Cities.mp2d

Category:Rulesets
===The Primacy of Cities===
Cities are the source of all your economic output. Two keys to success in the game are: (1) Having as many cities as prudently possible and (2) Quickly growing them to be large.
=== Building New Cities ===
A city is created when Settlers or Founders do the Build City (B) command on a tile. For Settlers, this creates a city of size 1. Founders create a city of size 2. 
A city can grow to larger sizes and have many citizens working many tiles around it. Famine, war, or making population units will reduce a city's population. With the loss of its last citizen, a city becomes uninhabited Ruins. Each city on the map is labeled with its population, or size.
Cities create production, gold, national territory, and technology. Below is shown how a city's citizens extract natural resources, and how to increase city productivity.
===Working land===
Each city works terrain in a 5×5 grid around the city, minus the corners. To extract resources from a tile, you assign a citizen to work that tile from the city window. The example city on the right has all 4 of its citizens working tiles. Each active tile is labeled with an Y showing the /production/ it generates every turn. By de-selecting a tile, the player can choose another tile to work, or assign the citizen to be one of 3 types of specialists (or 6 types with the Adam Smith wonder.)
Review the terrain chart to see the output of each type of terrain tile, special resources on that tile, and improvements like roads, irrigation, or mines.
=== City Radius ===
As cities grow, they access more tiles than the 5x5 grid minus corners (21 tiles). At size 21, they access the corners (25 tiles). At size 30, they access a 7x7 grid minus 1 tile in each corner (45 tiles). Naturally, this will result in a city's vision expanding to see the new tiles it's capable of working.
city
size	tiles	note 	total tiles
1-20 	5x5 	without corners	21
21-29	5x5 	with corners 	25
30+ 	7x7 	without corners	45
=== City Centers ===
The tile on which a city is located is called the city center. City centers give free output without being worked by a citizen. In addition, the city center always produces at least one food point and at least one production point. City centers also gain whatever food bonus the terrain would have if it were irrigated. Irrigating the tile will therefore give it no bonus, except in the case of Desert Rivers. If the city has a Supermarket, the city center gets an instant +50% food bonus, which can eventually become a 100% bonus if double irrigated as Farmland.
City tiles are automatically developed with Roads and other transportation improvements such as Bridges, after you have the required tech.
You cannot begin working a tile which a neighboring city is already working, nor can you work terrain inside another nation's borders. You also can't work terrain if an enemy Land unit is standing on it: this means you can siege an enemy city by putting your units on the valuable resources of an enemy city. Most units can be ordered to pillage, which destroys tile improvements. Workers, Settlers, and Engineers could even transform the terrain to make the tile less productive, just like the Romans sowing the fields of Carthage with salt.
===Buildings and Wonders===
Cities may be enhanced with buildings, each with a different effect. Some buildings require others. Most buildings become available when you achieve certain technologies, while other technology makes buildings become obsolete.
It costs production points (shields) to construct buildings — often taking several turns. Once completed, most buildings require an upkeep of gold every turn. You can dismantle and sell a building, receiving one gold for each shield used in its construction. If a turn comes where you cannot pay the upkeep on all your buildings, some will be automatically sold. Obviously this should be avoided.
Wonders are unique structures that confer special advantages to your civilization. While buildings affect only their own city, many wonders benefit all your cities. Most Commerce units (such as Goods, Wagons, Caravans, Freight, Triremes, and Galleys) can contribute their full shield cost into the construction of a Wonder, via the Help Build Wonder command.
===Specialists===
thumb|128x128px|From left to right: Entertainer, Scientist, Tax Collector, Laborer, Merchant, FarmerA city citizen usually works the land, extracting resources from one terrain tile. But citizens can also assume a specialist role.
An Entertainer produces two luxury points for their city. A Tax Collector provides three extra gold per turn for your treasury. A Scientist adds three points to your research output. If you own the Adam Smith wonder: A Merchant provides two extra trade and one extra gold per turn. A Farmer provides one extra food per turn. A Laborer provides one extra shield (production point) per turn.
