anchor.diff:                              let messageOpt = binding.MakeValueOpt evt
                               match messageOpt with
                               | Some message ->
  -                                let (model, effectOpt) = this.Message (message, model, screen, world)
  +                                let (model, commands) = this.Message (message, model, screen, world)
                                   let world = property.Set model world
  -                                match effectOpt with
  -                                | Some effect ->
  +                                List.fold (fun world command ->
                                       let model = property.Get world
  -                                    this.Effect (effect, model, screen, world)
  -                                | None -> world
  +                                    this.Command (command, model, screen, world))
  +                                    world commands
                               | None -> world)
                               screen binding.Stream world
                       | Effect binding ->
  
positive.code:             let world = World.monitorPlus handleMouseLeft Events.MouseLeftUp gui world |> snd
              world
  
      type [<AbstractClass>] GuiDispatcher<'model, 'message, 'effect> (propertyFn) =
          inherit EntityDispatcher<'model, 'message, 'effect> (propertyFn)
  
          static let handleMouseLeft evt world =
              let gui = evt.Subscriber : Entity
  
negative.code:                             let messageOpt = binding.MakeValueOpt evt
                              match messageOpt with
                              | Some message ->
                                  let (model, commands) = this.Message (message, model, entity, world)
                                  let world = property.Set model world
                                  List.fold (fun world command ->
                                      let model = property.Get world
                                      this.Command (command, model, entity, world))
                                      world commands
                              | None -> world)
                              entity binding.Stream world
                      | Effect binding ->
  