* {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    margin-top: 0;
}

html,
body,
div {
    margin: 0;
    padding: 0;
}

body {
    background-color: darkgreen;
}

main {
    background: #dddddd;
    padding: 20px;

    width: 100%;
}

pre {
    padding: 20px;
    background-color: #aaa;
    border: 1px solid black;
    border-radius: 12px;
}

@media (min-width: 700px) {
    body {
        background-image: url("/assets/background.jpg");
        background-repeat: no-repeat;
        background-size: cover;
    }

    main {
        margin-top: 50px;
        margin-bottom: 50px;
        margin-left: auto;
        margin-right: 20px;
        max-width: 600px;
        border: solid 3px black;
        border-radius: 25px;
    }
}