public final class Panel extends JPanel implements MouseListener {

		private int boardTopLeftX;
		private int boardTopLeftY;

		private Boolean userClicked;
		private int userClickCol;

		public Panel() {
			super();
			this.boardTopLeftX = cellSize;
			this.boardTopLeftY = 2*cellSize;
			this.userClicked = false;
		}

		@Override
		public void paintComponent(Graphics g) {
			g.setColor(COLOR);

			int verticalLineLength = cellSize * ROW_CONSTANT;
			int horizontalLineLength = cellSize * COL_CONSTANT;

			//GUI draw vertical lines
			for (int colNum = 0; colNum <= COL_CONSTANT; colNum++) {
				int xCoord = boardTopLeftX + colNum * cellSize;
				g.drawLine(xCoord, boardTopLeftY, xCoord, boardTopLeftY + verticalLineLength);
			}

			//GUI draw horizontal lines
			for (int rowNum = 0; rowNum <= ROW_CONSTANT; rowNum++) {
				int yCoord = boardTopLeftY + rowNum * cellSize;
				g.drawLine(boardTopLeftX, yCoord, boardTopLeftX + horizontalLineLength, yCoord);
      }
		}

		@Override
		public void mouseClicked(MouseEvent e) {
			synchronized (userClicked) {
				userClickCol = getColOfClick(e.getX(), e.getY());
				userClicked.notifyAll();
			}
		}

		/**
		 * Returns column where user clicked above board
		 */
		private int getColOfClick(int x, int y) {
			int pieceDiameter = cellSize - BORDER*2;

			for (int col = 0; col < COL_CONSTANT; col++) {
				int distBetweenClickAndCenter =
						euclidDistance(x, y,
												   boardTopLeftX + (int) ((col + 0.5) * cellSize),
												   boardTopLeftY - (int) (0.5 * cellSize));
				if (distBetweenClickAndCenter < pieceDiameter / 2) {
					return col;
				}
			}
			return -1;
		}

		public int getUserClickCol() {
			return userClickCol;
		}

		@Override
		public void mouseEntered(MouseEvent e) {}

		@Override
		public void mouseExited(MouseEvent e) {}

		@Override
		public void mousePressed(MouseEvent e) {}

		@Override
		public void mouseReleased(MouseEvent e) {}
	}
}