/* ========================================
   Apethon Default Theme - style.css
   ======================================== */

/* --- CSS Variables --- */
:root {
  --color-bg: #ffffff;
  --color-bg-secondary: #fafbfc;
  --color-bg-tertiary: #eef1f5;
  --color-text: #1f2328;
  --color-text-secondary: #656d76;
  --color-text-tertiary: #8b949e;
  --color-border: #d0d7de;
  --color-border-light: #e8ecf0;
  --color-primary: #0969da;
  --color-primary-light: #ddf4ff;
  --color-link: #0969da;
  --color-code-bg: #f6f8fa;
  --color-card-bg: #ffffff;
  --color-card-shadow: rgba(31, 35, 40, 0.04);
  --color-tag-bg: #f0f1f3;
  --color-tag-text: #586069;
  --color-cat-bg: #f0f1f3;
  --color-cat-text: #586069;
  --sidebar-width: 260px;
  --toc-width: 220px;
  --navbar-height: 56px;
  --content-max-width: 800px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --transition: 0.2s ease;
}

[data-theme="dark"] {
  --color-bg: #0d1117;
  --color-bg-secondary: #161b22;
  --color-bg-tertiary: #21262d;
  --color-text: #e6edf3;
  --color-text-secondary: #8b949e;
  --color-text-tertiary: #6e7681;
  --color-border: #30363d;
  --color-border-light: #21262d;
  --color-primary: #58a6ff;
  --color-primary-light: #0d1117;
  --color-link: #58a6ff;
  --color-code-bg: #161b22;
  --color-card-bg: #161b22;
  --color-card-shadow: rgba(0, 0, 0, 0.3);
  --color-tag-bg: #21262d;
  --color-tag-text: #8b949e;
  --color-cat-bg: #21262d;
  --color-cat-text: #8b949e;
}

/* --- Reset & Base --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--navbar-height) + 16px);
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a {
  color: var(--color-link);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { text-decoration: underline; }

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

/* --- Navbar --- */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--navbar-height);
  border-bottom: 1px solid var(--color-border-light);
  z-index: 1000;
  backdrop-filter: blur(8px);
}
[data-theme="dark"] .navbar { background: rgba(13, 17, 23, 0.85); }
[data-theme="light"] .navbar, .navbar { background: rgba(255, 255, 255, 0.85); }

.navbar-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  gap: 8px;
}

.navbar-brand { flex-shrink: 0; }
.brand-link {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  font-size: 1rem;
  color: var(--color-text);
  white-space: nowrap;
}
.brand-link:hover { text-decoration: none; }
.brand-logo { width: 28px; height: 28px; border-radius: 6px; }

.navbar-links {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
  flex-wrap: nowrap;
  overflow-x: auto;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 6px 12px;
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  border-radius: 6px;
  white-space: nowrap;
  border: none;
  background: none;
  cursor: pointer;
  transition: all var(--transition);
}
.nav-link:hover {
  color: var(--color-text);
  background: var(--color-bg-secondary);
  text-decoration: none;
}
.nav-icon { padding: 6px 8px; }
.nav-icon svg { display: block; }

.search-hint {
  font-size: 0.75rem;
  color: var(--color-text-tertiary);
}
.search-hint kbd {
  display: inline-block;
  padding: 1px 5px;
  font-size: 0.7rem;
  font-family: var(--font-mono);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  background: var(--color-bg-secondary);
}

.navbar-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: 8px;
  border: none;
  background: none;
  cursor: pointer;
}
.navbar-toggle span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
  transition: var(--transition);
}

/* Theme toggle icons */
.icon-moon { display: none; }
[data-theme="dark"] .icon-sun { display: none; }
[data-theme="dark"] .icon-moon { display: block; }

/* --- Search Modal --- */
.search-modal {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 2000;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(4px);
  padding: 10vh 16px;
}
.search-modal.is-open { display: flex; justify-content: center; align-items: flex-start; }

.search-modal-inner {
  width: 100%;
  max-width: 600px;
  background: var(--color-bg);
  border-radius: 12px;
  border: 1px solid var(--color-border);
  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.2);
  overflow: hidden;
}

