.login-ui {
    display: block;
    border: none;
    background: #141414bf;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    position: fixed;
    z-index: 99999;
}

    .login-ui iframe {
        border: solid 2px #ccc;
        border-radius: 8px;
        background: #fff;
        width: 640px;
        height: 500px;
        top: calc(50% - 250px - 50px);
        left: calc(50% - 320px);
        position: fixed;
    }