// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 22-1: Inheritance
  
  class Circle extends Shape {
    
    // Inherits all instance variables from parent + adding one
    color c;
    
    Circle(float x_, float y_, float r_, color c_) {
      super(x_,y_,r_); // Call the parent constructor
      c = c_;          // Also deal with this new instance variable
    }
    
    // Call the parent jiggle, but do some more stuff too
    void jiggle() {
      super.jiggle();
      // The Circle jiggles its size as well as its x,y location.
      r += random(-1,1); 
      r = constrain(r,0,100);
    }
    
    // The changeColor() function is unique to the Circle class.
    void changeColor() { 
      c = color(random(255));
    }
    
    void display() {
      ellipseMode(CENTER);
      fill(c);
      stroke(0);
      ellipse(x,y,r,r);
    }
  }