CSS如何将固定菜单添加到视差网站布局

<nav id="fixed-menu">
  <ul>
    <li><a href="#section1">Section 1</a></li>
    <li><a href="#section2">Section 2</a></li>
    <li><a href="#section3">Section 3</a></li>
  </ul>
</nav>

<section id="section1">
  <!-- Content of section 1 -->
</section>

<section id="section2">
  <!-- Content of section 2 -->
</section>

<section id="section3">
  <!-- Content of section 3 -->
</section>

#fixed-menu {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background-color: #fff;
  z-index: 999;
  transition: all 0.3s ease;
}

#fixed-menu ul {
  list-style: none;
  display: flex;
  justify-content: space-around;
}

#fixed-menu li {
  margin: 0 10px;
}

#fixed-menu a {
  text-decoration: none;
  color: #000;
  font-weight: bold;
}

section {
  height: 100vh;
  margin-top: 50px; /* Add margin to make content visible below the fixed menu */
  background-color: #f5f5f5;
}