实例：纯CSS实现奥运五环
技术栈：HTML+CSS
效果：
源码：
【HTML】
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>纯CSS实现奥运五环</title>
<link rel="stylesheet" href="249.css">
</head>
<body>
<div class="rings">
<div class="ring ring-blue"></div>
<div class="ring ring-yellow"></div>
<div class="ring ring-black"></div>
<div class="ring ring-green"></div>
<div class="ring rin