anchor.diff:          match node.Children with
           | Left nodes ->
               for node in nodes do
  -                if intersectingBounds oldBounds node || intersectingBounds newBounds node then
  +                if isIntersectingBounds oldBounds node || isIntersectingBounds newBounds node then
                       updateElement oldBounds newBounds element node
           | Right elements ->
  -            if intersectingBounds oldBounds node then
  -                if not (intersectingBounds newBounds node) then elements.Remove element |> ignore
  -            elif intersectingBounds newBounds node then
  +            if isIntersectingBounds oldBounds node then
  +                if not (isIntersectingBounds newBounds node) then elements.Remove element |> ignore
  +            elif isIntersectingBounds newBounds node then
                   elements.Add element |> ignore
   
       let rec internal getElementsAtPoint point node (set : 'e HashSet) =
  
positive.code:         if omnipresent then 
              tree.OmnipresentElements.Remove element |> ignore
          else
              if not (SpatialNode.intersectingBounds bounds tree.Node) then
                  Log.info "Element is outside spatial tree's containment area or is not present for removal."
                  tree.OmnipresentElements.Remove element |> ignore
              else SpatialNode.removeElement bounds element tree.Node
  
      let updateElement oldBounds newBounds element tree =
          let oldInBounds = SpatialNode.intersectingBounds oldBounds tree.Node
          let newInBounds = SpatialNode.intersectingBounds newBounds tree.Node
          if oldInBounds && not newInBounds then
              // going out of bounds
              Log.info "Element is outside spatial tree's containment area."
  
negative.code:     let internal atPoint point node =
          Math.isPointInBounds point node.Bounds
  
      let internal isIntersectingBounds bounds node =
          Math.isBoundsIntersectingBounds bounds node.Bounds
  
      let rec internal addElement bounds element node =
          if isIntersectingBounds bounds node then
              match node.Children with
              | Left nodes -> for node in nodes do addElement bounds element node
              | Right elements -> elements.Add element |> ignore
  
      let rec internal removeElement bounds element node =
          if isIntersectingBounds bounds node then
              match node.Children with
              | Left nodes -> for node in nodes do removeElement bounds element node
              | Right elements -> elements.Remove element |> ignore
  