package {
          import flash.display.Sprite;
          
          public class @ax-animation-ch19-Ball extends Sprite {
                  public var radius:Number;
                  private var color:uint;
                  public var vx:Number = 0;
                  public var vy:Number = 0;
                  public var mass:Number = 1;
                  
                  public function @ax-animation-ch19-Ball(radius:Number=40, color:uint=0xff0000) {
                          this.radius = radius;
                          this.color = color;
                          init();
                  }
                  public function init():void {
                          graphics.beginFill(color);
                          graphics.drawCircle(0, 0, radius);
                          graphics.endFill();
                  }
          }
  }