/**
 *    Program:  Mix2
 *    @author:  Paul Garrett, garrett@math.umn.edu
 *    @version: Tue Dec 28 16:58:27 CST 1999
 *
 *    Purpose:  
 *
 */

import java.awt.*;

public class Mix2 extends java.applet.Applet implements Runnable {

	 int a = 3;
	 int b = 1;
	 int c = 1;
	 int d = 2;

	 int aa = 1;
	 int bb = 0;
	 int cc = 0;
	 int dd = 1;

	 Thread th;
	 int counter = 0;

	 public void start() {
		  if (th == null) {
				th = new Thread(this);
				th.start();
		  }
	 }

	 public void stop() {
		  if (th != null) {
				th.stop();
				th = null;
		  }
	 }

	 public void pause(int time) {
		  try {
				th.sleep( time );
		  }
		  catch (Exception e) {
				// do nothing
		  }
		  //		  System.out.println("Waking up");
	 }

	 public void run() {
		  while (true) {
				pause( 1000 );
				counter++;
				int atmp = aa;
				int btmp = bb;
				int ctmp = cc;
				int dtmp = dd;
				aa = a*atmp + b*ctmp;
				bb = a*btmp + b*dtmp;
				cc = c*atmp + d*ctmp;
				dd = c*btmp + d*dtmp;
				repaint();
				//				System.out.println("iterating");
		  }
	 }

  	 public void paint(Graphics g) {
		  int[] xy = new int[2];
		  int[] zw = new int[2];
		  g.setColor(Color.red);
		  for (int i=0; i<100; i++) {       // upper left 1/5 x 1/5
				for (int j=0; j<100; j++) {
					 xy[0] = i;
					 xy[1] = j;
					 zw = f(xy);
					 g.fillRect(zw[0],zw[1],1,1);
				}
		  }
		  g.setColor(Color.blue);
		  for (int i=100; i<200; i++) {
				for (int j=0; j<100; j++) {
					 xy[0] = i;
					 xy[1] = j;
					 zw = f(xy);
					 g.fillRect(zw[0],zw[1],1,1);
				}
		  }
		  g.setColor(Color.green);
		  for (int i=0; i<100; i++) {
				for (int j=100; j<200; j++) {
					 xy[0] = i;
					 xy[1] = j;
					 zw = f(xy);
					 g.fillRect(zw[0],zw[1],1,1);
				}
		  }
		  g.setColor(Color.yellow);
		  for (int i=100; i<200; i++) {
				for (int j=100; j<200; j++) {
					 xy[0] = i;
					 xy[1] = j;
					 zw = f(xy);
					 g.fillRect(zw[0],zw[1],1,1);
				}
		  }
		  //		  g.setColor(Color.black);
		  //		  g.drawRect(0,0,500,500);
  	 }

	 int[] f( int[] xy ) {
		  // 499 is prime...
		  int[] out = new int[2];
		  out[0] = (aa*xy[0]+bb*xy[1]) % 499;
		  out[1] = (cc*xy[0]+dd*xy[1]) % 499;
		  return out;
	 }

}
    
/**************************************************
 *
 *   The End
 *
 ***************************************************/