#loader {
    position: fixed;
    top: 50%;
    left: 50%;
    /* bring your own prefixes */
    transform: translate(-50%, -50%);
    z-index: 99999;

    display: none;

    border: 16px solid #f3f3f3; /* Light grey */
    border-top: 16px solid #217826; /* Blue */
    border-radius: 50%;
    width: 60px;
    height: 60px;
    animation: spin 2s linear infinite;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}

#overlay {
    display: none;
    position: fixed;
    left: 0;
    top: 0;
    height: 100%;
    width: 100%;
    background-color: black;
    opacity: 0.5;
    z-index: 999;
}