html, body {
    height: 100%;
    padding: 0;
    margin: 0;
}

body {
    background: url("/img/login-bg.jpg") no-repeat center;
    background-size: cover;
    display: flex;
    align-items: center;        /* vertical */
    /*justify-content: center;    !* horizontal *!*/
}

#login-form {
    position: relative;
    margin: 0 auto;
    max-width: 800px;
    background-color: #fafafa;
    padding: 5em 3em 4em;

    box-shadow:
        /*0 4px 6px hsla(0, 0%, 0%, .5),*/
        0 10px 20px 3px hsla(0, 0%, 0%, .5);
}

#login-form .logo {
    width: auto;
    max-height: 40px;
}