When your cities grow and produce new citizens, the game's "default governor" automatically assigns them to work the nearby terrain it deems best. You will want to inspect cities that have just grown and adjust the tile or role for which the new citizen has been placed. Alternatively, you can assign your own private Governor to each city and give him orders for what types of output to prioritize. Read in the in-game help in the city's Governor tab for more information on this.
===Civilization and its Malcontents===
City growth produces crowding and class inequality, making it difficult to maintain citizen morale. Each citizen has one of four MOODS: happy, content, unhappy, or angry. Only the first four citizens of a size 4 city are naturally content. All citizens from further growth are unhappy. This is quite serious, as even one unhappy citizen can throw a city into disorder. Cities in disorder produce no food or production surplus, no science, no taxes; only luxury production remains. Purchases of buildings or units are not allowed in such a city. Such cities are easier to incite to revolt. In a Democracy or a world where the United Nations has been built, two turns of continuous disorder in a city can even result in national anarchy.
Only citizens who work tiles can vary in their moods. Entertainers, scientists, tax collectors, and other specialists enjoy enough privilege to stay content. Thus, one way to manage an unhappy citizen is to assign him to the role of a specialist. However, if cities are ever to work more than four tiles, other means of solving the morale problem must be used. There are several ways to prevent larger cities from going into disorder.
#There are buildings and wonders that affect morale by making unhappy citizens content.
#A more interesting option is to make citizens happy. This counters the effect of unhappy citizens— a city will not fall into disorder until unhappy citizens outnumber happy ones. Citizens can be made happy by disbursing an adequate portion of your national trade into luxury. Some buildings and wonders will also create happiness.
#Martial Law is available in some governments. Military units stationed within the city impose peace, forcing some citizens to be content. The Governments chart is the reference to see the effects of Martial Law.
===Celebration and its Benefits===
Cities can enter a mode called Celebration, which means that a city's happiness, morale, and communal unity are high. Depending on your form of government, Celebration brings big benefits to productivity, resistance to incited revolts and civil war, but most importantly, population growth! These benefits may give you a major advantage over nations whose citizens are merely content. Cities must have three or more citizens before they can celebrate. A city will enter a state of celebration when half or more of its citizens are happy, and none is unhappy. The benefits of celebration vary in different governments:
Celebration Bonuses for Governments
Government 	tile bonus 		population growth bonus
Anarchy 	no penalties 		+1 food on irrigated grass/wheat/etc.
Despotism 	no penalties 		+1 food on irrigated grass/wheat/etc.
Monarchy 	+1 trade on trade tiles		--
Constitutional Monarchy	+1 trade on ocean tiles		rapture growth
Republic 	-- 		rapture growth
Democracy 	-- 		rapture growth
Theocracy 	+1 trade on trade tiles		rapture growth
Communism 	+1 trade on trade tiles		rapture growth
Nationalism 	+1 trade on ocean tiles		rapture growth
== City Growth ==
History shows that small nations can be overwhelmed by large nations. Growing a large population is key to national survival and increasing your military, industrial, and scientific output. Every leader should master how to grow cities as large as possible and as fast as prudently possible. There are three ways to grow city population. Knowing and combining all three may be important. Below, the three ways are ordered from least effective to most effective.
===Standard City Growth===
Each time a city's accumulated grain goes over the grain ceiling, the city will increase in population, the grain store will reset to 0, and the new grain ceiling will increase up to a maximum ceiling of 60. This means that as small cities grow larger, they usually grow slower. This can change later with advanced agricultural technology or Migration and Rapture growth. Nevertheless, Standard Growth is something that all nations must harness, especially in the beginning of the game. There are several ways to make your Standard Growth competitive with other nations: (1) Settle your cities (especially early cities) on high food tiles and near high food resources such as Wheat, Oasis, Fruit, Elk, etc. (2) Prioritize irrigating a new irrigable tile before the city grows and uses it. (3) Invest in Granaries and/or The Pyramids, to reduce food requirements by -50% or -25%, respectively. (4) Find ways to eliminate tile penalties on food during Despotism (The Sphinx, Chand Baori, Code of Hammurabi, Mausoleum of Mausolos, Totem Pole, Celebration, Courthouse, and last but definitely not least: exiting Despotism as fast as possible.)
