Simulation Ruleset

created and maintained by Corbeau
Contact(s): forum.freeciv.org & Discord (Corbeau#1331)
This document describes the specifics of the "Simulation" ruleset branch. The first game played with this ruleset was LT42. A few other official Longturn and test games followed and, even though a lot of stuff has been balanced better and bugs and unwanted features fixed, it can still be considered relatively new, especially compared with other rulesets that were used for tens of games.
The main part of this document consists of the full description of the latest version. Changes between this and previous versions are appended at the end of the page in (very!) raw form.
For more general info, check Longturn.net , Longturn21.blogspot.com, forum.freeciv.org  and LongTurn Discord server .
A MUST-CHECK complementary resource is the Sim ruleset units table. 
= Introduction =
"Amateurs study strategy. Professionals study logistics."
The idea behind this ruleset branch is to make Freeciv game more realistic. Many decisions regarding settings were made based on how a feature should work in reality and not necessarily how it would balance the gameplay. However, Civilization games are very complex and changing one aspect doesn’t necessarily mean disbalancing it, but, rather, re-balancing, only in another configuration. At the same time, in one discussion, a nomenclature was proposed to distinguish games into “strategies” and “simulations”, where “strategies” would require greater skill and experience, while “simulations” would go for more realism and more lenient approach to unskilled players. Even though this argumentation is obviously flawed (because there are only two things that are relevant for winning a game: skill and luck, and if anything, the luck factor is seriously supressed in all civ games), I realised that “Simulation” is a good description of the idea of the ruleset and decided to name it so.
Everybody is invited to make comments about particular topics in this document, using any of the contacts listed above or, best-case, in this thread on Freciv forum.
==Ruleset goal(s)==
This ruleset was created with several goals in mind. Of course, it is always debatable if these goals were met and how much and comments and suggestions are always welcome. Development is continuing.
1. Make it real
As already stated, the main goal of the ruleset is to simulate the experience of real human history and empire management according to real-world circumstances and situations. Technically, it could be said that the main goal of any game is to be playable and fun with realism being only secondary. However, the philosophy of this project is that reality provides the most balanced and most interesting features and, when in doubt, you just have to figure out hot to transform real-world rules into a game situation to achieve the best result.
2. A nation can be defeated, but not necessarily destroyed
Another goal, completely independent and secondary to this, but, as it turned out, very compatible and going hand in hand with it, was to follow through on the Longturn's promise that you can play the game casually and still remain competitive or at least to have a fair chance of standing (at least a part of) your ground against someone who has hours to spare every day. This means that a player must be able to maintain a smaller nation and have a good chance of survival against global superpowers. 
The compatibility with the first condition is obvious. Throughout history, there have been numerous cases where this exactly happened: Netherlands vs. Spain, Japan vs. Russia (1905 war), Vietnam vs. USA (and France, and China), Afghanistan vs. USSR, Algiers vs. France, to mention only the most famous ones. Of course, more often the bigger nation prevailed, but the conflict was nowhere near one-sided and determined from the start as is usually the case in Civ games.
In other words, it should be relatively easy for a large nation to defeat a smaller one in one or more battles, but it should be increasingly difficult to completely destroy and annex it. Also, there should be a chance of revival once you have been overrun. The first historic examples that come to mind are Balkan states before and after Turkish invasion, Poland, Israel, to mention only European examples where statehoods and national traditions are more clear-cut. 
Another reason for setting this as a goal is the fact that in more standard rulesets, an empire of 2X cities is more powerful than two allied players with X cities each. A logical consequence of this would be that, if alliance wants to win, it is best to concentrate most power and land with one player and tempts others to make concessions toward him to more easily achieve team victory. But, however reasonable and desired this beehaviour should be in social circumstances, this isn't really what a game of Civilization is about.
3. More balanced amount of commitment in early and late game
In line withe the previous goal of allowing the more casual players to enjoy the game, another aim is to prevent the game being too slow and boring in the beginning and completely hectic and out of control at its end. In single-player this is not such a problem because you press "End Turn" when you feel like it, but in a fixed-length multiplayer this can be an issue. Basic and classic rulesets don't really care about this and growth ends up being exponential. At best, Longturn rulesets managed to decrease this to linear progression, but the goal of Simulation ruleset is to turn it into logarithmic: rapid expansion at start and then, as the number of units and cities grow and the time needed to manage maintenance increases, things don't go out of hand. Of course, people who love micromanaging and have a lot of time to throw into it will always have the advantage, but then Goal #2 kicks in.
