How to update a ruleset from 2.5 to 2.6

This document describes how to convert freeciv 2.5 compatible ruleset to development version (one that will become freeciv 2.6) compatible ones. Currently this goes up to compatibility with freeciv S2_6 revision 29663.

Capability

Capability string of each ruleset file must be changed:

[datafile]
options="+Freeciv-ruleset-Devel-2014.September.14c"

Versioning

Optional versioning of the ruleset is now supported. You can add the version string of the ruleset to game.ruleset [about] section. That version is displayed to the user in client Help -> About Ruleset, and stored to savegames. Note that this ruleset version has nothing to do with freeciv version, though many rulesets prefer to have freeciv major version that the ruleset is compatible with in the beginning.

Ruledit metadata

Ruleset editor freeciv-ruledit needs some metadata to function correctly with the ruleset, especially when saving it back again after editing.

Nations.ruleset

Metadata is in section [ruledit]. If nations.ruleset should not contain all the nations saved to it, but should include separate list of nations, such as default/nationlist.ruleset, that nationlist should be given in nationlist -entry.

[ruledit]
nationlist = "default/nationlist.ruleset"

Nations that are not part of such an nationlist, should be listed in embedded_nations. This is needed only if nationlist is defined, otherwise all nations are automatically embedded.

embedded_nations = "Animal Kingdom"

Extras

All of old hardcoded specials, bases and roads are extras. You must add section for each extra to terrain.ruleset. Bases and Roads still have separate sections for their additional properties. These base and road sections are linked to specific extra section by field extra.

[extra_farmland]
name = _("Farmland")
category = "Infra"
causes = "Irrigation"
rmcauses = "Pillage"
graphic = "tx.farmland"
graphic_alt = "-"
activity_gfx = "unit.farmland"
act_gfx_alt = "unit.irrigate"
rmact_gfx = "None"
rmact_gfx_alt = "-"
reqs =
  { "type", "name", "range"
    "Tech", "Refrigeration", "Player"
    "Extra", "Irrigation", "Local"
  }
build_time = 0
removal_time = 0
conflicts = "Mine", "Oil Well"

Requirements

Requirements are defined for all extras in their extra section. This replaces old requirement vectors in base and road sections for them. For old specials, proper requirements must be added. See classic ruleset for requirements matching old hardcoded behavior. For bases and roads you should just move the requirement vectors from base and road sections to extra section.

Categories

These categories match old hardcoded rules of specials: Irrigation, Mine, Farmland: Infra Pollution, Fallout: Nuisance Hut: Bonus

All of bases and roads used to be handled as Infra but now that it's possible to define them one by one, you may want to adjust that (Rivers would normally be Natural rather than Infra, and some special bases Bonus)

Buildable property

Whether extra is buildable is defined for all extras in their extra section. This replaces old buildable fields in base and road sections for them. For old specials you may want to set this to FALSE if the extra should not appear in the game at all (leaving requirements vector empty would mean extra is buildable always). For bases and roads you should just move the buildable field from base or road section to extra section.

Pillageable property

Extra is defined to be pillageable by adding Pillage to rmcauses (removal causes) list. This replaces old pillageable fields in base and road sections. You should just add rmcause Pillage in extra section of all the bases and roads that have had pillageable property TRUE, and not for others. To keep old hardcoded behavior, only Pollution and Fallout of the old specials should get rmcause Pillage.

Names

Huts were called "Minor Tribe Village" in the clients and "Hut" in save games. To keep that add it like this:

[extra_hut]
name           = _("Minor Tribe Village")
rule_name      = "Hut"

Conflicts

There can be conflicts between any two extras defined in their extra sections. This replaces old conflict definitions between base types only. For old specials, some conflicts should be defined to get old hardcoded behavior; Mine should conflict with both Irrigation and Farmland. To keep old conflicts between bases, just move conflicts field from base section to their extra section.

Native to

All extras have list of unit classes it's native to in their extra section. This replaces old native_to fields in base and road sections for them. For old specials there's no need to define them native to any unit to get old behavior. For bases and roads you should just move the native_to field from base or road section to extra section.

NativeTile flag

NativeTile extra flag has replaced base and road flags with the same name. Just remove the flag from base and road sections, and define it in extra sections of those bases and roads that used to have it.

