public class @ax-animation-ch18-Ball3D extends Sprite {
                  public var radius:Number;
                  private var color:uint;
                  public var xpos:Number = 0;
                  public var ypos:Number = 0;
                  public var zpos:Number = 0;
                  public var vx:Number = 0;
                  public var vy:Number = 0;
                  public var vz:Number = 0;
                  public var mass:Number = 1;