void insertBars(Ladder ladder, Coordinate leftPoint, Coordinate rightPoint) {
		// int에서 1을 빼는 로직을 for문의 조건으로 넣었다. 개선의 여지가 있을까...
		for (leftPoint.getX(); leftPoint.getX() < columns - 1; leftPoint.incrementX()) {
			for (leftPoint.getY(); leftPoint.getY() < columnLength; leftPoint.incrementY()) {
				System.out.println("try left point: " + leftPoint.getX() + ", " + leftPoint.getY());
				if (getBarInsertionPermission() && isEmptyPoint(ladder, leftPoint.getX(), leftPoint.getY())) {
					System.out.println("got left permission");
					rightPoint = getRightPoint(ladder, leftPoint);
					connectDots(ladder, leftPoint, rightPoint);
				}
			}
			leftPoint.resetY();
		}
	}