Grain required to grow to city size:
target city size ⏩ 	2 	3 	4 	5 	6 	7 	8 	9 	10	11	12	13
grain needed: 	15	20	25	31	37	45	53	60	60	60	60	60
Anarchy, Despotism, and Monarchy are limited to this type of Standard Growth. This means these three governments are eventually doomed to obsolescence. All other governments can use and combine additional ways to grow their cities faster:
===Migration Growth===
Peasants, Pilgrims, Proletarians, and Migrants are known as Migration units. These are useful for growing your cities much faster. Theocracy produces Migration units which cost their original city no loss of population. All other migration units have a population cost: usually they remove 1 population from a city and put it into a unit, which can travel to another city to grow that city by +1 population. At first glance, this appears to be a zero-sum break-even in population: one city is reduced in population, while another city gains. However, a wise leader is familiar with how smaller rural towns can continuously surge the population of major cities via migration, or how some large cities are "population capped" (perhaps by lack of Sanitation tech), and can continually migrate citizens while staying at or near their "population cap ceiling." Some cities can quickly and continuously grow fast while "feeding" slower growing cities with Migration units. Migration units are especially effective when they are made in cities with:
* (1) a high food surplus, and/or
* (2) low grain requirements needed to continually and quickly replace lost population (for example, small towns with a Granary), and/or
* (3) rapture capabilities (even non-rapture governments can rapture in a single city with the Pyramids.) This is especially efficient if the city has a 'growth ceiling' due to lacking a Bank, Aqueduct, Sewer System, etc. In such cases, the city raptures up to its "population ceiling", then makes a migration unit, loses 1 population, sends the unit to a non-rapturing city to grow it, and repeats--potentially every turn.
When done optimally, migration growth transfers the fast growth rate of smaller agricultural cities, rapturing cities, and pop-capped cities, into other cities whose standard growth rates are much slower. This gets slower growing cities up to larger metropolitan size.
Only four governments can create cheap migration units to sustain migration growth strategies. Each of these governments has its own type of migration unit with various features, advantages, and disadvantages. Any government can also use Settlers as a Migration unit, though the expense of this unit limits its effectiveness to rare or special situations.
===Rapture Growth===
A city that was celebrating on the turn before, and is celebrating now, and has a current food surplus, can enter Rapture and grow by one citizen, if it meets the right conditions.
Rapture Growth is the fastest and most powerful way to grow population, but it's more expensive and more difficult. Six governments can do it: Republic, Democracy, Constitutional Monarchy, Theocracy, Communism, and Nationalism. Each of these governments has Variable Conditions which regulate how fast or how frequently rapture takes place.
Rapture growth is difficult for a leader to manage, because it requires keeping cities in a continuous celebration state. This isn't easy because the larger a city grows, the more discontented its citizens become. Consequently, preparations are often made prior to beginning a sustained period of rapture:
* preparedness to have usable tiles with food and trade ready, to sustain growth
* extra workers to keep up with tile improvement demands of rapidly growing cities
* preparedness to have certain buildings and/or wonders already in place
* financial preparedness to continuously build and buy buildings/wonders to keep citizens content (e.g., Temple, Oracle, Michelangelo's Chapel)
* preparedness to build and buy buildings/wonders which increase luxury (e.g., Marketplace, Bank, Marco Polo's Embassy)
One should generally avoid using exorbitant luxury rates to rapture, though it can occasionally be done to maximize certain opportunities. If high luxury is used to grow a city beyond the size that its infrastructure can easily appease the population, it may be straddled with maintaining that high luxury rate just to keep the citizenry out of disorder. This would cause gold income from taxes to be reduced, making you less able to buy the infrastructure needed to escape the high luxury rates. It may also reduce the research needed to unlock the aforementioned infrastructure.
