Added player research scaling

config.lua

@@ -340,6 +340,14 @@ global.config = {
     player_onboarding = {
         enabled = true
     },
+    -- increases technology price multiplier with number of connected players
+    research_scaling = {
+        enabled = false,
+        -- the increase in the multiplier with every player
+        scale_value = 0.05,
+        -- max increase in research price multiplier (-1 for disabled)
+        limit = -1
+    },
     -- allows for large-scale biter attacks
     biter_attacks = {
         enabled = true,

control.lua

@@ -133,6 +133,9 @@ end
 if config.rich_text_gui.enabled then
     require 'features.gui.rich_text'
 end
+if config.research_scaling.enabled then
+    require 'features.research_scaling'
+end
 
 -- Debug-only modules
 if _DEBUG then

features/research_scaling.lua

@@ -0,0 +1,48 @@
+---Scales technology price multiplier based on number of online players.
+---It does so only when finished research
+local Event = require 'utils.event'
+local Global = require 'utils.global'
+
+local config = global.config.research_scaling
+local limit = config.limit
+local scale_value = config.scale_value
+
+local multipliers = {
+    current_multiplier = 0,
+    old_multiplier = 0,
+    old_setting = 0
+}
+
+Global.register(
+    {
+        multipliers = multipliers
+    },
+    function(tbl)
+        multipliers = tbl.multipliers
+    end
+)
+
+local function update_research_cost()
+    local player_count = #game.connected_players
+    local setting = game.difficulty_settings.technology_price_multiplier
+    local modifier = player_count * scale_value - scale_value
+    -- if config.limit is enabled, make sure the modifier doesn't exceed the limit
+    if limit ~= -1 then
+        modifier = (modifier <= limit) and modifier or limit
+    end
+
+    -- keeping track of old and new multiplier
+    multipliers.old_multiplier = multipliers.current_multiplier
+    multipliers.current_multiplier = modifier
+
+    -- setting new modifier by subtracting old multiplier from setting and adding the new
+    if setting == multipliers.old_setting then
+        modifier = setting - multipliers.old_multiplier + modifier
+    else -- if the setting was changed in between add the modifier a new.
+        modifier = setting + modifier
+    end
+    game.difficulty_settings.technology_price_multiplier = modifier
+    multipliers.old_setting = modifier
+end
+
+Event.add(defines.events.on_research_finished, update_research_cost)