4. Less rigid gameplay
In other rulesets initial city placement and initial expansion may amount to 90% of victory. If you screw this up, you have no chance to recover for the rest of the game. Simulation ruleset allows much more flexibility and requires that you make good decisions throughout the game. Naturally, a a good start is always a bonus, but apart from bad decisions (than may have even looked good at the time), the start may be influenced by bad starting location, unfavourable neighbours or other circumstances you had no control of. In other rulesets, this will have a major effect on the rest of the game. The goal of the Sim ruleset is to force you to make good decisions the whole time.
...
The main mechanics of achieving these goals are:
* tech upkeep per city (the more cities you have, the more upkeep you pay)
* active and rebellious citizens of conquered cities (nationalities)
* extra defence in the capital
* Tribal government and it bonuses for rapid expansion 
Also, as the ruleset is more and more developed, the plan is to introduce less empire-wide and more city-wide Wonder effects and perhaps unhomed population units that can escape and rebuild elsewhere.
Of course, every goal can be met or missed. But the development of Simulation ruleset is an ongoing project and, as always, comments, opinions and ideas are more than welcome.
==Basic strategy==
Simulation ruleset is probably most different from the "standard" ruleset(s) that you have ever encountered. Probably. So in order to prevent players from making some starting mistakes, let's lay out some basic tips. Of course, with the ruleset being very new compared to all others that are widely played, it should be noted that the strategies are still being developed and that the things listed here are only advisory. If you get an idea different from what is written here or would like to try something out, do so by all means. 
For starters, in early game this is a "smallpox" ruleset. This means that it is definitely worth it to spawn as many cities as possible very close to each other. More cities early means more worked tiles, more Food, Production and Trade, and close together means less corruption (due to smaller distance from the Palace) once it becomes relevant. In this ruleset (unlike in others), Tribal government has a slight food bonus. (Tip: due to several effects influencing each other, this bonus works best if the town is built on a tile that by default gives not 1 food. This means that 2 or 3, or even 0 (zero) are fine.) However, this bonus stops when you exit Tribal government and after that it's business as usual.
At some point you will realise that Tribal government has run its course. When that will happen may depend on many things and when to perform your first government change will be the decision to make. After that the game changes because, as you start acquiring technologies, you also start paying for tech upkeep and, along with the number of bulbs researched, it will also depend on the number of cities. So as the game progresses, you may want to drop the "smallpox" approach. But, again, when exactly this should happen is the question that can make or break your game.
The general recommendation for the post-Tribal period is to designate some cities as urban centres and allow other settlements to migrate into them. Of course, it will not be worth it to build all (or any) infrastructure in small cities that may be dismantled so you may want to start planning early. Check the appropriate section in this manual for details about migration. There is also a migration calculator in the works to help you out, but it's not complete yet.
As the game progresses, even in post-Tribal period it may be feasible to continue spawning towns and dedicate them immediately to producing science (by employing scientists) and let them oscillate in size between 1 and 2 in order to pump large cities with population. A breaking point may be the moment you realise that a single city costs more tech upkeep than it's worth the science it produces, but this is a soft limit and, again, approaches may differ on this very much.
Another advantage of Tribal government that it can also spawn units endlessly with no regard for logistics (for now), while later governments have to pay hefty upkeep. Hopefully, this may produce many conflicts between huge backward empires and smaller, more advanced nations. Hordes of low level Raiders vs. a selection of Chariots, Knights and maybe even Musketeers. What's there not to like?
As always, comments, ideas and stories of battles you went through are most welcome and if you check a new strategy and it works, we want to hear all about it.
==Short summary==
This ruleset is drastically different from other rulesets that are currently in play and shared around the community. There is a wide collection of changes ranging from city growth and management, government features, to war and unit upkeep. Here is a short list of the most important changes:
*IMPORTANT! There is a stack limit! More than 2-3 units on the same tile means defence penalties. More than 8 to 10 units on the same tile will usually mean Defence=0. Check below for details!
