body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  margin: 0;
  background: #0b1020;
  color: #f5f5f5;
}
header {
  background: #151b32;
  padding: 1rem;
  text-align: center;
}
header nav {
  margin-top: 0.75rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}
header nav button {
  padding: 0.35rem 0.9rem;
  border-radius: 999px;
  border: none;
  background: #2f3ad7;
  color: #fff;
}
main {
  padding: 1rem;
}
section {
  display: none;
}
section.active {
  display: block;
}
footer {
  padding: 0.75rem;
  text-align: center;
  background: #111625;
  font-size: 0.8rem;
}