anchor.diff:  
       let handleFormCreate atMouse (form : NuEditForm) (worldChangers : WorldChangers) refWorld (_ : EventArgs) =
           ignore <| worldChangers.Add (fun world ->
  -            try let entityDispatcherName = form.createEntityComboBox.Text
  -                let (entity, world) = World.createEntity entityDispatcherName None EditorGroup world
  -                let world = pushPastWorld world world
  +            try let world = pushPastWorld world world
  +                let (entity, world) = World.createEntity form.createEntityComboBox.Text None EditorGroup world
                   let (positionSnap, rotationSnap) = getSnaps form
                   let mousePosition = World.getMousePositionF world
                   let entityPosition =
  
positive.code: 
      let handleFormDelete (form : NuEditForm) (worldChangers : WorldChangers) (_ : EventArgs) =
          ignore <| worldChangers.Add (fun world ->
              let selectedObject = form.propertyGrid.SelectedObject
              let world = pushPastWorld world world
              match selectedObject with
              | :? EntityTypeDescriptorSource as entityTds ->
                  let world = World.destroyEntity entityTds.DescribedEntity world
                  form.propertyGrid.SelectedObject <- null
  
negative.code:         
      let handleFormCopy (form : NuEditForm) (worldChangers : WorldChangers) (_ : EventArgs) =
          ignore <| worldChangers.Add (fun world ->
              match form.propertyGrid.SelectedObject with
              | null -> world
              | :? EntityTypeDescriptorSource as entityTds ->
                  let entity = World.getEntity entityTds.Address world
  