.block-ui {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: grey;
    opacity: 0.5;
    z-index: 1002;
}

.block-ui-content {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 1003;
}