ShowFlag flag

ShowFlag extra flag has replaced base flag with the same name. Just remove the flag from the base sections, and define it in extra sections of those bases that used to have it.

Refueling

Fuel using units no longer refuel on all native bases. Instead any extra that could act as refueling point for native units, must have Refuel flag. To keep old behavior, add flag to extra section of all bases.

Defense bonus

All extras have defense_bonus. This replaces old defense_bonus fields in base and road sections. Just move defense_bonuses of bases and roads to extra sections to get the old behavior.

Hidden by another extra

Any extra can hide any other extra with hidden_by property. This replaces similar feature that was limited to hiding roads with other roads. To just keep the old functionality, move hidden_by from the road section to the extra section of the same road extra.

AlwaysOnCityCenter and AutoOnCityCenter

Base and Road flags AlwaysOnCityCenter and AutoOnCityCenter have been replaced with extra flags with the same names. Simply move flags from base or road section to the extra section of the extra.

Graphics tags

All the extras have graphic and graphic_alt tags in their extra section. Move old tag definitions from base and road sections to their extra section, and add tags for the other extras.

Activity gfx tags

All the extras have activity_gfx and act_gfx_alt tags in their extra section. Move old tag definitions from base and road sections to their extra section, and add tags for the other extras. These tags are used for activities that add the extra. For activities that remove the extra see rmact_gfx tag. Special value None is supported for cases where no activity creates the extra, such as rivers and huts added by map generation only, pollution resulting from city pollution only.

Extra removal activity gfx tags

Extras have separate rmact_gfx and rmact_gfx_alt tags for activities that remove the extra. These are used for cleaning pollution or fallout. Special value None is supported here too for extras that have no special removal activity.

ConnectLand flag

Any extra can have ConnectLand flag that used to be specific to roads. For any road having such a flag, remove it from road section, and add to extra section.

Natural Road Flag

Road flag Natural has been removed as obsolete. The only use that it had in 2.5 was to provide sdl-client with information what defense bonuses are to be considered natural for the tile. Now it's determined from the extra's category.

NoBonus Road move mode

Road move mode NoBonus has been removed. Instead you should set move_cost to -1 for such roads instead. This allows you to set combination of -1 move_cost and the move mode you really want.

Extra build_time

Extras have build_time property, replacing that of roads and bases. Move old build_time definitions from road and base sections to extra section. For other extras you may set build_time as 0 to keep old behavior of using terrain specific build times.

Pillage time

Extra removal time works similar way to the build time. This means that even for pillage activity, terrain specific execution time, pillage_time, has been added. Set it to 1 for all terrain types to mimic old behavior. Set removal_time for all extras to 0 to use terrain specific times as was the case in 2.5.

Environment upset

Only extras with flags GlobalWarming or NuclearWinter count toward environment upset. To keep old hardcoded behavior, add GlobalWarming to Pollution and NuclearWinter to Fallout

Extra requirement type

Requirement types Special, Base, and Road have been replaced with Extra requirement type. As you have extra type defined for all the specials, bases, and roads, this requires simply changing the requirement type text

reqs =
  {
    "Special", "Irrigation", "Local"
    "Base", "Fortress", "Local"
    "Road", "Railroad", "Local"
  }

->

reqs =
  {
    "Extra", "Irrigation", "Local"
    "Extra", "Fortress", "Local"
    "Extra", "Railroad", "Local"
  }

Farmland tech requirement

Tech flag Farmland has been removed as obsolete. Instead you should have such a tech as requiment for Farmland extra. If you had multiple techs with the flag, you need to create user tech flag, give it to all those techs, and to make that tech flag requirement for Farmland extra instead.

Bonuses from Extras

For getting tile output bonuses from extras, one has to define them as effects. Old versions used to have pollution and fallout penalties defined in terrain.ruleset. Those are now removed as obsolete. Here are effects matching hardcoded bonuses, and in case of pollution and fallout old defaults from terrain.ruleset, from earlier versions:

; Irrigation gives 100% of terrain irrigation bonus
[effect_irrigation]
type    = "Irrigation_Pct"
value   = 100
reqs    =
    { "type", "name", "range"
      "Extra", "Irrigation", "Local"
    }
nreqs   =
    { "type", "name", "range"
      "CityTile", "Center", "Local"
    }

