📅  最后修改于: 2022-03-11 14:55:40.101000             🧑  作者: Mango
div {
height: 300px;
background: red;
position: relative;
}
div:before {
content: '';
position: absolute;
top: 1; right: 1;
border-top: 80px solid white;
border-left: 80px solid red;
width: 0;
}