// The name of our class
class Ball
{

  // our Class variables.  
  int wWidth;
  int wHeight;
  int bSize;
  
  int x, y;
  int xDirection, yDirection;
  
  // Constructor.  This gets called when we create a "new Ball"
  Ball(int windowWidth, int windowHeight, int ballSize)
  {
    wWidth = windowWidth;
    wHeight = windowHeight;
    bSize = ballSize;
    x = 1;
    y = 1;
    xDirection = 1;
    yDirection = 1;
  }
  
  Ball(int windowWidth, int windowHeight, int ballSize, int xPosition, int yPosition)
  {
    this(windowWidth, windowHeight, ballSize);
    x = xPosition;
    y = yPosition;
  }
  
  // Our method to determine current position of the ball.
  void compute()
  {
    if (x < wWidth && x > 0)
    {
      // Move along x axis
      x += xDirection;
    }
    else
    {
      // Change direction, from positive to negative and vice versa
      xDirection = xDirection * -1;
      x += xDirection;
    }
    
    if (y < wHeight && y > 0)
    {
      y += yDirection;    
    }
    else
    {
      yDirection = yDirection * -1;
      y += yDirection;
    }
  }
  
  // This actually displays our ball, it gets called in the main draw function
  void display()
  {
    compute();  // first we run the computation
    ellipseMode(CENTER);
    ellipse(x,y,bSize,bSize);   
  }

}