CSS plynulé rozbalovací menu

<script type="text/javascript">
$(document).ready(function(){
$('#target').hide();
$('a#trigger').click(function (event) {
 event.preventDefault();
 $('#target').toggle(400);
});
});
  </script>
  
  <div class="prvek">
          <div class="odrazka">1.1</div><div class="prvek-text"><a href="" title="" id="trigger">ABC</a></div>
        </div>
        <menu id="target" style="display: none;">
          <div class="prvek">
            <div class="odrazka"></div><div class="prvek-text"><a href="" title="" >ABC</a></div>
          </div>
        </menu>