css 背景底部圆角【代码片段】

.box { position: relative; }

 .box::before { content: ''; 

position: absolute; 

top: 0; left: 0; height: 100%; 

width: 100%; border-bottom-left-radius: 150px;

 border-bottom-right-radius: 150px; 

background: red; z-index: -1; }