html {
    background: url(img.jpeg) no-repeat center center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}

#main-wrapper {  
    position: absolute;
    width:100%;
    padding: 0 32px;
}

#main-center {  
    max-width: 340px;
    margin: 64px auto 0 auto;

}

#main-center .card {
    background: rgba(255, 255, 255, .8);
    border-radius: 0.5rem;
}

#main-center .card img{
    border-radius: 0.5rem 0.5rem 0 0;
}