html, body {
    margin:0;
    color:#999;
    text-align: center;
    display:flex;
    justify-content: center;
    align-items: center;
    height:90%;
}
body::after{
    content: "";
    position: absolute;
    top:0;
    left:0;
    bottom: 0;
    right: 0;
    background-image:url(open_bg.jpg);
    background-size: cover;
    z-index: -1;
    background-position:center center;
    opacity: 0.05;
}
div {
    font-size:100px;
}