/* ===== 基础变量 ===== */
:root {
  --accent-color: #607d8b;
  --accent-light: #90a4ae;
  --accent-dark: #455a64;
  --text-primary: #333;
  --text-secondary: #666;
  --text-muted: #999;
  --bg-primary: #fff;
  --bg-secondary: #f5f7f8;
  --bg-tertiary: #eceff1;
  --border-color: #e0e6e8;
  --link-color: #607d8b;
  --link-hover: #455a64;
  --max-width: 1400px;
  --content-width: 900px;
  --sidebar-width: 320px;
  --gap: 24px;
  --radius: 4px;
}

/* ===== 重置样式 ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--bg-primary);
}

a {
  color: var(--link-color);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--link-hover);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

ul, ol {
  list-style: none;
}

/* ===== 布局容器 ===== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--gap);
}

.main-wrapper {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--gap);
}

/* ===== Header ===== */
.header {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--gap);
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-color);
}

.logo span {
  color: var(--text-primary);
}

.nav {
  display: flex;
  gap: 32px;
}

.nav a {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
}

.nav a:hover,
.nav a.active {
  color: var(--accent-color);
}

.search-box {
  position: relative;
}

.search-box input {
  width: 240px;
  padding: 8px 16px 8px 36px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  font-size: 0.9rem;
  background: var(--bg-secondary);
  transition: border-color 0.2s;
}

.search-box input:focus {
  outline: none;
  border-color: var(--accent-color);
}

.search-box::before {
  content: "🔍";
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.85rem;
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  background: var(--bg-secondary);
  padding: 12px 0;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.breadcrumb a {
  color: var(--text-secondary);
}

.breadcrumb a:hover {
  color: var(--accent-color);
}

.breadcrumb span {
  margin: 0 8px;
  color: var(--text-muted);
}

/* ===== Hero Section ===== */
.hero {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  padding: 60px var(--gap);
  margin-bottom: var(--gap);
  border-radius: var(--radius);
}

.hero-title {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
  line-height: 1.3;
}

.hero-desc {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 700px;
  margin-bottom: 32px;
}

.hero-features {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--gap);
}

.hero-feature {
  background: var(--bg-primary);
  padding: 24px;
  border-radius: var(--radius);
  border-left: 4px solid var(--accent-color);
}

.hero-feature h3 {
  font-size: 1.1rem;
  color: var(--accent-color);
  margin-bottom: 8px;
}

.hero-feature p {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

/* ===== Section Title ===== */
.section-title {
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 20px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--accent-color);
  display: inline-block;
}

/* ===== Content Grid ===== */
.content-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--gap);
  margin-bottom: var(--gap);
}

.content-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  overflow: hidden;
  transition: box-shadow 0.2s, transform 0.2s;
}

.content-card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
  transform: translateY(-2px);
}

.card-image {
  width: 100%;
  height: 180px;
  background: var(--bg-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  font-size: 3rem;
}

.card-body {
  padding: 20px;
}

.card-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
  line-height: 1.4;
}

.card-meta {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.card-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===== Category Header ===== */
.category-header {
  background: var(--bg-secondary);
  padding: 40px var(--gap);
  margin-bottom: var(--gap);
  border-radius: var(--radius);
  text-align: center;
}

.category-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.category-desc {
  font-size: 1rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 20px;
}

.category-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.category-stats span strong {
  color: var(--accent-color);
  font-size: 1.2rem;
}

/* ===== Article Layout ===== */
.article-container {
  display: grid;
  grid-template-columns: 1fr var(--sidebar-width);
  gap: var(--gap);
}

.article-main {
  background: var(--bg-primary);
}

.article-header {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border-color);
}

.article-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.4;
  margin-bottom: 16px;
}

.article-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.article-meta span {
  display: flex;
  align-items: center;
  gap: 6px;
}

.article-content {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-primary);
}

.article-content h2 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 40px 0 20px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border-color);
}

.article-content h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 28px 0 14px;
}

.article-content p {
  margin-bottom: 16px;
}

.article-content ul,
.article-content ol {
  margin-bottom: 16px;
  padding-left: 24px;
}

.article-content ul {
  list-style: disc;
}

.article-content ol {
  list-style: decimal;
}

.article-content li {
  margin-bottom: 8px;
}

.article-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  font-size: 0.95rem;
}

.article-content th,
.article-content td {
  padding: 12px 16px;
  text-align: left;
  border: 1px solid var(--border-color);
}

.article-content th {
  background: var(--bg-secondary);
  font-weight: 600;
  color: var(--text-primary);
}

.article-content tr:nth-child(even) {
  background: var(--bg-secondary);
}

/* ===== Info Box ===== */
.info-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 20px;
  margin: 24px 0;
}

.info-box-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--accent-color);
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

.info-box-list {
  font-size: 0.9rem;
}

.info-box-list li {
  padding: 6px 0;
  border-bottom: 1px dashed var(--border-color);
}

.info-box-list li:last-child {
  border-bottom: none;
}

.info-box-list a {
  color: var(--link-color);
}

/* ===== Sidebar ===== */
.sidebar {
  position: sticky;
  top: 80px;
  height: fit-content;
}

.sidebar-section {
  background: var(--bg-secondary);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: var(--gap);
}

