styles.css

html {
  box-sizing: border-box;
  font: 16px/1.5 "Helvetica Neue", Helvetica, Arial, sans-serif;
  border-top: 0.75rem solid #808;
}

*, *::before, *::after {
  box-sizing: inherit;
}

body {
  margin: 0 auto;
  padding: 0 0 2rem;
  max-width: 40rem;
}

header h1 {
  margin: 0 0 1rem -0.25rem;
  font-size: 5rem;
  line-height: 0.75;
}

header h1 a:link, header h1 a:visited {
  color: #808;
}

nav ul {
  padding: 0;
  list-style: none;
}

footer {
  font-size: 0.75rem;
}

pre {
  padding: 1rem;
  font: 15px Consolas, monospace;
  background: #fef;
  overflow: auto;
}

a:link {
  text-decoration: none;
}

a:link, a:visited {
  color: #a0a;
}

a:focus, a:hover, a:active {
  background: #fdd;
}

@media (min-width: 60rem) {
  body {
    max-width: 56rem; /* 15 + 1 + 40 */
    display: grid;
    grid-template-rows: auto auto minmax(0, 1fr);
    grid-template-columns: 15rem auto;
    grid-gap: 0 1rem;
  }

  header {
    grid-column: 1;
    grid-row: 1;
  }

  nav {
    grid-column: 1;
    grid-row: 2;
  }

  main {
    grid-column: 2;
    grid-row: 1 / 4;
  }

  footer {
    grid-column: 1;
    grid-row: 3;
  }
}