anchor.diff:              Chessboard.updateCharacterCoordinates (constant characterCoordinates) chessboard
           else failwith "character placement failed; coordinates unavailable"
   
  +    static member addCharacter index coordinates (chessboard : Chessboard) =
  +        Chessboard.placeCharacter index coordinates chessboard
  +
  +    static member relocateCharacter index coordinates (chessboard : Chessboard) =
  +        Chessboard.placeCharacter index coordinates chessboard
  +    
       static member removeCharacter index _ chessboard =
           let characterCoordinates = Map.remove index chessboard.CharacterCoordinates
           Chessboard.updateCharacterCoordinates (constant characterCoordinates) chessboard
  
positive.code:         FieldSpace.updatePickupItemOpt (constant None) fieldSpace
      
      static member empty =
          { PickupItemOpt = None }
  
  type [<ReferenceEquality; NoComparison>] Chessboard =
      { PassableCoordinates : Map<Vector2i, FieldSpace>
  
negative.code:     static member pickupAtCoordinates coordinates chessboard =
          chessboard.PassableCoordinates.[coordinates].ContainsPickup
      
      static member updateCoordinatesValueInternal updater coordinates (passableCoordinates : Map<Vector2i, FieldSpace>) =
          Map.add coordinates (updater passableCoordinates.[coordinates]) passableCoordinates
  
      static member updateCoordinatesValue updater coordinates chessboard =
          Chessboard.updatePassableCoordinates (Chessboard.updateCoordinatesValueInternal updater coordinates) chessboard
      
      static member addHealth _ coordinates chessboard =
          Chessboard.updateCoordinatesValue FieldSpace.addHealth coordinates chessboard
  
      static member removePickup _ coordinates chessboard =
          Chessboard.updateCoordinatesValue FieldSpace.removePickup coordinates chessboard
      
      static member clearPickups _ _ chessboard =
          let passableCoordinates = Map.map (fun _ v -> FieldSpace.removePickup v) chessboard.PassableCoordinates
  