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