.sidebar-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--accent-color);
}

.sidebar-list {
  font-size: 0.9rem;
}

.sidebar-list li {
  padding: 10px 0;
  border-bottom: 1px solid var(--border-color);
}

.sidebar-list li:last-child {
  border-bottom: none;
}

.sidebar-list a {
  color: var(--text-secondary);
  display: block;
}

.sidebar-list a:hover {
  color: var(--accent-color);
}

/* TOC Navigation */
.toc-nav {
  font-size: 0.9rem;
}

.toc-nav li {
  padding: 8px 0;
}

.toc-nav a {
  color: var(--text-secondary);
  display: block;
  padding-left: 12px;
  border-left: 2px solid transparent;
}

.toc-nav a:hover,
.toc-nav a.active {
  color: var(--accent-color);
  border-left-color: var(--accent-color);
}

.toc-nav .toc-h2 {
  padding-left: 12px;
}

.toc-nav .toc-h3 {
  padding-left: 24px;
  font-size: 0.85rem;
}

/* ===== Three Column Section ===== */
.three-column {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--gap);
  margin: var(--gap) 0;
}

.column-section {
  background: var(--bg-secondary);
  border-radius: var(--radius);
  padding: 20px;
}

.column-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--accent-color);
}

.column-list {
  font-size: 0.9rem;
}

.column-list li {
  padding: 10px 0;
  border-bottom: 1px solid var(--border-color);
}

.column-list li:last-child {
  border-bottom: none;
}

.column-list a {
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
}

.column-list a:hover {
  color: var(--accent-color);
}

.column-list .num {
  color: var(--accent-color);
  font-weight: 600;
}

/* ===== Pagination ===== */
.pagination {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin: 40px 0;
}

.pagination a,
.pagination span {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 40px;
  height: 40px;
  padding: 0 12px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  font-size: 0.9rem;
  color: var(--text-secondary);
  background: var(--bg-primary);
}

.pagination a:hover {
  border-color: var(--accent-color);
  color: var(--accent-color);
}

.pagination .current {
  background: var(--accent-color);
  border-color: var(--accent-color);
  color: #fff;
}

.pagination .disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ===== References & See Also ===== */
.reference-section {
  background: var(--bg-secondary);
  border-radius: var(--radius);
  padding: 24px;
  margin: 32px 0;
}

.reference-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.reference-list {
  font-size: 0.9rem;
}

.reference-list li {
  padding: 8px 0;
  color: var(--text-secondary);
}

.reference-list a {
  color: var(--link-color);
}

/* Citation Badge */
.citation {
  display: inline-block;
  font-size: 0.75rem;
  color: var(--accent-color);
  vertical-align: super;
  margin-left: 2px;
}

/* ===== 404 Page ===== */
.error-page {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 60px var(--gap);
}

.error-code {
  font-size: 8rem;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 20px;
  opacity: 0.8;
}

.error-title {
  font-size: 1.8rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.error-desc {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 32px;
  max-width: 400px;
}

.error-actions {
  display: flex;
  gap: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  padding: 12px 24px;
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-weight: 500;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--accent-color);
  color: #fff;
}

.btn-primary:hover {
  background: var(--accent-dark);
  color: #fff;
}

.btn-secondary {
  background: var(--bg-secondary);
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  border-color: var(--accent-color);
  color: var(--accent-color);
}

/* ===== Footer ===== */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 40px 0;
  margin-top: 60px;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--gap);
}

.footer-content {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 32px;
}

.footer-brand {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--accent-color);
  margin-bottom: 12px;
}

.footer-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.footer-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.footer-links {
  font-size: 0.9rem;
}

.footer-links li {
  margin-bottom: 10px;
}

.footer-links a {
  color: var(--text-secondary);
}

.footer-links a:hover {
  color: var(--accent-color);
}

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* ===== Responsive ===== */
@media (max-width: 1024px) {
  .article-container {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--gap);
  }

  .sidebar-section {
    margin-bottom: 0;
  }

  .footer-content {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  :root {
    --gap: 16px;
  }

  .header-inner {
    flex-wrap: wrap;
    height: auto;
    padding: 12px var(--gap);
    gap: 12px;
  }

  .nav {
    order: 3;
    width: 100%;
    gap: 20px;
    justify-content: center;
    padding-top: 8px;
    border-top: 1px solid var(--border-color);
  }

  .search-box {
    order: 2;
  }

  .search-box input {
    width: 180px;
  }

  .hero {
    padding: 40px var(--gap);
  }

  .hero-title {
    font-size: 1.8rem;
  }

  .hero-features {
    grid-template-columns: 1fr;
  }

  .content-grid {
    grid-template-columns: 1fr;
  }

  .three-column {
    grid-template-columns: 1fr;
  }

  .sidebar {
    grid-template-columns: 1fr;
  }

  .footer-content {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .article-title {
    font-size: 1.5rem;
  }

  .category-stats {
    flex-direction: column;
    gap: 12px;
  }

  .error-code {
    font-size: 5rem;
  }

  .error-actions {
    flex-direction: column;
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: 1.5rem;
  }

  .section-title {
    font-size: 1.2rem;
  }

  .article-content h2 {
    font-size: 1.3rem;
  }

  .pagination {
    flex-wrap: wrap;
  }
}