body {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
}
nav {
  background: #eee;
}
nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 1em;
}
nav a {
  text-decoration: none;
  color: inherit;
  padding: 1em;
  display: block;
}
nav a.active {
  background-color: #999;
  color: #fff;
}
main {
  padding: 1em;
}