/* This example demonstrates a bouncing ball with trails */


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

        public class Bounce3 extends Applet implements Runnable {

           private static final int XSIZE = 30;
           private static final int YSIZE = 30;
           private int x = 0;
           private int y = 0;
           private int dx = 2;
           private int dy = 2;   
           Thread myThread;

           Image offscreenImg;
           Graphics offscreenG;

           Color [] ballColors = {Color.red, Color.green, Color.pink,
                                  Color.yellow, Color.orange, Color.blue,
                                  Color.magenta, Color.cyan, Color.white};

           int colorIndex = 0;



           boolean justaRedBall = true;


           public void init() {



              offscreenImg = createImage(size().width, size().height);
              offscreenG = offscreenImg.getGraphics();



           }

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

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




          public boolean mouseDown(Event e, int x, int y) {
             justaRedBall = !justaRedBall;
             return true;
          }



   public void run()
   {
      int trailCntl = 0;

      while (true)
      {
        repaint();

        x += dx;
        y += dy;
        Dimension d = size();
        if (x < 0) { x = 0; dx = -dx; }
        if (x + XSIZE >= d.width) { x = d.width - XSIZE; dx = -dx; }
        if (y < 0) { y = 0; dy = -dy; }
        if (y + YSIZE >= d.height) { y = d.height - YSIZE; dy = -dy; }

        trailCntl = (trailCntl + 1) % 8;

        if (trailCntl == 0)
            colorIndex = (colorIndex + 1) % 9;
        

        try { Thread.sleep(15); } catch(InterruptedException e) {}

      }
   }



   public void paint(Graphics g) {


         if (justaRedBall) {


            offscreenG.setColor(Color.black);
            offscreenG.fillRect(0,0,size().width, size().height);
            offscreenG.setColor(Color.red);
            offscreenG.fillOval(x, y, XSIZE, YSIZE);
            g.drawImage(offscreenImg, 0, 0, this);

         }

         else {

               offscreenG.setColor(ballColors[colorIndex]);
               offscreenG.fillOval(x, y, XSIZE, YSIZE);
               g.drawImage(offscreenImg, 0, 0, this);
         } 
   }

   public void update(Graphics g) {
      paint(g);
   }



 }