anchor.diff:      | _ -> failwith ("Expected MouseButtonData from address '" + str address + "'.")
       
   let registerFeeler address world =
  -    let optOldFeeler = get world (World.optFeeler address)
  -    let world_ = if optOldFeeler.IsSome then unregisterFeeler address world else world
  -    let world_ = subscribe DownMouseLeftAddress address handleFeelerEventDownMouseLeft world_
  -    subscribe UpMouseLeftAddress address handleFeelerEventUpMouseLeft world_
  +    let world2 = subscribe DownMouseLeftAddress address handleFeelerEventDownMouseLeft world
  +    subscribe UpMouseLeftAddress address handleFeelerEventUpMouseLeft world2
   
   let addFeeler address feeler world =
       let world2 = registerFeeler address world
  
positive.code:     | _ -> failwith ("Expected MouseButtonData from address '" + str address + "'.")
  
  let registerToggle address world =
      let optOldToggle = get world (World.optToggle address)
      let world_ = if optOldToggle.IsSome then unregisterToggle address world else world
      let world_ = subscribe DownMouseLeftAddress address handleToggleEventDownMouseLeft world_
      subscribe UpMouseLeftAddress address handleToggleEventUpMouseLeft world_
  
  let addToggle address toggle world =
      let world2 = registerToggle address world
  
negative.code:         let w_ = unsubscribe TickAddress [] w_
          let w_ = unsubscribe ClickButtonAddress [] w_
          let w_ = set None w_ World.optActiveScreenAddress
          let w_ = removeEntityModelsFromGroup address w_
          set None w_ (World.optGroupModel address)
  
  