anchor.diff:              this.View (Actualize, model, game, world)
   
           abstract member Binding : 'model * Game * World -> Binding<'message, 'effect, Game, World> list
  -        abstract member Message : 'message * 'model * Game * World -> 'model * (World -> World)
  +        abstract member Message : 'message * 'model * Game * World -> 'model * 'effect option
           abstract member Effect : 'effect * 'model * Game * World -> World
           abstract member View : Phase * 'model * Game * World -> World
positive.code: [<AutoOpen>]
  module ModelViewMessageEffect =
  
      /// Pair an id function with a model.
      let inline just model = (model, id)
  
      /// Specifies the view phase of Nu's MVME form factor.
      type Phase =
  
negative.code:                             let messageOpt = binding.MakeValueOpt evt
                              match messageOpt with
                              | Some message ->
                                  let (model, effectOpt) = this.Message (message, model, game, world)
                                  let world = property.Set model world
                                  match effectOpt with
                                  | Some effect ->
                                      let model = property.Get world
                                      this.Effect (effect, model, game, world)
                                  | None -> world
                              | None -> world)
                              game binding.Stream world
                      | Effect binding ->
  