/* Make the html body cover the entire (visual) viewport with no scroll bars. */
html, body { 
    padding: 0; 
    margin: 0; 
    overflow: hidden; 
    height: 100%; 
}

body { 
    display: flex; 
    justify-content: center; 
    align-items: center; 
    background-color: rgb(151, 204, 232);
}

#screen { 
    width: 800px; 
    height: 600px; 
}

@media screen and (max-width: 800px) {
    body {
        display: block;
    }
}