[effect_irrigation_2]
name    = "Irrigation_Pct"
value   = 100
reqs    =
    { "type", "name", "range"
      "CityTile", "Center", "Local"
      "TerrainAlter", "CanIrrigate", "Local"
    }
nreqs   =
   { "type", "name", "range"
     "Extra", "Mine", "Local"
   }

; Mine gives 100% of terrain mine bonus
[effect_mine]
type    = "Mining_Pct"
value   = 100
reqs    =
    { "type", "name", "range"
      "Extra", "Mine", "Local"
    }

; Pollution or Fallout reduce output by 50%. Together 75% (and not 50% + 50% = 100%)
[effect_pollution]
name    = "Output_Tile_Punish_Pct"
value   = 50
reqs    =
    { "type", "name", "range"
      "Extra", "Pollution", "Local"
    }
nreqs   =
    { "type", "name", "range"
      "Extra", "Fallout", "Local"
    }

[effect_fallout]
name    = "Output_Tile_Punish_Pct"
value   = 50
reqs    =
    { "type", "name", "range"
      "Extra", "Fallout", "Local"
    }
nreqs   =
    { "type", "name", "range"
      "Extra", "Pollution", "Local"
    }

[effect_pollution_fallout]
name    = "Output_Tile_Punish_Pct"
value   = 75
reqs    =
    { "type", "name", "range"
      "Extra", "Pollution", "Local"
      "Extra", "Fallout", "Local"
    }

Extra helptext

Manually written helptext are now property of extras, not just bases and roads. Move helptext from bases and roads to equivalent extra section. For extras like hut there's no longer hardcoded help in help browser, but if you have any such extras, you should add the help there.

Mine appearance

Tilesets no longer have terrain specific sprite definition for mines, as there is no such hardcoded concept as mine any more, just generic extras. If you want to have distinct appearance for the mine on different terrains, you need to define distinct extras in the ruleset having suitable terrains as requirement (possibly via custom terrain flags to group them). Most of the supplied rulesets provide new extra named "Oil Well" to be used instead of "Mine" on terrains where most tilesets used to have oil derrick like mine graphics.

Nuke Contamination

Setting nuke_contamination from game.ruleset has been removed as redundant. You can control what kind of extras appear as an result to nukes by defining causes for the extras. If you define Fallout as cause for Pollution-extra, and maybe remove Fallout extra completely, then Pollution will appear as result of nuclear explosions. If you define Fallout as cause for Fallout-extra, then it will appear.

Terrains without pollution

NoPollution terrain flag is gone. If you need it, implement it as user terrain flag that is negated (not present) requirement for appearance of all pollution extras.

Extra ownership

Tile (borders) can now be owned by one player, and extras on it by another. This makes it possible to get rid of the common workaround of making bases territory claiming bases for their own tile at least, so that their owner will get their effects.

Requirement definitions

Negated replaced with present

Old negated property of the requirements has been replaced with opposite meaning present so that ruleset authour is not required to think in double-negations (negating negation).

reqs = 
  { "type", "name", "range", "negated"
    "Tech", "Masonry", "Player", FALSE
    "Tech", "Metallurgy", "World", TRUE
  }

->

reqs =
  { "type", "name", "range", "present"
    "Tech", "Masonry", "Player", TRUE
    "Tech", "Metallurgy", "World", FALSE
  }

Effect nreqs should be replaced with present=FALSE requirements

In none of the supplied rulesets effects use nreqs any more. Those are listed as present=FALSE requiremens in the normal requirements list instead. This is going to be the only supported way in the future versions.

reqs    =
    { "type", "name", "range"
      "Building", "Airport", "City"
      "UnitClass", "Air", "Local"
    }
nreqs   =
    { "type", "name", "range"
      "UnitFlag", "NonMil", "Local"
      "UnitFlag", "NoVeteran", "Local"
    }

->

reqs    =
    { "type", "name", "range", "present"
      "Building", "Airport", "City", TRUE
      "UnitClass", "Air", "Local", TRUE
      "UnitFlag", "NonMil", "Local", FALSE
      "UnitFlag", "NoVeteran", "Local", FALSE
    }

Action Enablers

Some previously hardcoded requirements for player actions have been made ruleset configurable with new action enablers concept in game.ruleset actions -section.

