body {
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  color: #333;
  max-width: 1100px;
  margin: 0 auto;
  padding-left: 260px;
  background-color: #fafafa;
}
h1, h2, h3, h4 {
  color: #2c3e50;
}
h1 {
  text-align: center;
  margin: 20px 0 30px;
  border-bottom: 2px solid #3498db;
  padding-bottom: 10px;
}
h2 {
  margin-top: 30px;
  border-left: 4px solid #3498db;
  padding-left: 10px;
}
h3 {
  margin-top: 20px;
  color: #2980b9;
}
h4 {
  margin-top: 16px;
}
ul, ol {
  padding-left: 22px;
}
li {
  margin-bottom: 6px;
}
pre, code {
  background-color: #f4f4f4;
  border-radius: 4px;
  font-family: Consolas, Monaco, monospace;
  font-size: 0.9em;
}
.code-wrap {
  position: relative;
  margin: 12px 0;
}
pre {
  padding: 10px 12px 36px 12px;
  border-left: 3px solid #3498db;
  overflow-x: auto;
  margin: 0;
}
.code-copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 6px 12px;
  background: #3498db;
  color: white;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 0.85em;
}
.code-copy-btn:hover {
  background: #217dbb;
}
.code-copy-btn.copied {
  background: #27ae60;
}
code {
  padding: 2px 6px;
}
.note {
  background-color: #fff8e1;
  border-left: 4px solid #ffc107;
  padding: 10px 12px;
  margin: 15px 0;
  border-radius: 0 4px 4px 0;
  font-size: 0.95em;
}
.tip {
  background-color: #e3f2fd;
  border-left: 4px solid #2196f3;
  padding: 10px 12px;
  margin: 10px 0;
  border-radius: 0 4px 4px 0;
  font-size: 0.95em;
}
table {
  border-collapse: collapse;
  width: 100%;
  margin: 12px 0;
  font-size: 0.95em;
}
th, td {
  border: 1px solid #ddd;
  padding: 8px 12px;
  text-align: left;
}
th {
  background-color: #3498db;
  color: white;
}
tr:nth-child(even) {
  background-color: #f9f9f9;
}
a {
  color: #1976d2;
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}
footer {
  margin: 40px 0 20px;
  text-align: center;
  color: #7f8c8d;
  font-size: 0.9em;
}
.chapter-nav {
  position: fixed;
  top: 20px;
  left: 20px;
  width: 200px;
  background: #2c3e50;
  padding: 16px 14px;
  border-radius: 6px;
  color: white;
  box-shadow: 0 3px 6px rgba(0,0,0,0.1);
}
.chapter-nav h3 {
  color: #ecf0f1;
  margin-top: 0;
  margin-bottom: 10px;
  font-size: 1em;
  font-weight: bold;
}
.chapter-nav a {
  display: block;
  padding: 6px 0;
  color: #ecf0f1;
  text-decoration: none;
}
.chapter-nav a:hover {
  background: rgba(255,255,255,0.1);
  padding-left: 6px;
}
/* 一级菜单：六大章节 */
.chapter-nav a.nav-top {
  font-size: 0.98em;
  font-weight: 600;
  padding: 6px 0 4px 0;
  border-bottom: 1px solid rgba(255,255,255,0.08);
  margin-bottom: 2px;
}
.chapter-nav a.nav-top:hover {
  padding-left: 6px;
}
/* 二级菜单：小节 */
.chapter-nav a.nav-sub {
  font-size: 0.85em;
  font-weight: 400;
  color: #bdc3c7;
  padding: 4px 0 4px 14px;
}
.chapter-nav a.nav-sub:hover {
  color: #ecf0f1;
  padding-left: 18px;
}
/* 代码对应示例图 */
.fig-wrap {
  margin: 14px 0;
  text-align: center;
}
.fig-wrap img {
  max-width: 100%;
  height: auto;
  border-radius: 6px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}
.fig-cap {
  font-size: 0.9em;
  color: #666;
  margin-top: 6px;
}