如何让一个元素平滑的展开自己？

Question

我需要最深的

li>span

文本来平滑地扩展自己，因为我在

div

上徘徊与

li

类。

ul {
  list-style-type: none;
}

.kinds {
  width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.drop_vert_menu {
  text-align: center;
  width: 600px;
  margin: 0;
  padding: 0;
}

.drop_vert_menu li ul {
  list-style-type: none;
  width: 600px;
  padding: 0;
  background-color: #666;
  position: relative;
  display: none;
}

.drop_vert_menu>li {
  margin-left: auto;
  margin-right: auto;
  position: relative;
  padding: 10px 0px;
}

.drop_vert_menu li:hover ul {
  display: block;
}

.drop_vert_menu li ul li {
  text-align: center;
  padding: 8px 0px;
}

<div class="kinds">
  <ul class="drop_vert_menu">
    <li>
      <div class="li"><span>text that expands</span>
        <ul>
          <li><span>text that should be expanded</span></li>
        </ul>
      </div>
    </li>
  </ul>
</div>