Add unique to conditionally control construction costs

core/src/com/unciv/models/ruleset/Building.kt

@@ -114,6 +114,9 @@ class Building : RulesetStatsObject(), INonPerpetualConstruction {
         for (unique in getMatchingUniques(UniqueType.CostIncreasesPerCity, stateForConditionals))
             productionCost += civInfo.cities.size * unique.params[0].toInt()
 
+        for (unique in getMatchingUniques(UniqueType.CostPercentageChange, stateForConditionals))
+            productionCost *= unique.params[0].toPercent()
+
         if (civInfo.isCityState())
             productionCost *= 1.5f
         if (civInfo.isHuman()) {

core/src/com/unciv/models/ruleset/unique/UniqueType.kt

@@ -282,6 +282,7 @@ enum class UniqueType(
 
     CostIncreasesPerCity("Cost increases by [amount] per owned city", UniqueTarget.Building, UniqueTarget.Unit),
     CostIncreasesWhenBuilt("Cost increases by [amount] when built", UniqueTarget.Building, UniqueTarget.Unit),
+    CostPercentageChange("[amount]% production cost", UniqueTarget.Building, UniqueTarget.Unit, docDescription = "Intended to be used with conditionals to dynamically alter construction costs"),
 
     @Deprecated("as of 4.10.17", ReplaceWith("Only available <if [buildingFilter] is constructed in all [non-[Puppeted]] cities>"))
     RequiresBuildingInAllCities("Requires a [buildingFilter] in all cities", UniqueTarget.Building),

core/src/com/unciv/models/ruleset/unit/BaseUnitCost.kt

@@ -19,6 +19,9 @@ class BaseUnitCost(val baseUnit: BaseUnit) {
         for (unique in baseUnit.getMatchingUniques(UniqueType.CostIncreasesWhenBuilt, stateForConditionals))
             productionCost += civInfo.civConstructions.builtItemsWithIncreasingCost[baseUnit.name] * unique.params[0].toInt()
 
+        for (unique in baseUnit.getMatchingUniques(UniqueType.CostPercentageChange, stateForConditionals))
+            productionCost *= unique.params[0].toPercent()
+
         if (civInfo.isCityState())
             productionCost *= 1.5f
         productionCost *= if (civInfo.isHuman())

docs/Modders/uniques.md

@@ -1070,6 +1070,12 @@ Simple unique parameters are explained by mouseover. Complex parameters are expl
 
 	Applicable to: Building, Unit
 
+??? example  "[amount]% Cost"
+	Intended to be used with conditionals to dynamically alter construction costs
+	Example: "[3]% Cost"
+
+	Applicable to: Building, Unit
+
 ??? example  "Can only be built [cityFilter]"
 	Example: "Can only be built [in all cities]"