section.overlay {
    width: 100%;
    visibility: hidden;
    height: 100%;
    margin: 0;
    z-index: 9999;
    position: fixed;
}
#overlay {
    width: 100%;
    height: 100%;
    display:table;
    background: rgba(0, 0, 0, 0.5);
}
#overlay i {
   display:table-cell;
    vertical-align:middle;
    text-align:center;
    font-size: 50px;
    color: #fff;
}
.spin-big {
    height: 90px;
    width: 90px;
    color: #fff;
 
}