In OpenXcom a ruleset is an easy to edit text file that contains settings (rules) that describe almost everything about how the game operates. Here are just some of the things that are in the ruleset:
The costs, stats and characteristics of all items, units, facilities, X-COM craft and UFOs
Dependencies and costs for research, manufacture and UFOpedia
Your starting base
The costs of personnel and transfer time.
The stats of the funding countries and regions of the world.
You can find the rulesets in your Data\Ruleset folder.
Editing Rulesets (YAML)
Notepad++ Settings for editing OpenXcom YAML files
OpenXcom exposes its inner workings to users and modders in the form of YAML text files. Although YAML can be edited with any text editor, such as Notepad, it is much easier to use a dedicated YAML editor. YAML has a special syntax so any incorrect whitespace or character can cause an error, but it's a simple human-readable format so you should be able to figure it out by looking at the existing rulesets.
Notepad++
You can open any rulesets (or savegame files) in Notepad++ and select Language>YAML. This will help you keep the proper tabbing structure and also allow you to collapse large regions. You can set Notepad++ to recognize *.rul, *.sav and *.cfg files as YAML file extensions under preferences so that you don't have to set the language every time you edit one of OpenXcom's files.
Can't Notepad++?
Alternatively you could conjure up a Google search and look for YAML editors that are compatible with your OS. There are YAML plugins for both Visual Studio and Eclipse. Yedit for Eclipse is popular.
Note: You should be able to collapse regions in whatever YAML editor you use. If not, you're in for a lot of scrolling as the files are quite large.
Your First Edit (Cheat)
Open the Data\Ruleset\Xcom1Ruleset.rul file in your YAML editor.
Collapse everything (Alt-0 in Notepad++) and then open (uncollapse) the "facilities:" section.
Open "- type: STR_LIVING_QUARTERS"
change "personnel: 50" to "personnel: 500"
Congratulations! You can now have 500 personal per living quarters.
A couple other examples
1. Fusion Ball Launcher balance update: Let's make something other than plasma cannons useful
change "craftWeapons:" -> "type: STR_PLASMA_BEAM_UC>" -> "range: 52" to "range: 40" (just inside a terror-ships range)
set the range for Laser Cannons to 34 (same as large scout) and set Stingray and avalanche ranges even shorter
Now there's a reason to build Fusion-Ball Launchers - shoot down Battleships and Terrorships, there's also a reason for Plasma Beams - shoot down Supply Ships and Large Scouts without getting hit, and a reason for Laser Cannons - shoot down Harvesters or Abductors safely and shoot down Large Scouts at equal range.
2. Sectopod Buff: It's time to put the fear of Sectopod in those power-suit/hovertank squads that think Ethereal Terrorsites are some kind of joke!
"units:" -> "- type: STR_SECTOPOD_TERRORIST" -> "stats:" set TUs to 110, stamina to 125, Firing Accuracy to 100, Psi-Strength to 160 and health to 135.
Note the field "armor: SECTOPOD_ARMOR". So close "units:" and open "armors:" -> "type: SECTOPOD_ARMOR"
Set rear armor to 130 (a sectopod has a finely armored buttox, thankyou).
Open "damageModifier:" (its part of the armor) and find a "- 1.5" and a "- 0.8" just below it. These are the values for how much damage a unit wearing sectopod armor takes from laser(1.5x) and plasma(0.8x). Increase the laser bonus to 1.8 and reduce the plasma further to 0.65 (it's now actually worth it to bring laser weapons just for the sectopods)
Close "armors:" and open "items:" -> "type: SECTOPOD_WEAPON" and let's give it a good 145 weapon power. No need to adjust the weapon accuracy since we already increased the stat.
Now you can go back to having nightmares about Sectopods, just like you did when you were a young child who got in trouble for playing X-COM on the family computer after bed-time when you hadn't even done your homework.
3. Early Blaster: The best time to have a Blaster Launcher is in the back of a Skyranger full of rookies.
Go to "items:" and pick anything that's purchasable. Copy the line with "costBuy:" and a number. Make sure you copy the tabs before "costBuy:". The best way to do this is to put the cursor at the end of the line above it, shift-down-arrow and shift-end to select the entire line and the line-break characters.
Go to "type: STR_BLASTER_LAUNCHER" and add the "costBuy:" line. If the new line your adding doesn't look like the other lines in your YAML editor (like if it's red or black text instead of blue) then it's probably wrong and you probably have incorrect tab or line-break characters in it.
Remove the section "required:"
Do the last two things for Blaster Bombs as well.
Open "startingBase:" -> "lon: 0.0" -> "items:" and replace "STR_CANNON" and "STR_CANNON_ROUNDS_X50" with "STR_BLASTER_BOMB" and "STR_BLASTER_LAUNCHER"
Start a new game, load up blasters on your skyranger, and land by a medium scout. Now hit the side of the medium scout with one shot to make a hole, hit that silly glowy thing in the middle with the second shot. Voilà, that rookie killing death-trap is now just like a crash-site, except with even less live aliens inside.