*Unit healing is slower, even with Barracks and similar facilities
* Tribal government is the default: low or no tech, no Trade, cheap Settlers (Tribe)
* cities start with minimal working areas (4 tiles only) and grow with size and improvements
* units are cheaper to build, but much more expensive to upkeep
* unit upkeep is mostly independent of government: the main exception is units in Democracy eating 2x food than in other governments and units under Tribal government not using city's food at all
* game starts with all nations under Tribal government; a Palace needs to be built in order to progress to Despotism
* there is a class of units (archers, catapults, cannons etc.) with “Bombarder” property: when they attack, they damage the defenders, can’t kill, but in return, do not receive damage when attacking
* granary levels are changed: now small cities grow faster and large cities grow slower
* spontaneous migration is enabled; population will occasionally move from from smaller and less developed cities into larger and more developed ones if they are close by; this can be controlled with use of some buildings
* no civil war; unhappiness does not depend on empire size
* corruption depends on distance from the capital; waste depends on tech level only
* veteran levels are reshuffled: there are more of them and they increase unit strength mostly by 10%; Also, they are acquired by more improvements, but also some governments
Of course, in order to get a better insight into the changes, check this whole manual.
More important changes regarding buildings and unit stats are covered in this manual, but there is a number of  "small changes" that are not because it would make this page cumbersone and less transparent. In-game help should be used extensively. Specifics that should be paid attention to: damage does not slow down units, Triremes are Monarchy only, Marines are weaker than in more traditional rulesets, Alpine Troops are now called Commandos and serve as City Busters, Shipyards are required to build modern warships, naval units cause no unhappiness when on a mission, naval units can not be upgraded, some upgrade chains are cut or reshuffled (Armour!).
= City management and demographics =
== Growth and expansion ==
The most important change about cities is that they have no constant working radius like most “standard” rulesets. Instead, they start at the smallest possible radius which only allows them to work the adjacent four tiles (as marked by red lines when a settler is selected). The radius squared (or r2) grows:
* by 1 when city size grows by 1
* by 1 when Granary, Courthouse, Barracks (all), Walls, Aqueduct, Harbour are built
* by 2 when Mass Transit, Police Station, Supermarket and Sewer System are built
Maximum size that can be reached by adding Migrant units is now 16 (used to be 8 in more standard rulesets).
HOWEVER, Migrant unit is now “unique” which means only one can be in play at the same time. Also, while there is one Migrant unit active, another one can’t be built nor it can be started to be built. Furthermore, by its mere existence, a Migrant unit causes considerable unhappiness in the city where it is built.
Minimum distance between cities is 1 (one), which means cities can be placed next to each other.
Building Settlers reduces city population only by 1, not by 2 as in LT rulesets.
Important! Aqueduct and Sewers are no longer the hard limit for city size. However, plague chance is more significant than in standard rulesets so you will have to build both (and Hospitals) in order to make it possible for cities to grow.
illness_base_factor = 75
illness_min_size = 4
Graphical calculation of chance of plague is available here: https://www.desmos.com/calculator/az8toikgfj 
(red: no improvements; blue: aqueduct; green: aq. & sewers)
Medicine doesn't improve health; instead, there is a new building: Hospital.
== Migration ==
Spontanious migration is enabled. This means that population will migrate from smaller and less developed cities to big ones. There is only partial control over this proces: Granary will decrease the chance of population migrating from the city, while a new improvement, City Hall, will increase the chance of population migrating into the city. Also, size 1 city is less likely - but not impossible - to lose its population and disband due to migration.
Approximate tips (buildings, location and other factors may nullify this):
* city size 1 is relatively safe from disbanding by migrating to size 6 or less;
* with Granary, city size 1 is relatively safe from migrating to city size 15 or less with City Hall
For technical details, consult Math of Freeciv with the following data:
Migration_Pct adjustments:
* city size 1: +100
* City Hall: +200
* size 1 and Granary: +1000
== Food and granary ==
Foodbox sizes are also heavily reorganised in order to bridge the gap between growing to size 2 and growing to sizes 3 and more. The additional feature of this particular distribution is that small cities grow faster than big cities. The table listing food left after growth (with Granary) and food needed to grow is shown below. Obviously, without Granary improvement, food left after growth in cities with size 5 and more is 0 (zero).
Also Supermarket is no longer the prerequisite for utilizing farmland. It is possible to build farmland with discovery of Engineering. The purpose of Supermarket is now "second Granary", operational at sizes 16 and above, again, set up in such a way for the food surplus transition to go smoothly. The Supermarket food table is also below.
GRANARY
City size	Food after growth	Max food
1 	 	
10 	 	
2 	2F 	12
3 	4F 	15
4 	6F 	18
5 	8 	22
6 	10 	26
7 	12 	30
8 	15 	35
9 	20 	40
10 	25 	50
F - free Granary
SUPERMARKET & GRANARY
City size	Food after growth	Max food
15 	50 	100
16 	60 	110
17 	70 	120
18 	80 	130
19 	90 	140
20 	100 	150
21 	110 	160
22 	120 	170
23 	130 	180
24 	140 	190
25 	150 	200
== Infrastructure ==
New building: Manufaktur (with Monarchy) gives +2 Shield to the central city tile. Once you discover Industrialization, Manufaktur turns into a museum and gives 2 Trade instead.
