anchor.diff:  
                   let testScreenAddress = [Lun.make "testScreen"]
                   let testGroupAddress = testScreenAddress @ [Lun.make "testGroup"]
  -                let testFeelerAddress = testGroupAddress @ [Lun.make "testFeeler"]
                   let testTextBoxAddress = testGroupAddress @ [Lun.make "testTextBox"]
   
                   let testScreen =
  
positive.code:                 form.exitToolStripMenuItem.Click.Add (fun _ -> form.Close ())
                  form.Show ()
                  Right refWorld.Value)
          (fun world ->
              // NOTE: the old refWorld will be blown away here!
              refWorld := applyEntityChanges gEntityChanges world
  
negative.code:     override this.GetTypeDescriptor (_, _) = Etd
  
  let [<EntryPoint; STAThread>] main _ =
      use form = new NuEditForm ()
      let sdlViewConfig = ExistingWindow form.displayPanel.Handle
      let sdlRenderFlags = enum<SDL.SDL_RendererFlags> (int SDL.SDL_RendererFlags.SDL_RENDERER_ACCELERATED ||| int SDL.SDL_RendererFlags.SDL_RENDERER_PRESENTVSYNC)
      let sdlConfig = makeSdlConfig sdlViewConfig 900 600 sdlRenderFlags 1024
      let refWorld = ref Unchecked.defaultof<World>
      run4
          (fun sdlDeps ->
  
  