.loading {
    width: 18px;
    height: 18px;
    border: 2px solid rgba(255,255,255,.3);
    border-top: 2px solid #fff;
    border-radius: 50%;
    display: inline-block;
    animation: spin .8s linear infinite;
    vertical-align: middle;
    margin-right: 8px;
}

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