anchor.diff:        savedMarkdown.isNotEmpty &&
         savedMarkdown != introText) {
       markdownInput.value = savedMarkdown;
  +    markdownInput.focus();
       _renderMarkdown();
     } else {
       _typeItOut(introText, 82);
  
positive.code:     markdownInput.focus();
      _renderMarkdown();
      pos++;
      new Timer(typing, addCharacter);
    }
  
    new Timer(typing, addCharacter);
  }
  
  class NullTreeSanitizer implements NodeTreeSanitizer {
  
negative.code: }
  
  void _typeItOut(String msg, int pos) {
    Timer timer;
    markdownInput.onKeyUp.listen((_) {
      timer?.cancel();
    });
    addCharacter() {
      if (pos > msg.length) {
        return;
  