=== Foreign Citizens===
When a city of another nation is conquered, one third of its citizens will "turn coat" and opportunistically convert to the conqueror's nationality. In other words, two thirds of the population still affiliate with their original nationality. This changes over time. Each turn, one citizen will assimilate to the conqueror's nationality.
Unhappy Foreign Citizens count as "unhappy about military." Among the foreign citizens present at any point in time, 45% will be unhappy if you are at war with their original nation, one of which will be immune to all "contentment effects" from Temples, wonders, etc. Unhappy foreigners are not the same as citizens unhappy about overcrowding. These citizens are unhappy about military occupation. Temples, Amphitheaters, and similar buildings will have no effect on them. Their discontent can only be neutralized by Martial Law, or by a Police Station, or by a Wonder which appeases citizens who are unhappy about military activity, or by a Wonder which cancels them out with an equal or greater number of happy citizens.
The first citizens to starve will be Foreign citizens. For a cruel leader, this may seem like a solution to foreign unhappiness. However, starvation causes lawlessness except in governments who can manage Gulag effects.
=== Variable Conditions for Rapture ===
Variable Rapture is measured on a scale from 0-100. For example:
* a city with a Variable Rapture of 0 can never rapture.
* a city with a Variable Rapture of 50 will rapture one out of every two turns
* a city with a Variable Rapture of 90 will rapture nine out of every ten turns
The main factors which influence the rate at which a city raptures are:
* form of government
* whether the city was originally founded by the nation, or was conquered
* the percentage of the citizens who are foreign
          original city       conquered city   
foreign percent⏩ 	≥30%	20%	10%	0% 	⬛ 	≥30%	20%	10%	0%
 Despotism/Monarchy	0 	0 	0 	0 	⬛ 	0 	0 	0 	0
 Const.Monarchy 	80 	80 	80 	80 	⬛ 	25 	25 	25 	60
 Republic 	90 	90 	90 	90 	⬛ 	33 	33 	33 	80
 Democracy 	25 	50 	100	100	⬛ 	25 	25 	50 	100
 Nationalism 	50 	50 	50 	100	⬛ 	33 	33 	33 	67
 Theocracy* 	40* 	40*	40*	40*	⬛ 	40* 	40*	40*	40*
 Communism 	40 	40 	40 	40 	⬛ 	40 	40 	40 	40
*a Theocratic city goes to 57.2% if it has a cathedral (4 out of 7 turns).
At turn change, rapturing cities will indicate if they raptured and when they can rapture again:
TC report,
console	City dialog
with hover-text shown over icon	Explanation
		Raptured last turn.
Will skip rapture the next 2 turn-changes
		Will not rapture this turn-change
Will rapture on the turn-change after
		Will rapture this turn-change
===Managing Growth and Happiness===
Managing morale or happiness and balancing it with taxation rates is the key engine of economic management in the game. Citizens are made happy when you provide them with luxury. For every two luxury points a city produces, one content citizen is made happy (or if there are no content workers left, one unhappy worker becomes content). Besides the luxury points produced by Entertainers, cities receive some of the trade points they produce as luxury points, proportional to the nationwide luxury rate you have set.
A thorough analysis of how Freeciv calculates happiness can be found in this article.
===Military units can cause unhappiness===
Under authoritarian regimes, military units stationed in a city can prevent unhappiness through Martial Law. However, under representative governments the effect is negative— citizens become unhappy when their city is supporting Aggressive Units. Aggressive Units are any military unit not inside your borders or not in an allied city or not inside a Fortress within three tiles of a friendly city. Field units (Cruise Missiles, Nuclear weapons, and most Bombers) cause unhappiness regardless of location. See the section on governments for the number of citizens affected by each of these factors. Foreign citizens who are unhappy that you are at war with their motherland, also fall into this category of citizens unhappy about military: that is, the game mechanics affect both classes of citizens as if they are the same class.
