code: public void moveAndFadeIn (Path path, long pathDuration, float fadePortion)
      {
          move(path);
  
          setAlpha(0.0f);
  
          _fadeInDuration = (long)(pathDuration * fadePortion);
      }
docs: Puts this sprite on the specified path and fades it in over the specified duration.
  
  @param path the path to move along
  @param fadePortion the portion of time to spend fading in, from 0.0f (no time) to 1.0f (the
  entire time)