#share-modal {
    position: fixed;
    z-index: 999;
}

#share-modal:before {
    content: "";
    display: block;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: #000;
    opacity: 0.2;
    z-index: -1;
}