html, body { padding: 0; margin: 0; }
.wrapper { display: block; position: relative; width: 100%; height: 100vh; }
.wrapper::after {content: ""; position: absolute;  top: 0; bottom: 0; left: 0; right: 0; background-image: url('bg.png'); background-repeat: no-repeat; background-size: cover; z-index: -1; opacity: 0.2; }
.logo { background: #000; width: 500px; padding: 15px; box-shadow: 1px 1px 1px 0 #000; position: absolute; left: 50%; top: 50%; margin-left: -230px; margin-top: -150px; }
.logo img { width: 100%; height: auto; }

@media(max-width: 797px) {
    .logo { background: #000; width: 300px; margin-left: -150px; }
}