public void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;

    // TODO: wrong for dist=51, wrong for dist=52
    buffer = ring.buffer(51);

    g2.setColor(Color.CYAN);
    buffer.fill(g2);
    g2.setColor(Color.BLUE);
    buffer.draw(g2);

    g2.setColor(Color.BLACK);
    ring.draw(g2);
  }