import java.awt.*;

public class BouncingBall {

   private Color color;  
   private int radius;   
   private double centerX, centerY;      
   private double velocityX, velocityY;  

   public BouncingBall(Color color, int centerX, int centerY, int radius) {
        
      this.color = color;
      this.centerX = centerX;
      this.centerY = centerY;
      this.radius = radius;
      do {
         velocityX = (int)(20*Math.random() - 10);
         velocityY = (int)(20*Math.random() - 10);
      } while (Math.abs(velocityY) <= 2 && Math.abs(velocityX) <= 2);
   }
   

   public void doFrame(Graphics g, int width, int height) {
       
      g.setColor(color);
      g.fillOval((int)centerX - radius, (int)centerY - radius, 4*radius, 4*radius);
      centerX += velocityX;
      centerY += velocityY;
      if (centerX - radius < 0)
         velocityX = Math.abs(velocityX);
      if (centerX + radius >= width)
         velocityX = -Math.abs(velocityX);
      if (centerY - radius < 0)
         velocityY = Math.abs(velocityY);
      if (centerY + radius >= height)
         velocityY = -Math.abs(velocityY);
   }
   
 
   public void setPosition(int x, int y) {
          
      this.centerX = x;
      this.centerY = y;
   }
   
    public void headTowards(int x, int y) {
        
      if (Math.abs(x - centerX) < 1.0E-10 && Math.abs(y - centerY) < 1.0E-10)
         return;
      double v = Math.sqrt(velocityX*velocityX + velocityY*velocityY);
      double d = Math.sqrt((x-centerX)*(x-centerX) + (y-centerY)*(y-centerY));
      velocityX = (x-centerX)*v/d;
      velocityY = (y-centerY)*v/d;
   }


}