background-image: radial-gradient(200px at 50px 0px, #fff 50px, #4169E1 50px);
这是做内凹圆角的核心代码，就是背景图的radial-gradient，只设置两种颜色，中间不进行过渡渐变。两种颜色叠到一起就是一条实线，看上去就是两个色块的拼接。
1.立体质感圆球
网上看到的一个很有趣的小案例——用radial-gradient制作的立体质感小圆球。
就一行代码！
<span class="egg"></span>
.egg {display: block;margin-top: 30px;width: 100px;height: 100px;border-radius: 50px;background: radial-gradient(at 35px 35px, #FFF, #CCC, #FFF);background: -webkit-radial-gradient(35px 35px, #FFF, #CCC, #FFF);}
http://blog.****.net/playboyanta123/article/details/9303857
2.手动内凹
如下是一种用一个圆和一个方形盒子叠加做出的内凹圆角的的效果。
<div class="something-meaningful brdradius"></div>
<div class="something-meaningful">
<div>
<a href="http://www.w3cplus.com/css3/css-secrets/inner-rounding.html"></a>
</div>
</div>
.something-meaningful {display: inline-block;width: 55px;height: 55px;overflow: hidden;line-height: 130px;background: #655;text-align: center;/* padding: .8em; */position: relative;float: left;}
.brdradius {border-top-left-radius: 45%;}
.something-meaningful> div {width: 100px;height: 100px;background: #fff;border-radius: 5em;position: absolute;top: -46px;left: 2px;/*padding: 1em;*/}
3.我自己也来玩玩
<span class="radius"></span>
.radius {width: 50px;height: 50px;line-height: 100px;display: block;text-align: center;background-image: radial-gradient(200px at 50px 0px, #fff 50px, #4169E1 50px);}
利用个背景色的径向渐变background-image: radial-gradient(200px at 50px 0px, #fff 50px, #4169E1 50px);，
就画出这么一个小内凹角来，想要另外方向的也可以变化。如下的一个完整案例
<ul class="uls">
<li>1
<span class="li-boradiu"></span>
</li>
<li>2
<span class="li-boradiu"></span>
</li>
<li>3</li>
</ul>
.uls{list-style-type: none;*zoom: -1;}
.uls:after{content: "";clear: both;display: block;}
.uls li{display: block;float: left;width: 120px;height: 35px;background-color: #4169E1;text-align: center;line-height: 35px;color: white;/*做上圆角*/border-top-left-radius : 15px; border-top-right-radius : 15px; }
.li-boradiu{display: inline-block;width: 35px;height: 35px;/*background-color: #4169E1;*/background-image: radial-gradient(70px at 17.5px 0, #f00);}
参考资料：radial-gradient CSS3的蛋疼的径向渐变
<!DOCTYPE html>
<html> <head>
<meta charset="UTF-8">
<title>内凹圆角</title>
<meta name="description" content="css3，内凹圆角">
<meta name="author" content="郭菊锋702004176@qq.com"/>
<style type="text/css">
.egg {
display: block;
margin-top: 30px;
width: 100px;
height: 100px;
border-radius: 50px;
background: radial-gradient(at 35px 35px, #FFF, #CCC, #FFF);
background: -webkit-radial-gradient(35px 35px, #FFF, #CCC, #FFF);
} .something-meaningful {
display: inline-block;
width: 55px;
height: 55px;
overflow: hidden;
line-height: 130px;
background: #655;
text-align: center;
/* padding: .8em; */
position: relative;
float: left;
} .brdradius {
border-top-left-radius: 45%;
} .something-meaningful> div {
width: 100px;
height: 100px;
background: #fff;
border-radius: 5em;
position: absolute;
top: -46px;
left: 2px;
/*padding: 1em;*/
} .radius {
width: 50px;
height: 50px;
line-height: 100px;
display: block;
text-align: center;
background-image: radial-gradient(200px at 50px 0px, #fff 50px, #4169E1 50px);
}
.uls{
list-style-type: none;
*zoom: -1;
}
.uls:after{
content: "";
clear: both;
display: block;
}
.uls li{
display: block;
float: left;
width: 120px;
height: 35px;
background-color: #4169E1;
text-align: center;
line-height: 35px;
color: white;
/*做上圆角*/
border-top-left-radius : 15px;
border-top-right-radius : 15px;
}
.li-boradiu{
display: inline-block;
width: 35px;
height: 35px;
/*background-color: #4169E1;*/
background-image: radial-gradient(70px at 17.5px 0, #f00);
}
</style>
</head> <body> <h3>1.网上看到的一个很有趣的小案例——用radial-gradient制作立体质感圆球。</h3>
<!--http://blog.****.net/playboyanta123/article/details/9303857-->
<span class="egg"></span> <!--手动内凹！-->
<h3>2.如下是一种用一个圆和一个方形盒子叠加做出的内凹圆角的的效果。</h3>
<div class="something-meaningful brdradius"></div>
<div class="something-meaningful">
<div>
<a href="http://www.w3cplus.com/css3/css-secrets/inner-rounding.html"></a>
</div>
</div>
<h3 style="clear: both;padding-top: 10px;">3.自己也来玩玩</h3>
<span class="radius"></span>
<p>这样 利用个背景色的径向渐变background-image: radial-gradient(200px at 50px 0px, #fff 50px, #4169E1 50px);，就画出这么一个小内凹角来，想要另外方向的也可以变化。如下的一个完整案例</p>
<ul class="uls">
<li>1
<span class="li-boradiu"></span>
</li>
<li>2
<span class="li-boradiu"></span>
</li>
<li>3</li>
</ul> <a href="http://blog.****.net/playboyanta123/article/details/9303857">参考资料：radial-gradient CSS3的蛋疼的径向渐变</a> </body> </html>
代码实现