<div></div>
html,body {
width: 100%;
height: 100%;
margin: 0;
padding: 0;
}
div {
width:100px;
border:100px solid transparent;
border-bottom:100px solid hotpink;
margin: 0 auto; /*水平居中*/
position: relative; /*脱离文档流*/
top: 50%; /*偏移*/
margin-top: -100px;
}