<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.cn/w3css/4/w3.css">
<body>
<div class="w3-container">
<h2>带额外填充的按钮</h2>
<p>
<button class="w3-button w3-black w3-padding-small">按钮</button>
<button class="w3-button w3-black">按钮</button>
<button class="w3-button w3-black w3-padding-large">按钮</button>
</p>
<p>
<button class="w3-btn w3-black w3-padding-small">按钮</button>
<button class="w3-btn w3-black">按钮</button>
<button class="w3-btn w3-black w3-padding-large">按钮</button>
</p>
</div>
</body>
</html>