<div class="layout">
  <input type="checkbox" id="sidebar-toggle" class="sidebar-toggle" hidden>
  <label for="sidebar-toggle" class="hamburger">&#9776;</label>
<p><aside class="sidebar">
<ul>
<li><a href="#">首页</a></li>
<li><a href="#">产品</a></li>
<li><a href="#">关于</a></li>
<li><a href="#">联系</a></li>
</ul>
</aside></p><p><main class="main-content">
<h1>主内容区</h1>
<p>这里是页面主要内容。</p>
</main>
</div></p>

.layout {
  display: flex;
  min-height: 100vh;
}
<p>.sidebar {
width: 240px;
background: #333;
color: white;
transition: transform 0.3s ease;
}</p><p>.sidebar ul {
list-style: none;
padding: 0;
margin: 0;
}</p><p>.sidebar a {
display: block;
padding: 15px;
color: white;
text-decoration: none;
}</p><p>.sidebar a:hover {
background: #555;
}</p><p>.main-content {
flex: 1;
padding: 20px;
background: #f4f4f4;
}</p><p>/<em> 汉堡按钮样式 </em>/
.hamburger {
position: absolute;
top: 15px;
left: 15px;
font-size: 24px;
cursor: pointer;
display: none;
z-index: 10;
}</p><p>/<em> 小屏幕下的响应式处理 </em>/
@media (max-width: 768px) {
.hamburger {
display: block;
}</p><p>.sidebar {
position: fixed;
top: 0;
left: 0;
height: 100%;
transform: translateX(-100%);
}</p><p>/<em> 当复选框被勾选时，展开侧边栏 </em>/
.sidebar-toggle:checked + .hamburger + .sidebar {
transform: translateX(0);
}</p><p>.main-content {
margin-left: 0;
}
}</p>

.overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.5);
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
}
<p>.sidebar-toggle:checked ~ .overlay {
opacity: 1;
visibility: visible;
}</p>