.search-input-wrap {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  border-bottom: 1px solid var(--color-border-light);
}
.search-input-wrap svg { flex-shrink: 0; color: var(--color-text-tertiary); }
.search-input-wrap input {
  flex: 1;
  border: none;
  outline: none;
  font-size: 1rem;
  background: transparent;
  color: var(--color-text);
}
.search-input-wrap kbd {
  padding: 2px 6px;
  font-size: 0.7rem;
  font-family: var(--font-mono);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  background: var(--color-bg-secondary);
  color: var(--color-text-tertiary);
}

.search-results {
  max-height: 60vh;
  overflow-y: auto;
  padding: 8px;
}
.search-results:empty::after {
  content: "输入关键词搜索文章...";
  display: block;
  padding: 24px;
  text-align: center;
  color: var(--color-text-tertiary);
}
.search-result-item {
  display: block;
  padding: 10px 12px;
  border-radius: 8px;
  color: var(--color-text);
  transition: background var(--transition);
}
.search-result-item:hover {
  background: var(--color-bg-secondary);
  text-decoration: none;
}
.search-result-item .result-title { font-weight: 600; font-size: 0.95rem; }
.search-result-item .result-desc {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  margin-top: 2px;
}

/* --- Main Container --- */
.main-container {
  margin-top: var(--navbar-height);
  min-height: calc(100vh - var(--navbar-height) - 80px);
}

/* --- Three Column Layout --- */
.three-column-layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr) var(--toc-width);
  max-width: 1400px;
  margin: 0 auto;
  gap: 0;
}

/* --- Sidebar Left --- */
.sidebar-left {
  position: sticky;
  top: var(--navbar-height);
  height: calc(100vh - var(--navbar-height));
  overflow-y: auto;
  padding: 16px 0 16px 16px;
  border-right: 1px solid var(--color-border-light);
  font-size: 0.875rem;
  scrollbar-width: thin;
}

.sidebar-toggle {
  display: none;
  position: fixed;
  bottom: 80px;
  left: 16px;
  z-index: 100;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  box-shadow: 0 2px 8px var(--color-card-shadow);
  cursor: pointer;
  align-items: center;
  justify-content: center;
}

.sidebar-group { margin-bottom: 4px; }

.sidebar-group-title {
  display: flex;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 4px;
  width: 100%;
  padding: 6px 12px;
  border: none;
  background: none;
  color: var(--color-text);
  font-weight: 600;
  font-size: 0.875rem;
  cursor: pointer;
  border-radius: 6px;
  line-height: 1.5;
  transition: background var(--transition);
  text-align: left;
  word-break: break-word;
}
.sidebar-group-title:hover { background: var(--color-bg-secondary); }

.sidebar-arrow {
  transition: transform var(--transition);
  flex-shrink: 0;
}
.sidebar-group.is-expanded .sidebar-arrow { transform: rotate(90deg); }

.sidebar-count {
  margin-left: auto;
  font-size: 0.75rem;
  color: var(--color-text-tertiary);
  background: var(--color-bg-tertiary);
  padding: 0 6px;
  border-radius: 10px;
}

.sidebar-items {
  list-style: none;
  display: none;
  padding-left: 8px;
}
.sidebar-group.is-expanded .sidebar-items { display: block; }

.sidebar-link {
  display: block;
  padding: 4px 12px 4px 24px;
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
  border-radius: 6px;
  line-height: 1.5;
  transition: all var(--transition);
  word-break: break-word;
}
.sidebar-link:hover {
  color: var(--color-text);
  background: var(--color-bg-secondary);
  text-decoration: none;
}
.sidebar-link.is-active {
  color: var(--color-primary);
  background: var(--color-primary-light);
  font-weight: 500;
}

/* --- Content Main --- */
.content-main {
  padding: 24px 40px;
  max-width: var(--content-max-width);
  width: 100%;
  margin: 0 auto;
}

/* --- Sidebar Right (TOC) --- */
.sidebar-right {
  position: sticky;
  top: var(--navbar-height);
  height: calc(100vh - var(--navbar-height));
  overflow-y: auto;
  padding: 16px 16px 16px 0;
  font-size: 0.8125rem;
  scrollbar-width: thin;
}

.toc-container { padding-left: 16px; border-left: 1px solid var(--color-border-light); }
.toc-title {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
}

