body {
  font-family: system-ui, -apple-system, sans-serif;
  margin: 40px auto;
  max-width: 800px;
  line-height: 1.7;
  color: #333;
  background-color: #fff;
  padding: 0 20px;
}

header {
  border-bottom: 4px double #0b3d91;
  margin-bottom: 20px;
  padding-bottom: 5px;
}

h1, h2 {
  color: #0b3d91;
}

h1 {
  font-size: 2.2em;
  margin-bottom: 0.2em;
}

h2 {
  font-size: 1.5em;
  margin-top: 1.5em;
}

nav {
  margin-bottom: 20px;
}

nav a {
  text-decoration: none;
  color: #0b3d91; /* 深蓝，与标题统一 */
  margin-right: 15px;
}

nav a:hover {
  color: #1155cc; /* 悬停时稍亮一点 */
  text-decoration: underline;
}

footer {
  margin-top: 40px;
  font-size: 0.9em;
  color: #666;
  border-top: 1px solid #ddd;
  padding-top: 10px;
}