На codepen, если вы измените представление на режим отладки , откроется новая вкладка с полноэкранным просмотром страницы.
Просмотрите исходный код, и вы увидите, что страница содержит обычные HTML-теги head и body.
Пример
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Test - YouTube Play Pause Button</title>
<style>
body {
background: #111;
text-align: center;
}
svg {
margin-top: 45vh;
width: 40px;
height: 40px;
cursor: pointer;
}
</style>
</head>
<body translate="no">
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="16px" height="16px" viewBox="0 0 16 16" version="1.1">
<!-- bar 1 -->
<path fill="#D8D8D8" d="M0,0 L6,0 L6,16 L0,16 L0,0 Z" id="bar1">
<animate xlink:href="#bar1"
attributeName="d"
from="M0,0 L6,0 L6,16 L0,16 L0,0 Z"
to="M0,0 L6,3.20001221 L6,12.7999878 L0,16 L0,0 Z"
dur="0.3s"
fill="freeze"
begin="startAnimation.begin" />
<animate xlink:href="#bar1"
attributeName="d"
from="M0,0 L6,3.20001221 L6,12.7999878 L0,16 L0,0 Z"
to="M0,0 L6,0 L6,16 L0,16 L0,0 Z"
dur="0.3s"
fill="freeze"
begin="reverseAnimation.begin" />
</path>
<!-- horizontal line -->
<path fill="#D8D8D8" d="M10,0 L16,0 L16,16 L10,16 Z" id="bar2">
<animate attributeName="d"
from="M10,0 L16,0 L16,16 L10,16 Z"
to="M5.9944458,3.20001221 L15,8 L15,8 L5.9944458,12.7999878 Z"
dur="0.3s"
fill="freeze"
begin="startAnimation.begin" />
<animate attributeName="d"
from="M5.9944458,3.20001221 L15,8 L15,8 L5.9944458,12.7999878 Z"
to="M10,0 L16,0 L16,16 L10,16 Z"
dur="0.3s"
fill="freeze"
begin="reverseAnimation.begin" />
</path>
<!-- controls -->
<!-- these are on top of the visible icon. Their radius changes depending on which is active
Opacity is set to 0 so you can't see them-->
<circle cx="16" cy="16" r="16" fill-opacity="0">
<animate dur="0.01s" id="startAnimation" attributeName="r" values="16; 0" fill="freeze" begin="click" />
<animate dur="0.01s" attributeName="r" values="0; 16" fill="freeze" begin="reverseAnimation.end" />
</circle>
<circle cx="16" cy="16" r="0" fill-opacity="0">
<animate dur="0.001s" id="reverseAnimation" attributeName="r" values="16; 0" fill="freeze" begin="click" />
<animate dur="0.001s" attributeName="r" values="0; 16" begin="startAnimation.end" fill="freeze" />
</circle>
</svg>
</body>
</html>