anchor.diff:  open Nu.Game
   open Nu.Simulation
   
  -let TestScreenAddress = [Lun.make "testScreen"]
  -let TestGroupAddress = TestScreenAddress @ [Lun.make "testGroup"]
  -let TestFeelerAddress = TestGroupAddress @ [Lun.make "testFeeler"]
  -let TestTextBoxAddress = TestGroupAddress @ [Lun.make "testTextBox"]
  -let TestToggleAddress = TestGroupAddress @ [Lun.make "testToggle"]
  -let TestLabelAddress = TestGroupAddress @ [Lun.make "testLabel"]
  -let TestButtonAddress = TestGroupAddress @ [Lun.make "testButton"]
  +let TestScreenAddress = [Lun.make "screen"]
  +let TestGroupAddress = TestScreenAddress @ [Lun.make "group"]
  +let TestFeelerAddress = TestGroupAddress @ [Lun.make "feeler"]
  +let TestTextBoxAddress = TestGroupAddress @ [Lun.make "textBox"]
  +let TestToggleAddress = TestGroupAddress @ [Lun.make "toggle"]
  +let TestLabelAddress = TestGroupAddress @ [Lun.make "label"]
  +let TestButtonAddress = TestGroupAddress @ [Lun.make "button"]
   let TestBlockAddress = TestGroupAddress @ [Lun.make "testBlock"]
  -let TestTileMapAddress = TestGroupAddress @ [Lun.make "testTileMap"]
  -let TestFloorAddress = TestGroupAddress @ [Lun.make "testFloor"]
  -let TestAvatarAddress = TestGroupAddress @ [Lun.make "testAvatar"]
  -let TouchFeelerAddress = Lun.make "touch" :: TestFeelerAddress
  +let TestTileMapAddress = TestGroupAddress @ [Lun.make "tileMap"]
  +let TestFloorAddress = TestGroupAddress @ [Lun.make "floor"]
  +let TestAvatarAddress = TestGroupAddress @ [Lun.make "avatar"]
   let ClickTestButtonAddress = Lun.make "click" :: TestButtonAddress
   
   let createTestBlock assetMetadataMap =
  
positive.code:         let playSong = PlaySong { Song = { SongAssetName = Lun.make "Song"; PackageName = Lun.make "Misc"; PackageFileName = "AssetGraph.xml" }; FadeOutCurrentSong = true }
  
          // scripting convention
          let tw_ = testWorld
          let tw_ = subscribe TickAddress [] moveAvatar tw_
          let tw_ = subscribe ClickTestButtonAddress [] addBoxes tw_
          let tw_ = addScreen testScreen TestScreenAddress tw_
          let tw_ = setP (Some TestScreenAddress) World.optActiveScreenAddress tw_
          let tw_ = addGroup testGroup TestGroupAddress tw_
          let tw_ = addEntityGuiFeeler (testFeelerGuiEntity, testFeelerGui, testFeeler) TestFeelerAddress tw_
          let tw_ = addEntityGuiTextBox (testTextBoxGuiEntity, testTextBoxGui, testTextBox) TestTextBoxAddress tw_
          let tw_ = addEntityGuiToggle (testToggleGuiEntity, testToggleGui, testToggle) TestToggleAddress tw_
          let tw_ = addEntityGuiLabel (testLabelGuiEntity, testLabelGui, testLabel) TestLabelAddress tw_
          let tw_ = addEntityGuiButton (testButtonGuiEntity, testButtonGui, testButton) TestButtonAddress tw_
          let tw_ = addEntityActorTileMap (testTileMapActorEntity, testTileMapActor, testTileMap) TestTileMapAddress tw_
          let tw_ = addEntityActorBlock (testFloorActorEntity, testFloorActor, testFloor) TestFloorAddress tw_
          let tw_ = addEntityActorAvatar (testAvatarActorEntity, testAvatarActor, testAvatar) TestAvatarAddress tw_
          let tw_ = { tw_ with PhysicsMessages = SetGravityMessage Vector2.Zero :: tw_.PhysicsMessages }
          let tw_ = { tw_ with RenderMessages = hintRenderingPackageUse :: tw_.RenderMessages }
          Right { tw_ with AudioMessages = FadeOutSong :: playSong :: tw_.AudioMessages }
  
  let testHandleUpdate world =
      let (_, actor, _) = get world (World.entityActorAvatar TestAvatarAddress)
  
negative.code:     | Left errorMsg -> Left errorMsg
      | Right assetMetadataMap ->
  
          let game =
              { Id = getNuId ()
                Screens = Map.empty
                OptActiveScreenAddress = None }
      
          let world =
              { Game = game
                Camera = { EyePosition = Vector2.Zero; EyeSize = Vector2 (single sdlDeps.Config.ViewW, single sdlDeps.Config.ViewH) }
                Subscriptions = Map.empty
                MouseState = { MousePosition = Vector2.Zero; MouseLeftDown = false; MouseRightDown = false; MouseCenterDown = false }
  