A reference of all the customizable values of everything in a ruleset. Some guidelines:
If a value is omitted from the ruleset, the default is used. You cannot omit required values.
Text strings (eg. names) are represented by string IDs from the [Translations (OpenXcom)|language files]
Numerical IDs (used for sprites, sounds, etc.) start at 0, not 1.
Boolean (yes/no) values are represented by true/false.
World coordinates are represented in degrees (see WORLD.DAT).
Money amounts (prices, costs, etc.) are represented in dollars.
Countries
Defines one of the funding nations, listed in "countries:". They're used for activity graphs and player scoring.
Value
Description
Default
type
String ID of the country name.
required
fundingBase
The country's base funding, in thousands. The starting funding can be anywhere between 1x and 2x the base funding.
0
fundingCap
The country's funding cap, in thousands. Once a country reaches this maximum, it will no longer increase its funding.
0
labelLon
labelLat
The longitude and latitude of the country's label on the globe. This label is only shown when the globe is zoomed in and "detail" is turned on.
0.0
0.0
areas
A list of "square areas" on the globe defined as [lon1lat1lon2lat2]. Any activity within these areas counts towards the country's graph activity and affects their opinion of the player.
-
Regions
Defines one of the world regions, listed in "regions:". They're used for base placement, activity graphs and mission spawning.
Value
Description
Default
type
String ID of the region name.
required
cost
Total cost for placing an X-COM base in this region.
0
areas
A list of "square areas" on the globe defined as [lon1, lat1, lon2, lat2]. Any activity within these areas counts towards the region's graph activity.
-
cities
A list of cities belonging to this region. They will be displayed on the globe and used for terror site missions. Each city is defined by their lon and lat coordinates and a name string ID.
-
regionWeight
Weight of this region when selecting regions for alien missions.
0
missionWeights
Weighted list of the different mission types for this region (eg. STR_ALIEN_RESEARCH: 14).
-
missionZones
List of square areas ([lon1, lat1, lon2, lat2]) defining the mission zones for this region.
-
missionRegion
Spawn mission in this region instead (used for regions without land).
-
Base Facilities
Defines one of the facilities that can be built in an X-COM base.
Value
Description
Default
type
String ID of the facility name.
required
requires
List of topics (string IDs) that must be researched to unlock this facility.
-
spriteShape
Sprite ID from BASEBITS.PCK used to draw the facility's outer shape in the Basescape and UFOpaedia.
-1
spriteFacility
Sprite ID from BASEBITS.PCK used to draw the facility's contents in the Basescape and UFOpaedia. Drawn on top of spriteShape.
lift
Is this facility an Access Lift? All base facilities must be connected to the lift.
false
hyper
Is this facility a Hyperwave Decoder? Displays extra information for detected UFOs. Only valid for radar facilities.
false
mind
Is this facility a Mind Shield? Reduces the chance of UFOs finding your base. Does not stack.
false
grav
Is this facility a Grav Shield? Doubles the power of your base defenses. Does not stack.
false
size
Size of the facility, in grid units. Every facility is square, so a size of 1 means 1x1, 2 means 2x2, etc. Bigger facilities are made up of multiple sprites, for example a 2x2 facility will use 4 sprites for spriteShape and 4 sprites for spriteFacility (top-left, top-right, bottom-left, bottom-right).
1
buildCost
The cost it takes to build this facility on the base.
0
buildTime
The amount of days it takes for this facility to be built.
0
monthlyCost
The monthly maintenace cost for this facility.
0
storage
The amount of storage space (for items) this facility provides. See Base Stores.
0
personnel
The amount of personnel (soldiers, scientsts, engineers) these quarters can contain.
0
aliens
The amount of live aliens this facility can contain. Only checked if the alienContainmentLimitEnforced option is enabled.
0
crafts
The amount of X-COM craft this facility can contain.
0
labs
The amount of lab space this facility provides for research projects.
0
workshops
The amount of workshop space this facility provides for manufacture projects.
0
psiLabs
The amount of soldier space this facility provides for psionic training.
0
radarRange
The maximum radar detection range of this facility, in nautical miles.
0
radarChance
The chance (0-100%) of this radar detecting a UFO that enters its range.
0
defense
The offensive power this base defense provides against attacking UFOs.
0
hitRatio
The chance (0-100) of the base defense hitting an attacking UFO.
0
fireSound
Sound ID (from SAMPLE.CAT) played when the base defense fires.
-1
hitSound
Sound ID (from SAMPLE.CAT) played when the base defense hits a target.
-1
mapName
The name of the map associated to this facility in Battlescape base defenses.