=== Martial Law ===
Except in Republic and Democracy, military units in the same city as citizens will automatically pacify them. This is called martial law. 
===== Martial Count =====
The Martial Count in a city represents the total power of the pacification force; that is, how many unhappy citizens will be made content by martial law. Each military unit pacifies 1 unhappy citizen, rendering that citizen content. The exception is Communism, where each military unit pacifies 2 unhappy citizens. Each government has a limit on how many military units it can use to pacify unhappy citizens.
Citizens pacified by Martial Law
 	Citizens
pacified
per unit	Maximum
martial
units	Maximum
Martial
Count
from units
Anarchy 	1	♾️	♾️
Despotism 	1	♾️	♾️
Monarchy 	1	3 	3
Constitutional Monarchy	1	1 	1
Republic 	 	 	
Democracy 	 	 	
Theocracy 	1	2 	2
Nationalism 	1	5 	5
Communism 	2	3 	6
For all governments who use martial law, a Police Station in the city will boost the Martial Count by +2. Unlike martial law governments, in representative governments, Police Stations will pacify up to 2 unhappy citizens only if they are foreign citizens or citizens unhappy about aggressively stationed military units. In dictatorial governments, Police Stations force an additional 2 unhappy citizens to be content, outside of the normal martial law count. The chart below shows the effects of Police Stations in different governments:
Pacification from Police Stations
 	Added to
Martial
Count	Pacification
of Foreigners
&
Military discontent	Forced 
Content
Anarchy 	2	 	
Despotism 	2	 	+2
Monarchy 	2	 	
Constitutional Monarchy	2	 	
Republic 	 	2	
Democracy 	 	2	
Theocracy 	2	 	
Nationalism 	2	 	+2
Communism 	2	 	+2
===Starvation and Gulag Effects===
Nothing displeases people with their leadership as much as starvation. If a city starved on the most recent change of turn, it will enter the lawless state of Famine. It will not be able to produce output. Production purchases can't be made in a lawless city. (Obviously, this makes it hard to buy a Supermarket to fix the problem.) If citizens are made content on the current turn, the city can resume output activity after the upcoming TC.
Despotism and Communism governments have "Gulag Effects." A city which has recently starved can be kept in productive order if it meets minimal martial law requirements. Martial law requirements are satisfied by Martial Count, which is the sum total of martial law units and buildings which provide martial law effects. Specifically, Martial Count is increased by Military units and Police Stations.
Martial Count needed for Gulag Effects
 	Max.
Martial
Count	size
1-19	size
20	size
30	size
40	size
50	size
60
Despotism	♾️	2	4	6	8 	10	12
Communism	8 	3	5	7	❌ 	❌ 	❌
A famished city kept in order by brutal Gulag conditions suffers losses to some output:
Output losses
output 	loss	loss %
Shields	⅑ 	11%
Gold 	⅓ 	33%
Science	ALL 	100%
=== Conquered Disorder===
Unless liberated by its original owner, a conquered city will be in disorganized mayhem on the same turn it is conquered. This state is called "Lawless." Production, purchases, and income can't take place until the city is brought into order in the following turns. Governments without martial law might need extraordinary measures to bring these cities to order, such as taxing the whole nation a higher luxury rate: effectively, a large national tax to pay the extra humanitarian costs that representative governments have when they wage war. Democratic governments and nations in a world with the United Nations should be particularly mindful, as 2 turns of disorder in the same city will cause national anarchy, unless you have the Statue of Liberty.
===Empire size can affect city happiness===
All of the above discussion assumed that cities can grow to size four without unhappiness, with the fifth citizen being the first unhappy. This limit of 4 citizens decreases as you gain more cities, simulating the difficulty of imposing order upon a large empire. Different governments can support different numbers of cities before encountering this limit for the first time; see the section on government for details.
In rare cases where empires have grown wildly beyond the number of cities where no citizens are naturally content, angry citizens will appear. Angry citizens must first be converted to unhappy before they can be made content. In all other respects, angry citizens behave as unhappy citizens.
