CatServer/patches/net/minecraft/client/gui/GuiCreateWorld.java.patch

--- ../src-base/minecraft/net/minecraft/client/gui/GuiCreateWorld.java
+++ ../src-work/minecraft/net/minecraft/client/gui/GuiCreateWorld.java
@@ -206,6 +206,8 @@
                     }
                 }
 
+                WorldType.WORLD_TYPES[this.selectedIndex].onGUICreateWorldPress();
+
                 WorldSettings worldsettings = new WorldSettings(i, GameType.getByName(this.gameMode), this.generateStructuresEnabled, this.hardCoreMode, WorldType.WORLD_TYPES[this.selectedIndex]);
                 worldsettings.setGeneratorOptions(this.chunkProviderSettingsJson);
 
@@ -312,14 +314,7 @@
             }
             else if (button.id == 8)
             {
-                if (WorldType.WORLD_TYPES[this.selectedIndex] == WorldType.FLAT)
-                {
-                    this.mc.displayGuiScreen(new GuiCreateFlatWorld(this, this.chunkProviderSettingsJson));
-                }
-                else
-                {
-                    this.mc.displayGuiScreen(new GuiCustomizeWorldScreen(this, this.chunkProviderSettingsJson));
-                }
+                WorldType.WORLD_TYPES[this.selectedIndex].onCustomizeButton(mc, this);
             }
         }
     }
@@ -379,7 +374,7 @@
             this.btnBonusItems.visible = this.inMoreWorldOptionsDisplay;
             this.btnMapType.visible = this.inMoreWorldOptionsDisplay;
             this.btnAllowCommands.visible = this.inMoreWorldOptionsDisplay;
-            this.btnCustomizeType.visible = this.inMoreWorldOptionsDisplay && (WorldType.WORLD_TYPES[this.selectedIndex] == WorldType.FLAT || WorldType.WORLD_TYPES[this.selectedIndex] == WorldType.CUSTOMIZED);
+            this.btnCustomizeType.visible = this.inMoreWorldOptionsDisplay && WorldType.WORLD_TYPES[this.selectedIndex].isCustomizable();
         }
 
         this.updateDisplayState();