html, body {
    background: url(https://sts.omnilogistics.com/adfs/portal/illustration/illustration.jpg?id=F957336DB85A0EF9A1C8354A18AB7EC9BC0A1444F50E26C7BBD4AB6579C1D988) no-repeat center center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}

.login-container { position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); }
.logo-container img { max-width: 30rem; }

@media (min-width: 1200px) { .login-container { max-width: 50rem; } }
@media (max-width: 767px) { .login-container { width: calc(100vw - 2rem); } }