<!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.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 mt-3">
<h2>按钮大小</h2>
<button type="button" class="btn btn-primary btn-lg">大型</button>
<button type="button" class="btn btn-primary btn-md">默认</button>
<button type="button" class="btn btn-primary btn-sm">小型</button>
</div>
</body>
</html>