===City Moods and State Transitions===
A city mood is recorded by the game only at a snapshot of time--on each Turn Change. This is because during your turn, you may be adjusting the tiles worked, tax rates, and specialists. This is a planning state and the information you see can be thought of as a preview for the result that will be officially recorded during the upcoming TC. A city mood as recorded on one TC can affect the behavior of a city mood on an adjacent TC. For example, rapture only happens in a city that transitions from a mood of Celebration to a mood of Celebration, as recorded on two adjacent turn changes. The four moods a city can record on any particular TC are: 
# Peace - The default mood which has no bonus nor penalty.
#Celebration - The city had half or more happy citizens and zero unhappy citizens. It will collect tile and/or rapture bonuses if it records Celebration on the next TC, depending on the form of Government.
#Disorder is a "state transition warning" given between two TCs, not a recorded TC mood. At TC, the upcoming mood will be Lawless, if not prevented. 
#*A city's current real mood will be marked in red text if the upcoming mood at TC will be Lawless.
#*Disorder is indicated on the map as one fist rising in revolt over the city graphic. 
#Lawless - A breakdown of societal functions and operations. Details:
#*Caused on the TC after Disorder, if it is not adjusted/prevented.
#*Caused when a city starves at TC: "Famine"
#*Caused by City Conquest.
#*Penalties:
#**Gold and Science income are immediately nullified in a city for the TC in which it enters the Lawless mood.
#**Gold and Science income are collected in a city on a TC in which it exits the Lawless mood.
#**Shield income and Production are nullified on all TCs that take place in a city which had Lawless as its most recently recorded mood.
#**Shield income and Production are collected on a TC entering a Lawless mood, if the TC before did not record a Lawless mood. 
#***Note the difference in timing penalties that Lawless creates for Gold and Science vs. Production and Shields. The reason for it is:
#**** If a city is in Disorder, it can buy shields to make purchases during Disorder in order to prevent an upcoming Lawless mood.
#***A city in a Lawless mood cannot make purchases until after the TC in which it exited the Lawless mood.
#***Regardless of timing mechanics, a city that enters Lawless for one turn will suffer one turn of shield loss and one turn of gold/science loss.
#*Lawlessness is indicated on the map as two fists rising in revolt over the city graphic. 
== City Improvements ==
=== Buildings that multiply science ===
* Three buildings allow you to multiply the effects of the Scientists and the total research produced by your city:
	Library
cost:60 upkeep:1
requires:Writing		University
cost:120 upkeep:3
requires:University		Research Lab
cost:120 upkeep:3
requires:Computers
In addition, wonders like the Temple of Artemis and Isaac Newton's College provide significant bonuses to science output across your nation. Copernicus' Observatory will significantly boost science in a single city. Any wonder which boosts trade will also boost your science, provided you assign some of your taxes to science. The greatest trade boosting wonder is Marco Polo's Embassy.
===Buildings allowing higher population===
	Aqueduct
cost:60 upkeep:2needs Construction
allows size 9-11		Sewer System
cost:80 upkeep:2needs Sanitation
allows size 13+
=== Buildings that make unhappy citizens content ===
	Temple
cost:30 upkeep:1needs Ceremonial Burial		Courthouse
cost:45 upkeep:1needs Code of Laws		Cathedral
cost:70 upkeep:3needs Monotheism
	Amphitheater
cost:60 upkeep:4needs Construction		Police Station
cost:50 upkeep:2needs Communism tech		
=== Buildings that multiply luxury ===
Other buildings multiply gold, luxury, shield-to-coinage rates, and the effects of your Entertainers and Tax Collectors:
	Marketplace
cost:60 upkeep:0needs Currency		Bank
cost:80 upkeep:2needs Banking		Stock Exchange
cost:120 upkeep:3needs Economics
Super Highways can influence happiness by bringing in more trade, which adds more luxury:
	Super Highways 
cost:120 upkeep:3needs Automobile
=== Wonders affecting happiness ===
* Finally, many wonders can increase happiness in uniquely different ways:
** The Sphinx,
** Oracle,
**Appian Way,
** Mausoleum of Mausolos,
** Hanging Gardens,
** Angkor Wat,
** Temple of Artemis,
** Supreme Court,
** Marco Polo's Embassy,
** Statue of Zeus,
** Roman Colosseum,
** Michelangelo's Chapel,
** Shakespeare's Theatre,
** J.S. Bach's Cathedral,
** Voyage of Darwin,
** Women's Suffrage,
** Pasteur Institute,
** Propaganda Ministry
==Pollution==
Pollution appears as rubbish and gunk on tiles around the city. 
