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

.spinner:before {
    content: '';
    box-sizing: border-box;
    position: absolute;
    top: 15em;
    left: 50%;
    width: 50px;
    height: 50px;
    margin-top: -10px;
    margin-left: -10px;
    border-radius: 50%;
    border-top: 5px solid var(--core-theme-color);
    border-right: 5px solid transparent;
    animation: spinner .6s linear infinite;
}