import java.awt.*;


 public class BouncingBall extends AnimationApplet{

   protected Color color = Color.magenta;
   // radius of the ball
   protected int radius = 20;
   protected int radius2 = 20;
   protected int x1, y1;
   protected int x2, y2;
   protected int dist;
   // how much the location changes at every redraw
   protected int dx1 = -2, dy1 = -4;
   protected int dx2 = -2, dy2 = -4;
   // off screen image
   protected Image image1;
   protected Image image2;
   // off screen graphics
   protected Graphics offscreen;
   // dimensions of the applet region
   protected Dimension d;

   public void init() {
     String att = getParameter("delay");
     if (att != null) {
       setDelay(Integer.parseInt(att));
     }
     else{
       setDelay(100); // default
     }

     d = getSize();

     // set the starting point of the ball
     x1 = d.width * 2 / 3;
     y1 = d.height - radius;
     x2 = d.width * 2 / 4;
     y2 = d.height - radius;
   }


   public void update(Graphics g) {
     // create the off-screen image buffer
     // if it is invoked the first time
     if (image1 == null) {
       image1 = createImage(d.width, d.height);
       offscreen = image1.getGraphics();
     }

    // draw the background
    offscreen.setColor(Color.cyan);
    offscreen.fillRect(0,0,d.width,d.height);

    // adjust the position of the ball
    // reverse the direction if it touches
    // any of the four sides
    if (x1 < radius || x1 > d.width - radius) {
	 dx1  =  -dx1;
    }
    if (y1 < radius || y1 > d.height - radius) {
      dy1  =  -dy1;
    }
    x1 += dx1;
    y1 += dy1;

    if (x2 < radius || x2 > d.width - radius) {
	    dx2  =  -dx2;
	}
	if (y2 < radius || y2 > d.height - radius) {
	    dy2  =  -dy2;
	 }

	 x2 += dx2;
     y2 += dy2;

     double XResult = x2 - x1;
     double YResult = y2 - y1;

     double Dist = Math.pow(XResult, 2) + Math.pow(YResult, 2);
     double DResult = Math.sqrt(Dist);

     if ((DResult < (2 * radius)) || (DResult == (2 * radius ))) {
		 DResult = DResult + 40;
		 dx2 = -dx2 + 1;		// Reverse the direction if it collides
		 dy2 = -dy2;
		 dx1 = -dx1 + 1;
		 dy1 = -dy1 + 1;

	 }

    // draw the ball
    offscreen.setColor(color);
    offscreen.fillOval(x1 - radius, y1 - radius,
                            radius * 2, radius * 2);
    offscreen.fillOval(x2 - radius, y2 - radius,
                            radius * 2, radius * 2);

     // copy the off-screen image to the screen
     g.drawImage(image1, 0, 0, this);

   }

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