Bagaimana untuk Mencipta Menu Jatuh Turun Berbilang Peringkat CSS Tulen?

.third-level-menu {
  position: absolute;
  top: 0;
  right: -150px;
  width: 150px;
  list-style: none;
  padding: 0;
  margin: 0;
  display: none;
}

.third-level-menu > li {
  height: 30px;
  background: #999999;
}
.third-level-menu > li:hover {
  background: #CCCCCC;
}

.second-level-menu {
  position: absolute;
  top: 30px;
  left: 0;
  width: 150px;
  list-style: none;
  padding: 0;
  margin: 0;
  display: none;
}

.second-level-menu > li {
  position: relative;
  height: 30px;
  background: #999999;
}
.second-level-menu > li:hover {
  background: #CCCCCC;
}

.top-level-menu {
  list-style: none;
  padding: 0;
  margin: 0;
}

.top-level-menu > li {
  position: relative;
  float: left;
  height: 30px;
  width: 150px;
  background: #999999;
}
.top-level-menu > li:hover {
  background: #CCCCCC;
}

.top-level-menu li:hover > ul {
  /* Display the next level's menu on hover */
  display: inline;
}

/* Menu Link Styles */

.top-level-menu a /* Apply to all links inside the multi-level menu */ {
  font: bold 14px Arial, Helvetica, sans-serif;
  color: #FFFFFF;
  text-decoration: none;
  padding: 0 0 0 10px;

  /* Make the link cover the entire list item-container */
  display: block;
  line-height: 30px;
}
.top-level-menu a:hover {
  color: #000000;
}

<ul class="top-level-menu">
    <li><a href="#">About</a></li>
    <li><a href="#">Services</a></li>
    <li>
        <a href="#">Offices</a>
        <ul class="second-level-menu">
            <li><a href="#">Chicago</a></li>
            <li><a href="#">Los Angeles</a></li>
            <li>
                <a href="#">New York</a>
                <ul class="third-level-menu">
                    <li><a href="#">Information</a></li>
                    <li><a href="#">Book a Meeting</a></li>
                    <li><a href="#">Testimonials</a></li>
                    <li><a href="#">Jobs</a></li>
                </ul>
            </li>
            <li><a href="#">Seattle</a></li>
        </ul>
    </li>
    <li><a href="#">Contact</a></li>
</ul>