anchor.diff:      s.pos.z = attr('data-z');
       s.rot.x = attr('data-rotate-x');
       s.rot.y = attr('data-rotate-y');
  -    s.rot.z = attr('data-rotate-z');
  +    // Treat data-rotate as data-rotate-z:
  +    // Allows using only data-rotate for pure 2D rotation
  +    s.rot.z = attr('data-rotate-z', attr('data-rotate'));
       return s;
     }
   
  
positive.code:   ElementList mSteps;
    // Index of the currently active step
    int mCurrentStep;
    
    Config mCfg;
  
    Impress()
  
negative.code:     // force going to active step again, to trigger rescaling
      pres.goto(pres.mCurrentStep);
    }, 250));
  
  }
  
  /**
  