code: function ( progress ) {
              if ( $B.isNumber(progress) ) {
                  if ( !this._disabed ) {
                      var clockwise = ( this._progress < progress ),
                          grow = this._getGrow( this._progress, progress, clockwise ),
                          center = this._centerPoint,
                          degree = this._progressToDeg( progress ),
                          point = this._getPoint( degree, center );
      
                      this._dispatch( 'rotation', undefined, degree, point, point, center, grow );
                  }
                  return this;
              } else {
                  return this._progress;
              }
          }
docs: 회전 각도설정 및 반환
  @param	{Number}	progress
  @return	{RotationEvent, Number}