.overlay {
    display: none;
}

.overlay.show {
    display: block;
    position: fixed;
    z-index: 100000;
    background-image: url("../spinner.gif");
    background-color: #666;
    opacity: 0.8;
    background-repeat: no-repeat;
    background-position: center;
    left: 0;
    bottom: 0;
    right: 0;
    top: 0;
    background-size: 18vh;
}