body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background-color: #ffffff;
  color: #333;
}

header {
  background-color: #87ceeb; /* 天蓝色 */
  color: white;
  padding: 1rem;
  text-align: center;
}

nav {
  background-color: #228B22; /* 春天的绿树绿色 */
  padding: 0.5rem;
  text-align: center;
}

nav a {
  color: white;
  margin: 0 1rem;
  text-decoration: none;
  font-weight: bold;
}

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

main {
  padding: 2rem;
  max-width: 800px;
  margin: auto;
}

footer {
  background-color: #f0f0f0;
  color: #666;
  text-align: center;
  padding: 1rem;
  margin-top: 2rem;
}