// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 10-2: Bouncing ball class
  
  class Ball {
  
    float r;   // radius
    float x,y; // location
    float xspeed,yspeed; // speed
    
    // Constructor
    Ball(float tempR) {
      r = tempR;
      x = random(width);
      y = random(height);
      xspeed = random( - 5,5);
      yspeed = random( - 5,5);
    }
    
    void move() {
      x += xspeed; // Increment x
      y += yspeed; // Increment y
      
      // Check horizontal edges
      if (x > width || x < 0) {
        xspeed *= - 1;
      }
      //Check vertical edges
      if (y > height || y < 0) {
        yspeed *= - 1;
      }
    }
    
    // Draw the ball
    void display() {
      stroke(0);
      fill(0,50);
      ellipse(x,y,r*2,r*2);
    }
  }