如何使我的响应式导航栏粘性只有HTML和CSS？

<nav>
  <ul>
    <li><a href="#">首页</a></li>
    <li><a href="#">关于</a></li>
    <li><a href="#">服务</a></li>
    <li><a href="#">联系我们</a></li>
  </ul>
</nav>

nav {
  position: fixed;
  top: 0;
  width: 100%;
  background-color: #f8f8f8;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
}

li {
  float: left;
}

li a {
  display: block;
  padding: 10px 20px;
  text-decoration: none;
  color: #333;
}

li a:hover {
  background-color: #ddd;
}

@media screen and (max-width: 768px) {
  nav {
    position: static;
  }
  
  li {
    float: none;
  }
  
  li a {
    display: inline-block;
  }
}