Sabotage City

To have city sabotaging be restricted the way it used to be with hardcoded rules, add action enablers like this:

[actionenabler_sabotage_city]
action = "Sabotage City"
actor_reqs    =
    { "type",   "name", "range", "present"
      "DiplRel", "War", "Local", TRUE
      "UnitFlag", "Spy", "Local", FALSE
      "UnitState", "OnLivableTile", "Local", TRUE
      "MinMoveFrags", "1", "Local", TRUE
    }

[actionenabler_sabotage_city_target]
action = "Targeted Sabotage City"
actor_reqs    =
    { "type",   "name", "range"
      "DiplRel", "War", "Local"
      "UnitFlag", "Spy", "Local"
      "UnitState", "OnLivableTile", "Local"
      "MinMoveFrags", "1", "Local"
    }

Poison City

To have city poisoning be restricted the way it used to be with hardcoded rules, add action enabler like this:

[actionenabler_poison_city]
action = "Poison City"
actor_reqs    =
    { "type",   "name", "range"
      "UnitFlag", "Spy", "Local"
      "DiplRel", "War", "Local"
      "UnitState", "OnLivableTile", "Local"
      "MinMoveFrags", "1", "Local"
    }
target_reqs    =
    { "type",   "name", "range"
      "MinSize", "2", "City"
    }

Bribe Unit

To have unit bribing be restricted the way it used to be with hardcoded rules, add action enabler like the following. This assumes you have user unit flag Unbribable defined. If you don't have units that needs such a flag, you can drop the line about Unbribable unit flag. If you don't make democracies immune to unit bribery remove the line about Democracy.

[actionenabler_bribe_unit]
action = "Bribe Unit"
actor_reqs    =
    { "type",   "name", "range", "present"
      "DiplRel", "Alliance", "Local", FALSE
      "DiplRel", "Team", "Local", FALSE
      "UnitState", "OnLivableTile", "Local", TRUE
      "MinMoveFrags", "1", "Local", TRUE
    }
target_reqs    =
    { "type",   "name", "range", "present"
      "UnitFlag", "Unbribable", "Local", FALSE
      "Gov", "Democracy", "Player", FALSE
      "CityTile", "Center", "Local", FALSE
    }

Sabotage Unit

To have unit sabotaging be restricted the way it used to be with hardcoded rules, add action enabler like this:

[actionenabler_sabotage_unit]
action = "Sabotage Unit"
actor_reqs    =
    { "type",   "name", "range"
      "Unitflag", "Spy", "Local"
      "DiplRel", "War", "Local"
      "UnitState", "OnLivableTile", "Local"
      "MinMoveFrags", "1", "Local"
    }
target_reqs    =
    { "type",   "name", "range", "present"
      "CityTile", "Center", "Local", FALSE
    }

Incite City

To have city inciting be restricted the way it used to be with hardcoded rules, add action enabler like the following. If you don't wish to make democracies immune to city incitement remove the line about Democracy. If you don't wish to make capitals immune to city incitement remove the line about Palace.

[actionenabler_incite_city]
action = "Incite City"
actor_reqs    =
    { "type",   "name", "range", "present"
      "DiplRel", "Alliance", "Local", FALSE
      "DiplRel", "Team", "Local", FALSE
      "UnitState", "OnLivableTile", "Local", TRUE
      "MinMoveFrags", "1", "Local", TRUE
    }
target_reqs  =
    { "type",   "name", "range", "present"
      "Gov", "Democracy", "Player", FALSE
      "Building", "Palace", "City", FALSE
    }

Establish Embassy

To have embassy establishing be restricted the way it used to be with hardcoded rules, add action enabler like this:

[actionenabler_establish_embassy]
action       = "Establish Embassy"
actor_reqs    =
    { "type",   "name", "range"
      "UnitState", "OnLivableTile", "Local"
      "MinMoveFrags", "1", "Local"
    }
target_reqs  =
    { "type",   "name", "range", "present"
      "NationGroup", "Barbarian", "Player", FALSE
    }

Investigate City

To have city investigation be restricted the way it used to be with hardcoded rules, add action enabler like this:

[actionenabler_investigate_city]
action       = "Investigate City"
actor_reqs    =
    { "type",   "name", "range"
      "UnitFlag", "Diplomat", "Local"
      "UnitState", "OnLivableTile", "Local"
      "MinMoveFrags", "1", "Local"
    }