NO TERRAIN TRANSFORM (except: ocean <-> swamps)! Instead:
* Building a Railroad on hills and mountains gives them +1 Trade
* Researching Explosives makes it possible to build Resorts on Hills and Mountains, resulting in +2 Trade
* Offshore Platform removed
* added Port Terminal: +1 Trade on Deep Ocean tiles
* Farmland can be built in deserts.
*Taxmen/Scientists can not be employed before building Marketplace/Library and give only 1 gold/bulb. This increases by 1 with Bank/University and Stock Market / Research Lab. (Like in standard rulesets, some wonders may also affect this.)
= Governments, diplomacy, waste and corruption =
Most governments have been left intact. However, Tribal government has received a complete rehaul. Also, while Communism has been a bit more differentiated:
* Five Year Plan wonders have been introduced for increased production
* under Communism, Bank doesn’t give 50% more Luxury and Stock Market doesn’t work at all
* celebrating communist cities have increased Shield production instead of Trade
Governments also influence veterancy level of combat units. Units built in Democracy receive no veteran bonus, units built under Republic or Fundamentalism receive 1 veteran bonus level, Tribal units receive 3 (three) while all others governments give 2 veteran bonus levels.
All governments except Despotism, Tribal and Anarchy receive +10 Trade in the capital.
When in Anarchy, unhappysize is 1 causing cities to be in revolt by default. Also, specialists have no effect in Anarchy.
== Tribal government ==
Tribal government is now more special. All nations start with Tribal government and need to build the Palace in order to progress to Despotism. Tribal government has the following features:
* no Trade
* no specialists
* military units effectively operate without needing food from city granary ("Food Upkeep Free" : 99)
* military units produced in Tribalism have 3 Veteran levels; however, Barracks don't have further effect
* settlement is performed by "Tribe" unit (obsoleted by Settler as soon as you form a non-Tribal government)
* every city produces +1 food on its central tile
* once the Palace is built, the capital produces additional +1 food
* early governments tile penalty is unconditional: cannot be cancelled by researching Tools or building Pyramids
* up to 2 units can provide martial law and they make content 1 population each
* by default, cities start becoming unhappy after the 2nd citizen
* a nation can not revert to Tribal government once Alphabet or Currency have been discovered
New units, unique to Tribal government, are replacing other units that can't be built under Tribal government:
* Tribe (replacing Settlers), at lower price - if Tribe is outside of a city for more than 2 turns and/or doesn't build a new city, it dies
* Raiders (replacing Phalanx), can attack from boats
* Bowmen (replacing Archers)
* Boat (replacing Trireme) - slower, can carry only 1 unit
== Trade ==
Maximum Sci/Tax/Lux rate is reversed: under Despotism you will have full control over your nation and can designate Trade up to 100% for any department. In Monarchy & Communism maximum is 80%, in Fundamentalism it is 70%, Republic has 60% and in Democracy, as a sovereign, you have least control and can only adjust it to maximum of 50%.
Trade routes are possible only between capitač cities if you are not at war with their nation.
Waste doesn’t depend on government. Instead, it depends exclusively on technology level. Base waste is 50%. Following techs reduce waste by 5% : Alphabet, Writing, Trade, Physics, Invention, Chemistry, Electricity, Refining, Mass Production, Robotics.
Corruption depends on distance from the capital, except under Communism and Democracy where it is constant throughout the nation. It can be reduced by a number of buildings in the city. However, the effect of a particular building depends on the government. Table below shows corruption reduction by particular buildings for a particular government.
* % per tile - for each tile away from the capital, corruption increases for this percentage
* 100% at - without any buildings, corruption is 100% at this distance from the capital
 	Base %	% per tile	100% at	Temple	Courthouse	Cathedral	Police	Library/University
Despotism	25 	5 	15 	25 	30 	25 	10 	-
Monarchy 	25 	4 	19 	15 	40 	20 	20 	-
Funda 	25 	4 	19 	30 	10 	30 	20 	-
Republic 	30 	2 	35 	5 	30 	20 	20 	5/10
Democracy	40 	- 	N/A 	5 	30 	20 	20 	5/10
Communism	50 	- 	N/A 	- 	25 	10 	30 	10
== Diplomacy ==
You don’t need an embassy to make treaties! All your units can serve as temporary emissaries: you can make treaties while - and one turn afterwards - any of your units is in contact with the other nation’s unit. You can still make an embassy for more permanent contact and espionage.
