/* Base styles (mobile-first) */
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  line-height: 1.6;
  background-color: #f8f9fa;
  color: #333;
}

header {
  background-color: #003366;
  color: white;
  text-align: center;
  padding: 1rem;
  font-size: 1.5rem;
}

nav {
  background-color: #005599;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  padding: 0.5rem;
}

nav a {
  color: white;
  text-decoration: none;
  margin: 0.5rem;
  font-weight: bold;
  font-size: 1rem;
}

nav a:hover {
  text-decoration: underline;
}

main {
  padding: 1.5rem;
}

main ul {
  padding-left: 1.5rem;
}

footer {
  background-color: #003366;
  color: white;
  text-align: center;
  padding: 1rem;
  font-size: 0.9rem;
  margin-top: 2rem;
}

/* Tablet and up */
@media (min-width: 600px) {
  header {
    font-size: 2rem;
  }

  nav a {
    font-size: 1.1rem;
    margin: 0 1rem;
  }

  main {
    padding: 2rem 3rem;
  }

  footer {
    font-size: 1rem;
  }
}

/* Desktop and up */
@media (min-width: 900px) {
  main {
    max-width: 960px;
    margin: 0 auto;
  }
}