Steal Tech

Tech stealing has implemented as two different actions in action enablers framework. One is the kind of tech stealing where user decides tech to steal, the other one tries to steal random one. To have them restricted the way it used to be with hardcoded rules, add action enablers like this:

[actionenabler_steal_tech_random]
action = "Steal Tech"
actor_reqs    =
    { "type",   "name", "range", "present"
      "UnitFlag", "Spy", "Local", FALSE
      "UnitState", "OnLivableTile", "Local", TRUE
      "MinMoveFrags", "1", "Local", TRUE
    }
target_reqs  =
    { "type",   "name", "range", "present"
      "NationGroup", "Barbarian", "Player", FALSE
    }

[actionenabler_steal_tech_target]
action = "Targeted Steal Tech"
actor_reqs    =
    { "type",   "name", "range"
      "UnitFlag", "Spy", "Local"
      "UnitState", "OnLivableTile", "Local"
      "MinMoveFrags", "1", "Local"
    }
target_reqs  =
    { "type",   "name", "range", "present"
      "NationGroup", "Barbarian", "Player", FALSE
    }

Establish Trade Route

To have trade route establishing be restricted the way it used to be with hardcoded rules, add action enabler like the following. This assumes you have user unit flag TradeRoute defined.

[actionenabler_traderoute]
action       = "Establish Trade Route"
actor_reqs    =
    { "type",   "name", "range"
      "UnitFlag", "TradeRoute", "Local"
    }

Enter Marketplace

To have entering marketplace be restricted the way it used to be with hardcoded rules, add action enabler like the following. This assumes you have user unit flag TradeRoute defined.

[actionenabler_marketplace]
action       = "Enter Marketplace"
actor_reqs    =
    { "type",   "name", "range"
      "UnitFlag", "TradeRoute", "Local"
    }

Help Wonder

To have Wonder building helping be restricted the way it used to be with hardcoded rules, add action enabler like the following. This assumes you have user unit flag HelpWonder defined.

[actionenabler_help_wonder]
action       = "Help Wonder"
actor_reqs    =
    { "type",   "name", "range", "present"
      "UnitFlag", "HelpWonder", "Local", TRUE
      "DiplRel", "Is foreign", "Local", FALSE
    }

New in 2.6

The brand new action "Steal Gold" has been added. It didn't exist in 2.5. It is completely optional. To keep 2.5 behavior you shouldn't enable it at all.

Forcing Trade Routes to get established

By default "Enter Marketplace" action is available even when there would be still free trade route slots to establish one. To force old behavior of automatically establishing trade route if possible, and entering marketplace only if it's not possible, set new actions.force_trade_route in game.ruleset to TRUE.

Buildings obsolescence

Normal Buildings and Small Wonders can get obsolete by means other than their owner gaining certain tech, and Great Wonders means other than anyone in the whole world gaining certain tech. Building obsolete_by is now requirement vector, with any one of the listed requirements being true obsoleting the building. To recreate old behavior, add player range tech requirement for normal buildings and Small Wonders, and world range tech req with "survives" flag for Great Wonders.

For example for a Great Wonder:

obsolete_by     = "Electricity"

->

obsolete_by     =
    { "type", "name", "range", "survives"
      "Tech", "Electricity", "World", TRUE
    }

Building replacement

Buildings no longer have replaced_by field, but such an replacing building should be added as one of the obsolete_by requirements.

Barracks:

obsolete_by = "Gunpowder"

->

obsolete_by =
  { "name", "type", "range"
    "Tech", "Gunpowder", "Player"
  }

Oracle:

obsolete_by = "Theology"

->

obsolete_by =
  { "name", "type", "range"
    "Tech", "Theology", "World"
  }

Revolution Unhappiness

Boolean Revolution_When_Unhappy effect replaced with Revolution_Unhappiness effect. It's value defines how many turns city can be in disorder before the nation revolts. Value 0 disables such revolutions completely. Old hardcoded count of turns was 2, so usually you can recreate that situation by replacing Revolution_When_Unhappy effects Revolution_Unhappiness effect with value 2. If you had multiple such effects possibly being active at the same time, be careaful to use nreqs if you don't want values (i.e. count of turns) from multiple effects to sum up.

