body {
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  color: #333;
  max-width: 960px;
  margin: 0 auto;
  padding-left: 240px;
  background-color: #fafafa;
}
h1, h2, h3 {
  color: #2c3e50;
}
h1 {
  text-align: center;
  margin-bottom: 30px;
  border-bottom: 2px solid #3498db;
  padding-bottom: 10px;
}
h2 {
  margin-top: 30px;
  border-left: 4px solid #3498db;
  padding-left: 10px;
}
footer {
  margin-top: 40px;
  text-align: center;
  color: #7f8c8d;
  font-size: 0.9em;
}
.nav-fixed {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: 220px;
  padding: 20px;
  background-color: #2c3e50;
  color: white;
  box-shadow: 2px 0 5px rgba(0,0,0,.1);
  overflow-y: auto;
}
.nav-fixed a {
  color: #ecf0f1;
  text-decoration: none;
  display: block;
  padding: 10px 0;
  transition: all 0.3s ease;
}
.nav-fixed a:hover {
  background-color: #34495e;
  padding-left: 10px;
}
.nav-title {
  font-weight: bold;
  margin-bottom: 10px;
}