The Code for the FloatingSprite

/**
 * An encapsulation of a Sprite that "floats" from the top of the
 * Stage to the bottom
 *
 * @author  Prof. David Bernstein, James Madison University
 * @see     "The Design and Implementation of Multimedia Software (c) 2011"
 * @version 1.0
 *
 * @augments AbstractSprite
 */

FloatingSprite.prototype = new AbstractSprite();
FloatingSprite.prototype.constructor = FloatingSprite;


/**
 * Explicit Value Constructor
 *
 * @param {Content}  The static content (either described or sampled)
 * @param {float}    The width of the Stage
 * @param {float}    The height of the Stage
 */
function FloatingSprite(content, width, height)
{
   this.content = content;
   this.maxX    = width;
   this.maxY    = height;       
   
   this.x = Math.random()*this.maxX;       
   this.y = 0.0;       
   this.setLocation(this.x, this.y);       
   
   this.setVisible(true);
}



/**
 * Get the (current) content associated with this Sprite
 *
 * @returns {Content} The static visual content
 */
FloatingSprite.prototype.getContent = function()
{
   return this.content;
}

/**
 * Handle a tick from the metronome
 * (required by MetronomeListener)
 *
 * @param {int} time   The time
 */
FloatingSprite.prototype.handleTick = function(time)
{
   var n = Math.random();

   if      (n < 0.80)   this.y += 2.0;
   else if (n > 0.90)   this.y -= 1.0;       
   
   n = Math.random();
   if      (n < 0.20) this.x -= 1.0;
   else if (n > 0.80) this.x += 1.0;
   
   // Check if at the bottom
   if (this.y > this.maxY)
   {
      this.y  = 0.0;
      this.x = Math.random()*this.maxX;       
   }
   
   this.setLocation(this.x, this.y);       
}