Unit bribe cost

Unit bribe cost can be modified by effect Unit_Bribe_Cost_Pct. This effect is also used to get rid of old hardcoded rule that city founder units are 50% cheaper to bribe. If you want to keep that old rule, add effect like:

[effect_unit_bribe_cost_settlers]
type    = "Unit_Bribe_Cost_Pct"
value   = -50
reqs    =
    { "type", "name", "range"
      "UnitFlag", "Cities", "Local"
    }

Unbribable flag

Hardcoded unit type flag Unribable has been removed. You need to define it as user unit flag if you have units that have it, and you need to make unit bribing action enabler to require target not to have it.

Unbribable_Units effect

The Unbribable_Units effect has been removed. Use not present requirements in the target requirement vector in Bribe Unit action enablers in stead.

No_Incite effect

The No_Incite effect has been removed. Use present = FALSE requirements in the target requirement vector in Incite City action enablers in stead.

Achievements

Achievements are new feature in 2.6. You can define them in game.ruleset, but that's optional and to keep old 2.5 behavior you should not add any achievements.

Animals

Animals are new barbarian type. To keep old behavior of not having them, one simply does not define special nation for them. However, following changes to rulesets needs to be done.

Animals for terrains

Field animal should be added for all terrain types. That's unit type that would appear as animal on that terrain. For old behavior of not having animals one can simply use special value None for all of them.

Tech tree holes

You need to add booleans tech_steal_allow_holes, tech_trade_allow_holes, tech_parasite_allow_holes, tech_trade_loss_allow_holes, and tech_loss_allow_holes to research -section of game ruleset to define in which situations one may get a tech for which prerequisites are not known, or lose one which is prerequisite for another known tech. Old hardcoded rules allowed any available tech to be gained/lost in all of these situations, so to mimic that you should set them all to TRUE.

Research values in [research]

All the research related values in game.ruleset have been moved to [research] section. The values to move are tech_cost_style, base_tech_cost, and tech_leakage.

Technology cost and technology leakage methods are now defined by descriptive words instead of magic numbers. Here the conversion tables between old and new values:

Freeciv 2.5	Freeciv 2.6
tech_cost_style = 0	tech_cost_style = "Civ I|II"
tech_cost_style = 1	tech_cost_style = "Classic"
tech_cost_style = 2	tech_cost_style = "Classic+"
tech_cost_style = 3	tech_cost_style = "Experimental"
tech_cost_style = 4	tech_cost_style = "Experimental+"

Freeciv 2.5	Freeciv 2.6
tech_leakage = 0	tech_leakage = "None"
tech_leakage = 1	tech_leakage = "Embassies"
tech_leakage = 2	tech_leakage = "All Players"
tech_leakage = 3	tech_leakage = "Normal Players"

Terrain and Resource Names

All references to other resources and terrains in terrain.ruleset must be changed to use their rule_name instead of old practice of using the name of the section where the terrain or resource is defined.

National styles

Old city_style has been replaced by three-part hierarchy. Each nation has a style. Each city has city_style that's usually (but not necessarily) derived from the national style by using it as requirement. There's also music_style that controls what kind of music client of the player should play. This too can require certain national style. Styles are defined in new ruleset styles.ruleset For recreating exactly same kind of city_styles as ruleset used to have in 2.5, you need to create one national style for each initial (those which were not replaced_by of any other) city_style, and to make those initial city_styles to require equivalent national style.

National Styles

Add necessary [style_xxx] definitions to styles.ruleset. For each nation, unless you are using default ones from freeciv distribution, you need to replace old city_style -entry with style -entry. If you have named national styles in styles.ruleset to have the same name as the initial city style enabled by it, all you need to do is to replace word city_style with style. Similarly in nations ruleset [compatibility] section allowed_city_styles must be replaced with allowed_styles.

City Styles

Move city style definitions from cities.ruleset to styles.ruleset. Remove now unused replaced_by field. Make sure the city styles are in correct order. Last for which requirements are fulfilled, will be used. If you had separate gfx for oceanic cities, you now need to define those oceanic cities as separate city styles, by having requirement like "TerrainClass", "Oceanic", "Local". Make sure the order of city styles is correct, or also add requirement like "TerrainClass", "Land", "Local" for land city styles, so that the land style does not get selected for oceanic cities too. Remove oceanic_graphic definitions from all the city styles.

