private List<TSquare> getEmptySq(int xLeft, int xRange, int lineY) {
		List<TSquare> sqOccupied = getOccupiedSq(xLeft, xRange, lineY);
		List<TSquare> sqEmpty = new ArrayList<TSquare>();
		if (!sqOccupied.isEmpty()) {	//only consider occupied situation, otherwise, it's the edge
			int xRight = xLeft + xRange;
			for (int x = xLeft; x < xRight; x++) {
				boolean isEmpty = true;
				for (TSquare sq: sqOccupied) {
					int sqX = (int)sq.getX();
					if (sqX == x) {
						isEmpty = false;
					}
				}
				if (isEmpty) {
					TSquare nsq = new TSquare();
					nsq.setSqCoordinate(x, lineY);
					sqEmpty.add(nsq);
				}
			}
			
		}
		return sqEmpty;
	}