anchor.diff:  
                   // get old world for entity tree rebuild
                   let oldWorld = world
  +
  +                // remove entity from hierarchy
  +                let parentOpt = World.getEntityParentOpt entity world
  +                let world = World.removeEntityFromHierarchy parentOpt entity world
                   
                   // mutate entity tree if entity is selected
                   let world =
  
positive.code:                     else failwith ("Entity '" + scstring entity + " already exists and cannot be created."); world
                  else world
              let world = World.addEntity false entityState entity world
              
              // propagate properties
              let world =
                  if World.getEntityIsParent entity world then
  
negative.code:                 | None -> entityState
                  | Some names -> { entityState with Names = names }
  
              // make entity address
              let entityAddress = group.GroupAddress <-- rtoa<Entity> entityState.Names
  
              // make entity reference
              let entity = Entity entityAddress
  
              // apply publish bindings state
              match World.tryGetKeyedValueFast<UMap<Entity Address, int>> (EntityBindingCountsId, world) with
              | (true, entityBindingCounts) -> if UMap.containsKey entityAddress entityBindingCounts then entityState.PublishChangeBindings <- true
              | (false, _) -> ()
  
              // apply publish changes state
              match World.tryGetKeyedValueFast<UMap<Entity Address, int>> (EntityChangeCountsId, world) with
              | (true, entityChangeCounts) -> if UMap.containsKey entityAddress entityChangeCounts then entityState.PublishChangeEvents <- true
              | (false, _) -> ()
  
              // apply is parent state
              entityState.IsParent <- UMap.containsKey entity world.EntityHierarchy
  
              // add entity's state to world
              let world =
                  if World.getEntityExists entity world then
                      if World.getEntityDestroying entity world
  