css3画半圆的两种方法

<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    * {margin: 0; padding: 0;}
    .clearfix{zoom:1;/*为IE6，7的兼容性设置*/}
    .clearfix:after {
      content: '.';
      display: block;
      height: 0;
      clear: both;
      visibility: hidden;
    }
    ul li {
      list-style: none;
      float: left;
      margin: 50px 0 50px 20px;
      text-align: center;
    }
    li {
      background: red;
    }
    h2 {
      margin-top: 20px;
    }
    .circle1 {
      width: 100px;
      height: 50px;
      border-radius: 50px 50px 0 0;
      line-height: 50px;
    }
    .circle2 {
      width: 50px;
      height: 100px;
      border-radius: 0 50px 50px 0;
      line-height: 100px;
    }
    .circle3 {
      width: 100px;
      height: 50px;
      border-radius: 0 0px 50px 50px;
      line-height: 50px;
    }
    .circle4 {
      width: 50px;
      height: 100px;
      border-radius: 50px 0 0 50px;
      line-height: 100px;
    }
    .circle5 {
      width: 100px;
      height: 100px;
      border-radius: 50px;
      line-height: 100px;
    }
    .demo { /*左半圆*/
      position:absolute; /*clip 属性剪裁绝对定位元素。也就是说，只有 position:absolute 的时候才是生效的。*/
      width: 100px;
      height: 100px;
      border-radius: 50px;
      /* line-height: 50px; */
      clip: rect(0px 50px 100px 0px); /*唯一合法的形状值是：rect (top, right, bottom, left)*/
    }
    .right-circle { /*右半圆*/
      left: 200px;
      clip: rect(0px 100px 100px 50px); /*唯一合法的形状值是：rect (top, right, bottom, left)*/
    }
  </style>
</head>
<body>
  <div>
    <h2>用border-radius实现半圆</h2>
    <ul class="clearfix">
      <li class="circle1">上边圆</li>
      <li class="circle2">左边圆</li>
      <li class="circle3">下边圆</li>
      <li class="circle4">左边圆</li>
      <li class="circle5">全圆</li>
    </ul>
    <hr>
    <h2>css3的clip 方法剪裁实现半圆</h2>
    <p style="color: red;">clip 属性剪裁绝对定位元素。也就是说，只有 position:absolute 的时候才是生效的。唯一合法的形状值是：rect (top, right, bottom, left)</p>
    <ul class="clearfix" style="position: relative;">
      <li class="demo">左半圆</li>
      <li class="demo right-circle">右半圆</li>
      <li></li>
    </ul>
  </div>
</body>
</html>
效果图：
感兴趣的朋友可以去熟试下！！！