body {
    padding: 0;
}

header {
    background-color: rgba(0, 0, 0, 0.75);
}

main {
    background-color: rgba(0, 0, 0, 0.5);
}

footer {
    background-color: rgba(0, 0, 0, 0.25);
}

@media(min-width: 800px) {
    body {
        height: 100vh;
        display: grid;
        grid-template-rows: auto 40px;
        grid-template-columns: 225px auto;
    }

    header {
        grid-row: span 2;
    }

    main {
        overflow-y: scroll;
    }
}