/* Layout… */
body * {
  padding: 1em;
}

header {
  display: flex;
  align-items: center;
}

h1 {
  margin: 0;
  padding: 0;
}

nav {
  flex-basis: 100%;
  margin: 0 0 0 0.5em;
}

main {
  display: flex;
}

main div {
  flex-basis: 75%;
  margin: 0 1em 0 0;
  padding: 0;
}

aside {
  flex-basis: 25%;
}

section:not(:last-child) {
  margin-bottom: 0.5em;
}

/* Colors… */
header,
footer {
  background-color: Gainsboro;
}

nav,
section,
aside {
  background-color: Silver;
}

main {
  background-color: WhiteSmoke;
}