代码示例：（标识：bs_flex-column-responsive）
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.bundle.js"></script>
</head>
<body>
<div class="p-4">
<h2>垂直方向</h2>
<p>使用 .flex-column 垂直显示 flex 项目（堆叠）。</p>
<p>使用 .flex-sm|md|lg|xl-column 在不同屏幕尺寸上实现此效果。</p>
<p><code>.flex-column</code>:</p>
<div class="d-flex flex-column mb-3">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>
<p><code>.flex-sm-column</code>:</p>
<div class="d-flex flex-sm-column mb-3">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>
<p><code>.flex-md-column</code>:</p>
<div class="d-flex flex-md-column mb-3">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>
<p><code>.flex-lg-column</code>:</p>
<div class="d-flex flex-lg-column mb-3">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>
<p><code>.flex-xl-column</code>:</p>
<div class="d-flex flex-xl-column mb-3">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>
<p><code>.flex-xxl-column</code>:</p>
<div class="d-flex flex-xxl-column mb-3">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>
</div>
</body>
</html>
