如何用纯CSS切换侧边栏菜单？

<div class="sidebar">
  <input type="checkbox" id="toggle">
  <label for="toggle" class="toggle-btn"></label>
  <ul class="menu">
    <li><a href="#">菜单项1</a></li>
    <li><a href="#">菜单项2</a></li>
    <li><a href="#">菜单项3</a></li>
  </ul>
</div>

.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 300px;
  height: 100%;
  background-color: #333;
  transition: width 0.3s;
}

.sidebar .toggle-btn {
  position: absolute;
  top: 10px;
  left: 10px;
  width: 20px;
  height: 20px;
  background-color: #fff;
  cursor: pointer;
}

.sidebar .toggle-btn::before,
.sidebar .toggle-btn::after {
  content: "";
  position: absolute;
  width: 16px;
  height: 2px;
  background-color: #333;
  top: 9px;
  transition: transform 0.3s;
}

.sidebar .toggle-btn::before {
  transform: translateY(-5px);
}

.sidebar .toggle-btn::after {
  transform: translateY(5px);
}

.sidebar .menu {
  list-style: none;
  padding: 20px;
}

.sidebar .menu li {
  margin-bottom: 10px;
}

.sidebar .menu li a {
  color: #fff;
  text-decoration: none;
}

#toggle:checked ~ .menu {
  display: none;
}

#toggle:checked ~ .toggle-btn::before {
  transform: translateY(0) rotate(45deg);
}

#toggle:checked ~ .toggle-btn::after {
  transform: translateY(0) rotate(-45deg);
}