Pollution can afflict large cities as your civilization becomes industrialized. The city window shows the percentage chance that a city will create pollution next turn. 
Causes of Pollution
Pollution may happen when a city's pollution score exceeds 20. The excess over 20 becomes the percentage chance it will generate pollution next turn. Pollution score* is the sum of two elements:
#Production Pollution - The most frequent cause of pollution is total production: shield output. The total number of shields a city produces are added to its pollution score.
#Population Pollution - Your population can also increase the chance of pollution. The technologies Industrialization, Combustion, Mass Production, and Plastics, each add 25% of the city's population size to its pollution score.
* (Pollution score can be affected by bonus modifiers. A mathematical formula for Freeciv pollution is detailed here.) 
EXAMPLE: A size-16 city with 18 production would ordinarily not produce pollution, since 18 does not exceed 20. But after Industrialization, the pollution score arrives at 18 + (25% \times 16) = 22. This exceeds 20 by 2: thus, a 2% chance of pollution each turn. (With all 4 of the population pollution techs, the score would arrive at 18 + (100% \times 16) = 34. This exceeds 20 by 14, giving a 14% chance of pollution each turn.)
Cleaning and Preventing Pollution
A polluted tile can be cleaned by sending Workers, Settlers, Proletarians, or Engineers to clean pollution. This takes 2 worker-turns to complete. Polluted tiles suffer a 50% penalty on food, production, and trade.
When an unused tile becomes polluted, there is the temptation to avoid the effort of cleaning it; but the spread of pollution can accumulate an ever larger "environmental debt" that is progressively more difficult to clear.
Besides cleaning pollution, you can proactively prevent it. Environmentalism tech reduces population pollution by 50%. Buildings and wonders can also reduce pollution:
=== Buildings that reduce pollution ===
	Hydro Plant
cost:175 upkeep:2requires:Electronics		Mass Transit
cost:60 upkeep:0requires:Mass Production		Recycling Center
cost:70 upkeep:1requires:Recycling
	Solar Plant
cost:150 upkeep:-3requires:Environmentalism		Wind Plant
cost:60 upkeep:-3requires:Environmentalism		Fusion Reactor
cost:700 upkeep:0requires:Fusion Power
==Destroyed Cities==
Destroyed cities leave Ruins marking the location of the now uninhabited city. Besides marking the spot of a former habitation, old walls, buildings, cellars, and sewers provide several other features to the terrain:
*Hideouts will never disappear if built on Ruins, even if unoccupied.
*Ruins act almost like a type of Base. On Ruins, there is no Stack-Kill: i.e., units killed in Ruins die one at a time instead of all at once.
==City Output Sequence==
MP2-Dragoon uses "WYSIWYG" processing. (server setting city_output_sequence=1.)
City output is reckoned in a sequential order:
👉🏻 Each Player is reckoned one at a time in a random order.
* 👉🏻 For each Player, each city is reckoned one at a time in a random order.
**👉🏻 Then for each City, output is reckoned in a specific order.
NOTE: A newly completed Wonder's effects will only influence the city it was built in, and the cities reckoned after the city it was built in.
The reckoning sequence inside each city is ordered as follows.
#Food output accumulates.
##Food output calculated = Total food produced from tiles and bonuses.
##Food surplus calculated = Food output - 2 Food per citizen - Food upkeep (for Settlers and Migrant-types).