Atlantic Telegraph Company from the LT rulesets, allowing embassies with everybody, is replaced by Marco Polo (Banking). Furthermore, embassies with everybody are automatically created after you discover electricity.
= The art of war =
One of the biggest changes in the game concerns units. For starters, assume "everything has changed" and, before researching or building a unit, check in-game help. Also, consult this because some change information may be not suitable for in-game help.
A MUST-CHECK complementary resource is the Sim ruleset units table.
== Stack limit ==
A new and very important change is a soft STACK LIMIT! This means that, after a certain limit, more military units on the same tile receive a defence penalty. Namely: for every unit above the Limit, all units receive -25% defence penalty. This means that with too many units on the same tile, their defence value may reach zero!
Default Limit is set to 3, except if they are on a Mountain tile, in which case the limit is 2.
Additionally, if units are in a city, Limit is increased by 1 for each 5 city sizes (new Max at 1, 5, 10, 15 and 20).
For your convenience, the limits are placed in a table.
NOTE: Depending on a ruleset and/or a particular game, it may not be possible to build a city on a mountain.
Also, because this is a new and revolutionary feature, it may go through some tweaks so always check this space.
Maximum number of units on a tile for no penalty:
Tile 	no-mountain	mountain
No City 	3 	2
City 1-4 	4 	3
City 5-9 	5 	4
City 10-14	6 	5
City 15+ 	7 	6
== Upkeep ==
The principle of upkeep has been changed very much and upkeep cost increased. Now units are cheaper to build, but need much more gold, shields and food to be kept operational. Gold cost increases from early ages to the later, and in Democracy financial cost is doubled. Also, more technically demanding units (catapults, ships, armour) also require production upkeep.
Units now need much more food. By default, each unit requires 1 food (except elephants who, naturally, need 2). However, there are two major discounts. Firstly, table below shows “free upkeep per city”.
 	Gold	Shield	Food	Unhappy
Anarchy 	99 	99 	99 	99
Tribal 	99 	99 	10 	99
Despotism 	2 	2 	5 	99
Monarchy 	1 	1 	4 	99
Republic 	0 	0 	2 	2
Fundamentalism	2 	1 	5 	99
Communism 	1 	2 	2 	99
Democracy 	0 	0 	2 	0
Additionally, each 2 city sizes supply free food to one unit. For example, under Despotism, a city size 4 provides 7 units of food to its units at no cost (meaning 7 non-elephant units food-free) because 5 + 4/2 = 7. Note: the core unit of measurement here is “free food”.
== Bombarders ==
Archers, catapults, cannons, artillery and howitzer now have Bombarder property, as well as submarines, helicopters and aerial bombers. This means that, when they attack, they are only able to damage a unit, not destroy it. However, because attacking from distance, they also don’t receive any damage during this attack. (Naturally, if they are under attack from a unit, combat happens normally and they can be destroyed.) Also, when bombarding a stack of units, all units in a stack receive damage. Note: effective strength of Bombarding units is decreased compared to standard rulesets so you will need more of them to seriously damage a well fortified defender.
There have been complaints that this uncovers the number of defenders in a city, but one man’s bug is another man’s feature.
Air units: Bombers AND Fighters are now"Bombarders". The reason for this is that a unit does not represent a single airplane, but an airfleet, and those don't get destroyed, only damaged and reduced. Damaging an airfleet in Civ has the same effect as in reality: it makes it less combat worthy and increases time until it is ready again. Also, make sure the upkeep cost is large enough so that there is no overproduction.
== Veteran levels ==
Veteran levels are no longer 150%, 175% and +25% onwards, like they were in more standard rulesets. Now they are as follows:
100, 110, 120, 140, 150, 160, 170, 180, 200, 220, 250, 275, 300, 325, 350
Also, more buildings make freshly produced units veteran. Barracks will raise veteran level of a unit by 3 (three), while all University, Cathedral and Bank will additionally raise veteran level by 1 (one), due to better skills, equipment and morale. Furthermore, as was already mentioned, all governments except Democracy also raise this: Republic by 1 and all others by 2. Because in more advanced societies general population, deprived of the need for rebelion, tends to get lazy.
== Movement ==
Movement cost on some types of terrain is also changed, so be sure to check in-game help.
== Military unhappiness ==
Women’s Suffrage has been removed! If you want your people to accept foreign interventionism and stay at home instead of protesting in the streets, either bring home the goods in the form of luxuries or invest in stupid TV shows to keep them dumb and chained to their screens.
