div {
position: relative;
width: 200px;
height: 200px;
background: #000;
overflow: hidden;
border-radius: 50%;
animation: ROTATION 5s linear infinite;
}
div:before {
position: absolute;
display: block;
content: "";
top: 0; left: 0;
width: 50%; height: 100%;
background: #999;
}
div:after {
position: absolute;
display: block;
content: "";
top: 0; right: 0;
width: 50%; height: 100%;
background: #f00;
}
@keyframes ROTATION {
0% {
transform: rotate(0deg);
}
100% {
transform: rotate(360deg);
}
}