css圆形样式

.border{
width: 100px;
height: 100px;
border-width: 50px;
border-style: solid;
border-top-color: #f00;
border-right-color: #f00;
border-bottom-color: #00f;
border-left-color: #00f;
border-radius: 50%;
transform: rotate(-45deg);
}