body {
  background-color: teal;
  font-family: 'Tahoma', sans-serif;
  margin: 0;
  padding: 0;
}

nav {
  margin: 1rem auto;
  width: 400px;
  text-align: center;
}

nav a {
  margin: 0 0.5rem;
  text-decoration: none;
  font-weight: bold;
  color: black;
}

.window {
  margin: 2rem auto;
  width: 400px;
}