Edit in JSFiddle

div {
    width: 100px;
    height: 100px;
    background: #000;
    color: #fff;
    line-height: 100px;
    text-align: center;
    font-size: 2rem;
    animation: gira 2s linear infinite;
}

@keyframes gira {
    to {
      transform: rotate(360deg);  
    }
}