.loader {
    width: 5em;
    height: 5em;
    border-radius: 50%;
    border: 0.25em solid transparent;
    border-top-color: #333;
    -webkit-animation: spinner 1.5s linear infinite;
            animation: spinner 1.5s linear infinite;
    margin: 30px auto;
    display: none;
}

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

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