         guard gameBoard != nil else { return }
         
         let
-        borderRect    = calculatePlatformBorderRect(),
+        borderRect    = platformBorderRect,
         platformRect  = platformRectFromBorderRect(borderRect),
         gridLineRects = gridLineRectsFromPlatformRect(platformRect)
         

        
        let
        tapLocation    = touch.locationInView(self),
        borderRect     = calculatePlatformBorderRect(),
        platformRect   = platformRectFromBorderRect(borderRect),
        emptyPositions = gameBoard.emptyPositions,
        emptyCellRects = calculateCellRectsWithPositions(emptyPositions, inRect: platformRect),
        emptyPositionsAndRects = Array(zip(emptyPositions, emptyCellRects))
        
        let tappedPositions = emptyPositionsAndRects.flatMap { (position, rect) in

            let marksInRow = gameBoard.marksInRow(row)
            for column in 0..<gameBoard.dimension {
                if let mark = marksInRow[column] {
                    let cellRect = cellRectAtRow(row, column: column, inRect: rect)
                    drawMark(mark, inRect: cellRect)
                }
            }
