import java.applet.*;
import java.awt.*;

abstract class Animation {
    protected Applet app;

    protected void init(Applet app) {
	this.app = app;
    }

    public abstract void advance();

    public abstract void paintFrame(Graphics g);
}

class StarAnimation extends Animation {
    private Color color = new Color(0,0,0);
    private static int i = 0, r = 0, g = 0, b = 0;

    public void advance() {
	switch (i++) {
	    case 5:
		color = Color.darkGray;
		break;
	    case 6:
		color = Color.lightGray;
		break;
	    case 7:
		color = Color.white;
		break;
	    case 8:
		color = Color.lightGray;
		break;
	    case 9:
		color = Color.darkGray;
		break;
	    case 50:
		color = Color.black;
		i = 0;
		break;
	    default:
		color = Color.black;
		break;
	}
    }
	

    public void paintFrame(Graphics g) {
	Rectangle bounds = app.bounds();
        g.setColor(Color.black);
	g.fillRect(0,0,bounds.width,bounds.height);
        g.setColor(color);
	g.fillOval(0,0,bounds.width,bounds.height);
    }
}

public class Pulsar extends Applet implements Runnable {
    Thread animator;
    Animation animation;
    private int timing;
    private StringBuffer timingStringBuf;

    public void init() {
	animator = new Thread(this);
	animation = new StarAnimation();
	animation.init(this);
	timingStringBuf = getParameter("timing");
	timing = (int) timingStringBuf.toString()
    }

    public void start() {
	if (animator.isAlive()) { animator.resume(); }
	else { animator.start(); }
    }

    public void stop() {
	animator.suspend();
    }

    public void destroy() {
	animator.stop();
    }

    public void run() {
      try {
	while (true) {
	    repaint();
	    Thread.sleep(100);
	    animation.advance();
	}
      }
      catch (Exception e) {
	e.printStackTrace();
	return;
      }
    }

    public void paint(Graphics g) {
	animation.paintFrame(g);
    }
}