Better proguard rules to enable r8 minification

android/proguard-rules.pro

@@ -26,8 +26,18 @@
 -dontwarn com.badlogic.gdx.utils.GdxBuild
 -dontwarn com.badlogic.gdx.jnigen.BuildTarget*
 
--keep class com.badlogic.gdx.controllers.android.AndroidControllers
-
 -keepclassmembers class com.badlogic.gdx.backends.android.AndroidInput* {
    <init>(com.badlogic.gdx.Application, android.content.Context, java.lang.Object, com.badlogic.gdx.backends.android.AndroidApplicationConfiguration);
 }
+
+# You will need the next three lines if you use scene2d for UI or gameplay.
+# If you don't use scene2d at all, you can remove or comment out the next line:
+-keep public class com.badlogic.gdx.scenes.scene2d.** { *; }
+# You will need the next two lines if you use BitmapFont or any scene2d.ui text:
+-keep public class com.badlogic.gdx.graphics.g2d.BitmapFont { *; }
+# You will probably need this line in most cases:
+-keep public class com.badlogic.gdx.graphics.Color { *; }
+
+# These two lines are used with mapping files; see https://developer.android.com/build/shrink-code#retracing
+-keepattributes LineNumberTable,SourceFile
+-renamesourcefileattribute SourceFile

core/src/com/unciv/ui/screens/newgamescreen/IPreviousScreen.kt

@@ -10,7 +10,7 @@ import com.unciv.models.ruleset.Ruleset
  */
 interface IPreviousScreen {
     val gameSetupInfo: GameSetupInfo
-    var stage: Stage
+    val stage: Stage
     val ruleset: Ruleset
 
     // Having `fun setRightSideButtonEnabled(boolean: Boolean)` part of this interface gives a warning: