anchor.diff:          Map.filter (fun (k : CharacterIndex) _ -> not k.IsEnemy) this.CharacterCoordinates
       
       member this.PickupItems =
  -        Map.filter (fun _ v -> v <> None) this.PassableCoordinates
  +        Map.filter (fun _ (v : FieldSpace) -> v.ContainsPickup) this.PassableCoordinates
   
       member this.EnemyCount =
           this.EnemyCoordinates.Count
  
positive.code:         Gameplay.updateChessboardBy Chessboard.truncatePlayerPath () () gameplay
      
      static member addHealth coordinates gameplay =
          Gameplay.updateChessboardBy Chessboard.updateCoordinatesValue (Some Health) coordinates gameplay
  
      static member removeHealth coordinates gameplay =
          Gameplay.updateChessboardBy Chessboard.updateCoordinatesValue None coordinates gameplay
      
      static member clearPickups gameplay =
          Gameplay.updateChessboardBy Chessboard.clearPickups () () gameplay
  
negative.code:         Map.exists (fun k _ -> k = index) chessboard.CharacterCoordinates
      
      static member pickupAtCoordinates coordinates chessboard =
          chessboard.PassableCoordinates.[coordinates].ContainsPickup
      
      static member updateCoordinatesValue updater coordinates chessboard =
          let passableCoordinates = Map.add coordinates (updater chessboard.PassableCoordinates.[coordinates]) chessboard.PassableCoordinates
          Chessboard.updatePassableCoordinates (constant passableCoordinates) chessboard
      
      static member clearPickups _ _ chessboard =
          let passableCoordinates = Map.map (fun _ v -> FieldSpace.removePickup v) chessboard.PassableCoordinates
          Chessboard.updatePassableCoordinates (constant passableCoordinates) chessboard
      
      // used for both adding and relocating
  