Music Styles

Add at least one music style definition to styles.ruleset. If you are building entire modpack with ruleset, tileset, and soundset, you may want to add also musicset now.

Traderoutes

New types

Old IN (International) and INIC (International & Intercontinental) traderoute types have been split to more types depending on the diplomatic relations between the nations doing the trade. Ally and AllyIC apply to trade between allied players. Enemy and EnemyIC apply to trade between enemies. Team and TeamIC apply to trade between team members. All other relations, including transitional ones such as armistice and cease-fire, still use IN & INIC. To keep old behavior just copy definitions of IN/INIC as Ally/AllyIC, Enemy/EnemyIC, and Team/TeamIC definitions in game.ruleset

One-time bonus definition

Each traderoute type should have bonus type defined. For always receiving both gold and bulb bonus when traderoute is established, like the old hardcoded behavior was, set it to Both for all traderoute types.

ZOC terrains

Hardcoded rule that ZoC is created only by units on Land terrains, as well as limiting only those units, has been replaced with NoZoc terrain flag. To keep old behavior, add the NoZoc flag to all oceanic terrains.

Fortifying

Terrains

Hardcoded rule that units can Fortify only on land terrains, has been replaced with NoFortify terrain flag. To keep old behavior, add the NoFortify flag to all oceanic terrains.

Units

Hardcoded limitation that workers cannot fortify has been removed. New unit type flag Cant_Fortify controls which units cannot fortify despite their class having CanFortify flag. To keep old hardcoded behavior, add Cant_Fortify unit type flag to all units with Settlers flag.

Trait ranges

AI traits are now defined as ranges instead of exact value. Random value from the given range will be assigned to the player when game starts. To keep old exact values, just define range to contain just that one value. Ranges are given by replacing each old trait entry with two; one with suffix "_min" and other with suffix "_max". Both default trait values and nation specific traits need to be changed.

[default_traits]
expansionist = 50
...
[nation_abkhaz]
...
trait_expansionist = 200

->

[default_traits]
expansionist_min = 50
expansionist_max = 50
...
[nation_abkhaz]
...
trait_expansionist_min = 200
trait_expansionist_max = 200

Airlifting

Unit class airliftability is now unit class flag. To keep old hardcoded behavior, give flag Airliftable to all land moving unit classes.

Movement cost

You need to add pythagorean_diagonal entry to [parameters] section of terrain.ruleset, controlling if diagonal movement is more expensive than cardinal movement in square tile maps. To preserve old hardcoded behavior, set it to value FALSE.

Unit move_type obsoleted

Unit move_type definition, already optional in 2.5, for unit types has been completely removed from units.ruleset. Just remove it from all units that still had it.

IgWall unit type flag removed

Hardcoded IgWall unit type flag has been removed. You should add such units as present = FALSE requirements for all Defend_Bonus effects. If you had just one such unit type, you can use UnitType requirement type. If you had several affected unit types, you may want to reintroduce IgWall as user unit type flag and use UnitFlag requirement type.

Culture Victory

You need to add minimum culture settings for culture victory to game.ruleset [culture] section. If you just want to keep the old behavior of game having no culture effects, any positive values will suffice here, as nobody can ever reach over 0 culture points.

[culture]
; Minimum culture points for cultural domination victory
victory_min_points = 1000

; How big lead relative to second best player is needed for victory
victory_lead_pct   = 200

; How much each culture point affects the migration
; from/to the city.
migration_pct = 50

Policies

Policy multipliers are new feature in 2.6. You can define them in governments.ruleset, but that's optional and to keep old 2.5 behavior you should not add any multipliers.

Population pollution

The tech flag "Population_Pollution_Inc" has been replaced by effect "Pollu_Pop_Pct_2".

To continue with existing behaviour, add this base effect:

[effect_pollu_pop_base]
type    = "Pollu_Pop_Pct_2"
value	= -100

and an effect like this for every tech that had the 'Population_Pollution_Inc' flag:

[effect_pollu_pop_automobile]
type    = "Pollu_Pop_Pct_2"
value	= 25
reqs    =
    { "type", "name", "range"
      "Tech", "Automobile", "Player"
    }

(Also you probably want to add a helptext to these techs, since the automatically generated one has gone away.)

