private void initGUI() {
		boxs = new BoxLabel[SDK_SIZE][SDK_SIZE];
		for (int i = 0; i < SDK_SIZE; i++) {
			for (int j = 0; j < SDK_SIZE; j++) {
				BoxLabel box = new BoxLabel(i, j);
				// ve cac duong ngang
				if (i == 3 || i == 6)
					box.setBorder(BorderFactory.createMatteBorder(
							1, 0, 0, 0, Color.GRAY));
				// ve cac duong doc
				if (j == 3 || j == 6) {
					box.setBorder(BorderFactory.createMatteBorder(
							0, 1, 0, 0, Color.GRAY));
					if (i == 3 || i == 6) {
						// fix lai cac diem giao nhau
						box.setBorder(BorderFactory.createMatteBorder(
								1, 1, 0, 0, Color.GRAY));
					}
				}
				box.addMouseListener(boxClickEvent);
				add(box);
				boxs[i][j] = box;
			}
		}
	}