anchor.diff:                  | None -> world
               | _ -> failwith <| "Invalid group address '" + acstring address + "'."
   
  -        static member private getGroupMapInScreen screenRep world =
  +        static member internal getGroupMapInScreen screenRep world =
               match screenRep.ScreenAddress.Names with
               | [screenName] ->
                   let (_, screenMap) = world.Simulants
  
positive.code:           OverlayRouter : OverlayRouter
            OverlayFilePath : string
            UserState : obj }
  
      /// The world, in a functional programming sense. Hosts the game object, the dependencies
      /// needed to implement a game, messages to by consumed by the various engine sub-systems,
  
negative.code:                     world
              else world
  
          static member internal updateScreen updater screenRep world =
              let screen = World.getScreen screenRep world
              let screen = updater screen
              World.setScreen screen screenRep world
  
          static member private registerScreen (screenRep : ScreenRep) world =
              let dispatcher = screenRep.GetDispatcherNp world : ScreenDispatcher
              dispatcher.Register screenRep world
  
          static member private unregisterScreen (screenRep : ScreenRep) world =
              let dispatcher = screenRep.GetDispatcherNp world : ScreenDispatcher
              dispatcher.Unregister screenRep world
  
          static member private addScreen screenHierarchy screenRep world =
              let (screen, groupHierarchies) = screenHierarchy
              if not <| World.containsScreen screenRep world then
                  let world = World.setScreenWithoutEvent screen screenRep world
                  let world = World.addGroups groupHierarchies screenRep world
                  let world = World.registerScreen screenRep world
                  World.publish4 () (World.ScreenAddEventAddress ->>- screenRep.ScreenAddress) screenRep world
              else failwith <| "Adding a screen that the world already contains at address '" + acstring screenRep.ScreenAddress + "'."
  
          /// Query that the world contains a group at the given address.
          static member containsScreen screenRep world =
              Option.isSome <| World.optScreenFinder screenRep.ScreenAddress world
  