##Food surplus is recorded for use in step 9.1
##
#Production output (shields) accumulates, if the most recent city mood was not Lawless or Famine.
#Production completes: Buildings, Units, Wonders, Coinage.
#*Global effects from anything produced take place from this point onward.
#* 👉🏻 Step 4 through step 9 will get any bonuses or penalties from whatever was produced.
#Trade output accumulates (from worked tiles, Trade Routes, etc.)
#Gold, Science, Luxury accumulate: (Specialists + Tax rates × Trade points) × bonus factors of Buildings and Wonders.
#*Bulbs permanently assigned and credited to the technology that was researched.
#City Happiness calculated. City mood recorded for the current turn.
#Food surplus recalculation for rapture
#*The food surplus from step 1.2 is used unless production from step 3 incurs a bonus to food surplus or penalty to food upkeep.
#*If a completed production item from step 3 alters food surplus:
#*#If Settlers, Peasants, Migrants, or Proletarians were completed, then population reduced, and:
#*#*Food surplus qualification for rapture re-calculated using the Food upkeep incurred by the new Settlers, Migrants, etc.
#*#*👉🏻Thus, if you are making a food-upkeep unit and want to continue rapture, do a surplus of (1 + the food upkeep of that unit). Remember, many population units have 2 food upkeep in more advanced governments.
#*#If Harbor or Supermarket or other food-altering building was completed, then:
#*#*Food output qualification for rapture is re-calculated based on the new food effect.
#City grows by rapture if:
#* City was celebrating last turn and continued celebrating after step 6.
#*Food surplus ≥ 1   (from step 7)
#Food-based Population Change
#*Grain storage is adjusted up or down by the Food surplus recorded in step 1.3
#*If city has negative grain store, it shrinks from starvation
#*If city has grain store above the limit:
#**If there was no rapture.
#***Cities grows in size by 1
#***Grain store reset to 0 (or higher if city has Granary or nation has Pyramids.)
#****New tiles selected.
#**If there was rapture:
#***Grain store remains capped at maximum ceiling
#***Food-based growth is blocked this turn.
#Tile-Worker units who are irrigating, mining, or building roads, finish their tasks.
#*(Tile improvements finished at TC only give a bonus at the next TC, not simultaneously.)
==City Build Slots ==
Generally, a city can complete a maximum of one production item per turn. However, historically, civilizations could muster the capacity to manifest multiple units simultaneously, such as in recruiting extra foot soldiers for upcoming wars. In MP2 rules, Conscription enables this feature across your nation. In a single city, it's also enabled by the wonders Magna Carta and King Richard's Crusade. 
For a city to make multiple units per turn, 
* Your worklist must contain only units to be made. (Not buildings or wonders.) 
* The city attempting to make multiple units needs enough production (shields) to do so.
** 👉🏽 Buying the remaining shields on the first unit in queue often helps acquire enough shields. 
* The city needs buildings or wonders to provide it with extra build slots.
On a given turn, a city with extra build slots may make 1 of any kind of unit, plus extra multislot units*. For example, a city with three build slots can make 1 unit of any kind, plus two multislot units* units per turn. 
In MP2D, the following units qualify as multislot: 
* Foot Soldiers, 
* Mechanized Infantry, 
* Anti-Ballistic Missile, 
* non-nuclear Bombs, 
* Freight, 
* Peasants
The following buildings and wonders add an extra build slot to a city:
Extra City Build slots
Building 	Extra
Build
Slots	scope 	requires
Palace 	+1	city 	Conscription
Ecclesiastical Palace 	+1	city 	Conscription
Factory 	+1	city 	Conscription
Manufacturing Plant 	+1	city 	Conscription
Magna Carta 	+1	city 	Magna Carta,
Constitutional Monarchy
King Richard's Crusade	+1	city 	King Richard's Crusade
Fusion Reactor 	+1	nation	Fusion Reactor
* Multislot units are: all infantry and foot soldiers, Peasants, Anti-Ballistic Missiles, conventional Bombs, and Freight.
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