Relevant for this section: fortress doesn’t change tile ownership.
Under Democracy, a University in the city increases unhappiness by 1 per aggressively deployed unit.
== Other conflict-related stuff ==
* Due to national pride, elite guards, citizens loyalty etc., capital (with Palace) gives 200% defence bonus
* city defence bonus rises by 10% per size point until size 10 (max 100%).
* Paratroopers and Commandos: added "CityBuster" flag - doubled strength when attacking cities.
* Helicopters can carry one unit: Land (infantry), Spies, Diplomats and Explorers
* on top of the usual, Submarines and Carriers can carry Diplomats, Spies and Missiles
* incite city base costs increased x10.
* One veteran level lost when upgrading a unit.
* Civil war disabled.
* NATIONALITY: ON; when you conquer a city, 51% of its population will be unhappy if belonging to the enemy nationality
* when your palace is conquered, you don't get another one automatically, you need to rebuild it yourself
* no upgrades across classes (cavalry can't be upgraded to armour)
* no automatic upgrade at all (no Leonardo)
* invention does NOT halve the upgrade price
* Freight can carry 2 missiles (including Nuclear)
* Scorched earth: most or all buildings are destroyed upon city conquest
* Bombers losing 20% HP per turn when outside
* No units with "Killcitizen" flag except Raiders (Tribal government): population is not decreased when city is attacked
* Caravans and Freights no longer capturable
* Ships do not become obsolete and can't be upgraded. Exception: Cruiser -> AEGIS Crusier
* Trireme is Monarchy-only (Boat, however, is universal)
* damage does not slow units down (possible variation: this may apply only to fast or all attack units, depending on the particular game; check the in-game help)
* there are more building slots available, meaning it may be possible to build mroe units of the same type in one turn; City hall and sizes 10, 20 and 30 each increase this by 1 (for a maximum of 5)
* All units have additional defense against fast units (except against Mech. Inf.) on some terrains:
** forest, hills: +50%
** swamp: +100%
** mountains: +200%
= Technology =
Note: fine-tuning is still in process so the numbers here may not be accurate for every game. Before making decisions, inquire about the exact figures or check for them in the ruleset.
Tech upkeep is ON. This means that every turn you pay upkeep in bulbs, depending on how many technologies you have in your knowledge base. The more cities you have, the more upkeep you pay. This has almost no effect in the first part of the tech tree but, for reference, the whole tech tree cost is around 120,000 bulbs which makes Tech Upkeep at the end of the game 120 bulbs per city.
Technical details:
Equation: 
upkeep = ((bulbs / divider) - free) * cities
Tech_upkeep_divider set to 2000
Tech_upkeep_free set to 0 (base), 1 (Tribal only) and 10 (Anarchy only).
Among other things, this means no tech upkeep for Tribal government until you research 2000 bulbs worth of technologies.
There is still tech upkeep in Anarchy, although smaller, so choose the moment wisely and prepare for a potential tech loss.
Bridge Building tech doesn't exist anymore. Its role (build roads across rivers) has been taken by Construction.
New tech: Tools (preq: Pottery, Bronze), removes the 3+ penalty (like Pyramids and non-Despotism)
There are between 10 and 20 more tech-tree reshuffles and a few more added techs so examine it more closely as you play the game!
Exchanging and stealing techs
It is not possible to exchange technologies the conventional way, through diplomatic treaties, but you can use Diplomats and Spies to “steal” them - willingly from your allies or unwillingly from your enemies. Base chance to steal will depend on an individual game, the standard value should be 50%, but make sure before doing actions. Also, previous games showed some discrepancy so we are yet to be absolutely sure how this mechanics actually works. What we are fairly certain is that a Diplomat can NOT steal technology from the same city twice, while Spy may (taking into account other penalties).
Multiple Diplomat units exist, but the only difference is their production cost because “it takes more resources to train them to acquire more complex technologies”.
Barracks, Courthouse, Police Station each add 25% to Spy Resistance (bonus defence for a defending Diplomat/Spy). No defender - no bonus.
= Game-to-game variations =
Not all Sim games will have identical rules. Changes should be down to a minimum, but some will happen, mostly for testing reasons and eventually some of the variable features may become permanent. For now the following things may differ from game to game and they should be checked for each individual game:
* empire sizes (unhappiness by size); by default, there is no unhappiness by size, but this feature may be tested
* DamageSlows: by default, this will be OFF (meaning full MP for damaged units); depending on a particuar game, it may apply only to fast or all attack units; check in-game help!
