import java.awt.*;

public class Bouncer extends SimpleAnimationApplet {

	double redCenterX, redCenterY;
	double blueCenterX, blueCenterY;
	double greenCenterX, greenCenterY;
	
	double redVelocityX, redVelocityY;
	double blueVelocityX, blueVelocityY;
	double greenVelocityX, greenVelocityY;
	
	boolean starting = true; 
	
	protected void drawFrame(Graphics g, int width, int height) {
	
	g.setColor(Color.yellow);  
        g.fillRect(0,0,width,height);
        
        if (starting) {
           initializeRedCircle(width,height);
           initializeBlueCircle(width,height); 
           initializeGreenCircle(width,height);   
                                               
           starting = false;  
                              
        }
        
        g.setColor(Color.red);
        g.fillOval((int)redCenterX - 25, (int)redCenterY - 25, 50, 50);  
             
        g.setColor(Color.blue);
        g.fillOval((int)blueCenterX - 25, (int)blueCenterY - 25, 50, 50);  
        
        g.setColor(Color.green);
        g.fillOval((int)greenCenterX - 25, (int)greenCenterY - 25, 50, 50);  
        
        updateRedCircle(width,height);
        updateBlueCircle(width,height);
        updateGreenCircle(width,height);
        
        g.setColor(Color.black);  
        g.drawRect(0,0,width-1,height-1);

     } 
     
  void initializeRedCircle(int width, int height) {
     
      redCenterX = width / 2;
      redCenterY = height / 2;

        do {
           redVelocityX = 12 * (Math.random() - 0.5);
        } while (Math.abs(redVelocityX) < 3);

        do {
           redVelocityY = 12 * (Math.random() - 0.5);
        } while (Math.abs(redVelocityY) < 3);

   }
   
  void updateRedCircle(int width, int height) {
          

       redCenterX += redVelocityX;
       redCenterY += redVelocityY;

       if (redCenterX - 25  <=  0)  
          redVelocityX = Math.abs(redVelocityX); 

       if (redCenterX + 25  >=  width) 
          redVelocityX = - Math.abs(redVelocityX);

       if (redCenterY - 25  <=  0)  
          redVelocityY = Math.abs(redVelocityY);  

       if (redCenterY + 25  >=  width) 
          redVelocityY = - Math.abs(redVelocityY); 

}  
  void initializeBlueCircle(int width, int height) {
     
      blueCenterX = width /9 ;
      blueCenterY = height /9 ;

        do {
           blueVelocityX = 10 * (Math.random() - 0.5);
        } while (Math.abs(blueVelocityX) < 3);

        do {
           blueVelocityY = 10 * (Math.random() - 0.5);
        } while (Math.abs(blueVelocityY) < 3);

   } 
   
  void updateBlueCircle(int width, int height) {
          

       blueCenterX += blueVelocityX;
       blueCenterY += blueVelocityY;

       if (blueCenterX - 25  <=  0)  
          blueVelocityX = Math.abs(blueVelocityX);  

       if (blueCenterX + 35  >=  width) 
          blueVelocityX = - Math.abs(blueVelocityX); 

       if (blueCenterY - 25  <=  0)  
          blueVelocityY = Math.abs(blueVelocityY);  

       if (blueCenterY + 18  >=  width) 
          blueVelocityY = - Math.abs(blueVelocityY); 

}  
  void initializeGreenCircle(int width, int height) {
     
      greenCenterX = width / 6;
      greenCenterY = height / 6;

        do {
           greenVelocityX = 16 * (Math.random() - 0.5);
        } while (Math.abs(greenVelocityX) < 3);

        do {
           greenVelocityY = 16 * (Math.random() - 0.5);
        } while (Math.abs(greenVelocityY) < 3);

   } 
   
  void updateGreenCircle(int width, int height) {
          

       greenCenterX += greenVelocityX;
       greenCenterY += greenVelocityY;

       if (greenCenterX - 25  <=  0)  
          greenVelocityX = Math.abs(greenVelocityX); 

       if (greenCenterX + 25  >=  width) 
          greenVelocityX = - Math.abs(greenVelocityX); 

       if (greenCenterY - 25  <=  0)  
          greenVelocityY = Math.abs(greenVelocityY);  
       if (greenCenterY + 25  >=  width) 
          greenVelocityY = - Math.abs(greenVelocityY); 

  }  
}