalty associated with the mood of a citizen and its association with the tile they work on. This incentive is called "We Love the King Day" (although in many cases "King" is substituted for a better title). This occurs when there are no angry or unhappy citizens, the number of happy citizens exceed that of content citizens, and the city is growing. "We Love the King Day" generally brings reduced corruption and waste to a city, and may bring forth additional production through production bonuses or the elimination of production penalties, depending on the type of government. In some games, and under representative governments, a city may even spontaneously grow in size. In a histographic game, happy citizens contribute more to the score than content citizens.

Research
Each turn of the game, you have a chance to accumulate research toward a civilization advance, often simplified to "tech". Techs will grant you new capabilities, or at least the chance to acquire them later, and can be used as a trading item. The only circumstances you will not accumulate research are if you have no cities, your research rate is at 0% and you do not employ scientists, or you have cities and a research rate but are not generating sufficient trade in any cities to put taxes into research. The technologies always follow a hierarchy, called the "tech tree". Most Civ games have one huge tech tree, but certain games (and certain scenarios therein), such as Civilization III, have multiple tech trees. All the games have extremely different tech trees, but they all share similarities. For instance, many players could not tell you the exact effects of "Electricity" for every single Civ game without looking it up (but good players will certainly know them for their favorite games). This is because the name of the tech may have little to do with its effects.

Choosing which tech to start researching is an important decision. It matters even more in the early game, as each tech usually takes many turns to research. Researching many techs early can trigger a game-lasting advantage. Whatever you do, make sure (except when at war sometimes) to keep researching down the path that your strategy is based on. You won't get very far in war against a much more advanced civilization.

Expansion phase
The first phase of any Civ game is the expansion phase. Each civilization tries to stake its claim to as much territory as it can, possibly even knocking out a rival with a "rush". The details of this will differ from game to game and from player to player. For instance, in Civilization I and II, a player might place cities as far apart as necessary to avoid overlap, four squares between cities, not including the cities themselves, being roughly optimal. In Civilization III, the same player might place cities extremely close together, with two squares between cities, or even one square in extreme situations. All games share a need to produce colonizing units as fast as practicable in the expansion phase.

Infinite City Sprawl
Infinite City Sprawl (ICS for short; "smallpox" in FreeCiv), refers to the strategy based on the concept that a player should have as many cities as possible to crank out hordes of cheap military units. In Civ1, this is marked by building many cities adjacent to other cities without so much as a space in between. This strategy was so powerful that in all other Civ games, it is illegal to place a city immediately next to another. So players started placing them with a one-square buffer zone in between. Civ2 did have some other countermeasures in place, such as having too many cities will cause unhappiness problems, but on the whole, using ICS was far more effective than not using it would be. Against a player already known to use ICS, the only real effective response was to also use ICS. Because this simplifies the game to an absurd degree and increases the tedium, many players hated ICS and players would usually forego their differences to gang up on anybody found to be using it. To this day, using ICS against human opponents in Civilization I or II is a serious breach of playing etiquette.

ICS as an "unbeatable" strategy came to an end by Alpha Centauri or Civilization III, although it can still be an effective strategy and many players will still use it, while facing much less hostility in response because the strategy is now beatable by other means.

Diplomacy and the meta-game
The term "meta-game" when applied to Civ diplomacy was possibly first proposed by Velociryx, one of the acknowledged masters of Civilization-style games. It is difficult to define this concept precisely, but it refers to idea that diplomacy is a game in itself, with its own rules and strategies, particulary in the way that three civs can interact with one another.

Warfare
No matter what you do, it's likely you'll eventually end up in a state of war with someone. Sometimes the warring parties are too far apart to actually engage in combat, and declaring war is mostly a token way of saying "I hate you". (Don't rely on that, though: sometimes they'll send in the navy or air force!)

Combat mechanics
In every game there is a way of fighting against either barbarians or other players. What determines the outcome of the battle is largely the same in every game. Each unit in any Civ game has an attack/defense/movement rating (or ADM rating), which determines its power when attacking other units, defending from other units, as well as how many spaces it can move. The ADM rating can also be subject to change due to other factors, such as the terrain it is in and whether the unit is in a fortified position.

In each turn of Civ, every unit has a chance to move to an adjacent square. Each type of terrain has its own movement cost, and the movement cost is taken out of a unit's movement rating whenever it moves. The movement ends for a unit whenever a unit's movement rating falls below zero for the turn. Movement points are replenished every turn. Most games also have a form of terrain enhancement that would reduce or eliminate movement costs for units. In some games, some forms of terrain are impassible. Also, some games may also have air units that use a fuel system, and thus must return to a form of refueling station (such as a city or airbase) after a certain number of turns. In addition to ADM ratings, many Civ games also have a hit point system, where a unit is destroyed when out of hit points.

Many Civ games also employ a system of combat experience. A regular unit may be promoted to Veteran status, and receive certain statistic bonuses. Veteran units in some games may be promoted further for more bonuses.

Nuclear warfare
All Civ games allow the possibility of nuclear war. For instance, all Civ games have nuclear warheads, and Civilization II allows spies to detonate nuclear devices. (The retrovirus Probe Team action in Sid Meier's Alpha Centauri is similar to this.) Use of a nuclear weapon usually has the following effects:
 * If aimed at a city, half of its population dies
 * If aimed at a stack of military units, the stack is completely destroyed
 * Surrounding tiles have pollution added, influencing the possibility of global warming
 * Everybody will declare war on you (except in SMAC, where this happens only if the UN charter is in effect)

Using nuclear weapons is not recommended unless you either have a lock on the game and want to finish it more quickly, or are in such a desperate losing position that it is the only thing that may turn the tide in your favor.