= Technicalities, tables, appendices, quick reference, stuff&stuff... =
Units table:
https://docs.google.com/spreadsheets/d/1Caw6CCHnfrHP6oWOPK8cFbFxkWCuZllaEiFso_kT55Q/edit?usp=sharing
The files for the ruleset are located here:
https://github.com/longturn/games/tree/master/SIM25
Tileset changes listed and files offered here:
http://forum.freeciv.org/f/viewtopic.php?f=12&t=91155&sid=9824922e9ae27824cb7cb5471683282e
= Changes from previous versions =
Here is a VERY rough and raw list of fixes and changes made between previous versions of the ruleset.
** New in v2.99 (Freeciv 2.6, played in LT56) ==
For now, check forum thread at http://forum.freeciv.org/f/viewtopic.php?f=11&t=90758&p=99962#p99962.
== New in v2.2 ==
VARIATIONs, MAY BE IMPLEMENTED IN PARTICULAR GAMES:
* Tribal: size 20, step 2; Despotism: size 50, step 2 -
* DamageSlows: by default, this will be OFF (full MP for damaged units); depending on a particuar game, it may apply only to fast or all attack units; check in-game help!
Fixes:
- taxmen (???)
- some units - mounted mostly - from "Big Land" to "Land"; now only "long range" remain "Big Land"
- Skirmishers should be Bombarders!
Granary cost 30 -> 20
City hall 50 -> 40
Manufaktur 40 -> 30
- City_Build_Slots
[b]WARNING![/b] IgTer units now use full move point per tile, not 1/3. 
fixed rails (1/9 MP instead 1/6)
Pre-fort noStackDeath removed
Alpines -> Commando 20 ->30
Caravan cost 50->30; upkeep = 3 gold!!!
Ironclad is Trireme (check tech), move 6, cost 30
Naval units - no unhappiness
Set air units "Unbribable"
Adjusted veteran raise chances, now slightly less chance.
Navigation -> Advanced Navigation 
Magnetism -> Navigation
Navigation = Astronomy + Seafaring 
Advanced Navigatio = Navigation + Invention 
Physics = Philosophy + Astronomy 
Industrialization = Banking + Engineering (was Railroad) 
Remove Guerrilla Warfare 
Flight = Machine Tools + Mass Production 
Environmentalism = Labour Union + Recycling 
Automobile = Combustion + Mass Production 
Mass Production = Corporation + Machine Tools
Destroyer: Steel
Cruiser: Combustion
Partisans to Communism
Fanatics to Communism
Marines should be weaker ("Early marines")
Paratroopers to Advanced Flight
Mech. Inf. to Combined Arms
Tech_upkeep_divider set to 2500
Tech_upkeep_free set to 0 (base) and 1 (Tribal only)
Among other things, this means no tech upkeep under Tribal government until you research 2500 bulbs
veteran progression chance slowed down for both workers and military
Migration range: 2 -> 1
Navigation -> Advanced Navigation
Magnetism -> Navigation
Steel: Shipyard I: Destroyer
Combustion: Shipyard II: Cruiser, Submarine
Mass Production: Shipyard III: Battleship
Port Terminal possible to build like Harbour
Steam Engine = Chemistry + Metallurgy
Naval Doctrine = Advanced Navigation
Engineering: Farmland
Steel: Shipyard I: Destroyer
Combustion: Shipyard II: Cruiser, Submarine
Mass Production: Shipyard III: Battleship
"DamageSlows" removed altogether!
No farmland on city tile
Supermarkets: 2nd step Granaries
[code] 
 15 50 100
 16 60 110 5%
 17 70 120 8%
 18 80 130 12%
 19 90 140 14%
 20 100 150 17%
 21 110 160 19%
 22 120 170 21%
 23 130 180 22%
 24 140 190 24%
 25 150 200 25%
[/code]
City Hall: +2 content
*** Governor's Office: cost 20, upkeep 3, decreases corruption 80%, only in Monarchy
*** Tax Office: cost 20, upkeep 5, decreases corruption 90%, only Republic/Democracy
*** Commissar's Office: cost 20, upkeep 5, decreases corruption 90%, only Communism
all three influence migration
Copernicus Observatory: 300 -> 100
----
veterancy! - marketplace, library and temple removed; of civilian buildings, only university, cathedral and bank give veterancy
Ships do not become obsolete and can't be upgraded. Exception: Cruiser - AEGIS Crusier
Trireme is Monarchy-only
Caravan upkeep
removed DamageSlows
Cities with a City Hall and more size can build more identical units at the same time (if shields are provided): +1 for Hall, sizes 10, 20, 30
Tribe unit moves 3 tiles, regardless of terrain
== New in v2.1 ==
Tribal government -----
"Tribe" unit - Same as Settler, but:
* 10 HP
* cost 10
Also in Tribal:
* +1 food in every city
* +1 in capital (Palace) (+2 total)
* Tile penalty - unconditional
* type = "Martial_Law_Max"
* value = 2
* type = "Martial_Law_Each"
* value = 1
Other:
* specialists have no effect in Anarchy
* Bombers losing 20% HP per turn when outside
* removed Shakespeare's Theatre
* No units with "Killcitizen" flag: population is not decreased when city is attacked
* Caravans and Freights no longer capturable
* Max_Trade_Routes = 0
----
== New in v2.0 ==
When in Anarchy, unhappysize is 1 making cities to be in revolt by default.
