答案 0 :(得分:8)
我使用了box-shadow
的2个div我添加了border
以便理解
body {
background:url(https://placeimg.com/640/480/any);
}
.out {
width: 455px;
height: 275px;
border: 1px solid red;
position: relative;
overflow: hidden;
margin: 20px;
}
.in {
width: 550px;
height: 550px;
border: 1px solid green;
position: absolute;
left: 200px;
border-radius: 50%;
box-shadow: 0 0 0 500px white; /* this is the white background */
}
.bottom .in {
bottom: 0;
left: 200px;
}

<div class="out">
<div class="in">
</div>
</div>
<div class="out bottom">
<div class="in">
</div>
</div>
&#13;