Gold Upkeep

Gold upkeep method is now defined by descriptive words instead of magic numbers. Here the conversion table between old and new values:

Freeciv 2.5	Freeciv 2.6
tech_cost_style = 0	tech_cost_style = "City"
tech_cost_style = 1	tech_cost_style = "Mixed"
tech_cost_style = 2	tech_cost_style = "Nation"

World-ranged tech requirement behaviour changed

"Tech" requirements with "World" range no longer implicitly survive every player losing that tech. If you want to preserve the old behavior, you should add an explicit "survives" flag.

   { "type", "name", "range"
     "Tech", "Space Flight", "World"
   }

->

   { "type", "name", "range", "survives"
     "Tech", "Space Flight", "World", TRUE
   }

Barbarian unit retirement

There is no longer hardcoded barbarian unit retirement. To recreate the barbarian unit retirement and barbarian leader escape, Retire_Pct effects can be used. Below example assumes that both barbarians have also been put to single Barbarian NationGroup. Otherwise one would need separate effects for both Barbarian and Pirate nations

[effect_barb_disappear]
type    = "Retire_Pct"
value   = 10
reqs    =
    { "type", "name", "range", "present"
      "NationGroup", "Barbarian", "Player", TRUE
      "Age", "5", "Local", TRUE
      "CityTile", "Center", "Local", FALSE
    }

; Lone Leader might escape on coast (33% chance)
; Complement of the two effects should be 0.9 * 0.66 = 0.594
; (100 - 59) - 10 = 31
[effect_leader_escape]
type    = "Retire_Pct"
value   = 31
reqs    =
    { "type", "name", "range"
      "UnitType", "Barbarian Leader", "Local"
      "Age", "5", "Local"
      "TerrainClass", "Oceanic", "Adjacent"
      "MaxUnitsOnTile", "1", "Local"
    }

Calendar fragments

New calendar related definitions need to be added for sub-year turns. To keep using full years, just set fragments in game.ruleset [calendar] to 0.

Cost of illegal actions

If diplomat or caravan fail to execute their orders due to reasons player was not aware beforehand, attempt may cause them movement points. This cost is no longer hardcoded to 1 movement point, but it's controlled by Illegal_Action_Move_Cost effect. To have old one movement point cost for any failing order, add effect like:

[effect_illegal_action_cost]
type    = "Illegal_Action_Move_Cost"
value   = 1

Barbarian Nations

Barbarian NationGroup

Default nationlist.ruleset now has hidden NationGroup Barbarian and included barbarian nations belong to that group. If you use these, you now may simplify effects written separately for each barbarian nation to be combined to single one where requirement NationGroup Barbarian is used instead of Nation requirements.

Barbarian Nations to be included separately

Default nationlist.ruleset no longer contains any barbarian nations. You need to include them directly to your nations.ruleset.

*include "nation/barbarian.ruleset"
*include "nation/pirate.ruleset"

Remember to set embedded_nations accordingly:

embedded_nations = "barbarian", "pirate"

Incite cost of empty cities

Hardcoded rule that incite cost is halved for empty cities has been removed. One can have the same rule via Incite_Cost_Pct effects with MaxUnitsOnTile 0 requirement.

[effect_incite_cost_empty]
type = "Incite_Cost_Pct"
value = -50
reqs    =
    { "type", "name", "range", "present"
      "MaxUnitsOnTile", "0", "Local", TRUE
    }

Borders claimed by cities

With the adjustments to border claiming rules new field, radius_sq_city_permanent, is required in game.ruleset. Set it to value 0 to keep old behavior.

Caravan unit type flags unhardcoded

There is no longer hardcoded flags TradeRoute or HelpWonder. Define them as user unit type flags if you need them in your trade route or help wonder action enablers.

UI strings

Action Names

You should define UI names of the diplomat and caravan actions your ruleset is using in game.ruleset actions -section. See classic ruleset for the list of traditional actions.

Base building commands by gui_type

You should provide extraui -section to terrain.ruleset with entries to show in the UI for the commands to build any base by their gui_type; Fortress or Airbase.

[extraui]
; Player visible names of the base gui types.
ui_name_base_fortress = _("?gui_type:Build Land base")
ui_name_base_airbase = _("?gui_type:Build Airforce base")