- city defence bonus rises by 10% per size point until size 10 (max 100%).
Tribalism: no money (tax or any upkeep cost), no taxmen, scientist gives only half (one bulb), +3 veteran levels
New tech: Tools (preq: Pottery, Bronze), removes the 3+ penalty (instead of Pyramids and non-Despotism)
Fixed Manufaktur: now stops working with Factory built and serves as a museum.
All production bonuses (Factory, Mfg, Plants...) are 50%
Prerequisite switch:
Republic needs Philosophy (was Literacy)
Democracy needs Economics (was Banking)
Tech_upkeep_divider set to 2000
Tech_upkeep_free set to 1 (base) and 2 (Tribal only)
Among other things, this means no tech upkeep until you research 2000 bulbs (or 4000 for tribal government).
Migration_Pct adjustments: size 1, +100; City Hall, +200; size 1 & Granary, +1000 (10^3)
Approximate tips:
- city size 1 is safe from disbanding by migrating to size 6 or less;
- with Granary, s1 is safe from migrating to s15 with City Hall
Equation:
upkeep = ((bulbs / divider) - free) * cities
Anarchy: No Trade!
Monarchy: +10 Trade in capital (Palace)
New units, unique to Tribal government, also replacing other units that can't be built under Tribal government:
- Raiders (replacing Legion and Pikemen), can attack from boats
- Bowmen (replacing Archers)
- Boat (replacing Trireme) - slower, can carry only 1 unit
Bombers AND fighters are "Bombarders". Explanation: a unit doesn't represent a single airplane, but an airfleet, and those don't get destroyed, only damaged and reduced. Damaging an airfleet in Civ has the same effect as in reality: it makes it less combat worthy and increases time until it is ready again. Also, make sure the upkeep cost is large enough so that there is no overproduction.
Scorched earth: most or all buildings are destroyed upon conquest.
Tribal government can't build Triremes, only Boats.
New units: Skirmishers, Arquebusiers, Boats
Arquebusier (2/2 - 20/1) - Gunpowder
Musketeers (3/3 - 20/1)
No more "killcitizen"
Gunpowder = Feudalism + Physics
Leadership = Theology (not Chivalry) + Banking
Removed Leonardo
set diplchance_steal=50
set techlost_recv=0
/set unreachableprotects disabled
Catapult (et al.) should attack non-native tiles.
no upgrades across classes
Add pre-fort (and check fortress border) (terrain.ruleset) - remove "NoAggressive"
All governments except Despotism, Tribal and Anarchy: +10 Trade in the capital
Barracks don't work in Anarchy and Tribal
Farmland can be built in deserts.
Freights can carry 2 Missiles
City foodboxes now corresponding to Manual (now granary_food_ini = 10, 12, 15, 18, 22, 26, 30, 35, 40)
(?) Diplomats couldn't travel by roads and rivers?
Tribal government gets no Trade
Tribal scientists produce 1 bulb (instead of 2)
Tribalism, food upkeep free : 99
Fixed Manufaktur:
+2 shields
with Factory, 2 Trade instead of 2 Shields, no effect on Factory construction
Freight can carry 2 missiles
No automatic upgrade at all
Invention does NOT halve the upgrade price
New/changed techs:
Physics = Philosophy + Feudalism
Alchemy = Trade + Philosophy
Chemistry = Alchemy + University
Gunpowder = Alchemy + Feudalism
Leadership = Gunpowder + Chivalry
Monarchy fix (+20 -> +10 trade)
Warriors obsolete by Raiders
Raiders obsolete by Militia
Celebrating communist cities have increased shield production.