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<!DOCTYPE html>
<html lang="en">
<head>
  <title>Bootstrap Example</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.2/dist/css/bootstrap.min.css" rel="stylesheet">
  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.2/dist/js/bootstrap.bundle.min.js"></script>
</head>
<body>
​
<div class="container-fluid mt-3">
  <h1>基本网格结构</h1>
  <p>请调整浏览器窗口大小来查看效果。</p>
  <p>当屏幕宽度小于 576px 时，第一行、第二行和第三行会自动堆叠在一起。</p>
  
  <!-- 控制列宽，以及它们在不同设备上的显示方式 -->
  <div class="row">
    <div class="col-sm-6 bg-primary text-white">50%</div>
    <div class="col-sm-6 bg-dark text-white">50%</div>
  </div>
  <br>
    
  <div class="row">
    <div class="col-sm-4 bg-primary text-white">33.33%</div>
    <div class="col-sm-4 bg-dark text-white">33.33%</div>
    <div class="col-sm-4 bg-primary text-white">33.33%</div>
  </div>
  <br>
​
  <!-- 或者让 Bootstrap 自动处理布局 -->
  <div class="row">
    <div class="col-sm bg-primary text-white">25%</div>
    <div class="col-sm bg-dark text-white">25%</div>
    <div class="col-sm bg-primary text-white">25%</div>
    <div class="col-sm bg-dark text-white">25%</div>
  </div>
  <br>
    
  <div class="row">
    <div class="col bg-primary text-white">25%</div>
    <div class="col bg-dark text-white">25%</div>
    <div class="col bg-primary text-white">25%</div>
    <div class="col bg-dark text-white">25%</div>
  </div>
</div>
​
</body>
</html>
​