.toc-nav ul { list-style: none; }
.toc-nav > ul { padding: 0; }
.toc-nav li { margin-bottom: 2px; }
.toc-nav a {
  display: block;
  padding: 3px 8px;
  color: var(--color-text-tertiary);
  border-radius: 4px;
  line-height: 1.4;
  transition: all var(--transition);
}
.toc-nav a:hover {
  color: var(--color-text);
  text-decoration: none;
}
.toc-nav a.is-active {
  color: var(--color-primary);
  font-weight: 500;
}
.toc-nav ul ul { padding-left: 12px; }

/* --- Breadcrumb --- */
.breadcrumb {
  font-size: 0.8125rem;
  color: var(--color-text-tertiary);
  margin-bottom: 16px;
}
.breadcrumb a { color: var(--color-text-secondary); }
.breadcrumb a:hover { color: var(--color-primary); }
.breadcrumb .sep { margin: 0 6px; }

/* --- Post Header --- */
.post-header { margin-bottom: 32px; }
.post-title {
  font-size: 1.75rem;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 12px;
}
.post-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
}
.post-meta span { display: inline-flex; align-items: center; gap: 4px; }
.post-meta svg { opacity: 0.6; }
.post-meta .tag {
  display: inline-flex;
  align-items: center;
  line-height: 1;
}

/* Tags and Categories badges */
.tag, .tag-sm {
  display: inline-block;
  padding: 2px 10px;
  font-size: 0.75rem;
  background: var(--color-tag-bg);
  color: var(--color-tag-text);
  border-radius: 12px;
  transition: opacity var(--transition);
}
.tag:hover, .tag-sm:hover { opacity: 0.8; text-decoration: none; }

.cat-badge {
  display: inline-block;
  padding: 2px 10px;
  font-size: 0.75rem;
  background: var(--color-cat-bg);
  color: var(--color-cat-text);
  border-radius: 12px;
  transition: opacity var(--transition);
}
.cat-badge:hover { opacity: 0.8; text-decoration: none; }

/* --- Post Content (Markdown Body) --- */
.markdown-body { font-size: 1rem; line-height: 1.8; }
.markdown-body h1, .markdown-body h2, .markdown-body h3,
.markdown-body h4, .markdown-body h5, .markdown-body h6 {
  margin-top: 1.5em;
  margin-bottom: 0.5em;
  font-weight: 600;
  line-height: 1.3;
}
.markdown-body h1 { font-size: 1.5rem; }
.markdown-body h2 {
  font-size: 1.375rem;
  padding-bottom: 0.3em;
  border-bottom: 1px solid var(--color-border-light);
}
.markdown-body h3 { font-size: 1.2rem; }
.markdown-body h4 { font-size: 1.05rem; }
.markdown-body h5 { font-size: 0.95rem; }

.markdown-body p { margin-bottom: 1em; }
.markdown-body ul, .markdown-body ol { padding-left: 2em; margin-bottom: 1em; }
.markdown-body li { margin-bottom: 0.25em; }
.markdown-body li > p { margin-bottom: 0.5em; }

.markdown-body blockquote {
  padding: 0.5em 1em;
  margin: 0 0 1em;
  border-left: 4px solid var(--color-primary);
  background: var(--color-bg-secondary);
  color: var(--color-text-secondary);
  border-radius: 0 6px 6px 0;
}

.markdown-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  padding: 0.2em 0.4em;
  background: var(--color-code-bg);
  border-radius: 4px;
}

.markdown-body pre {
  margin-bottom: 1em;
  border-radius: 8px;
  overflow-x: auto;
}
.markdown-body pre code {
  padding: 0;
  background: transparent;
  font-size: 0.85rem;
  line-height: 1.5;
}

.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1em;
  font-size: 0.9rem;
}
.markdown-body th, .markdown-body td {
  padding: 8px 12px;
  border: 1px solid var(--color-border);
  text-align: left;
}
.markdown-body th {
  background: var(--color-bg-secondary);
  font-weight: 600;
}

.markdown-body img {
  border-radius: 8px;
  margin: 0.5em 0;
}

.markdown-body hr {
  border: none;
  border-top: 1px solid var(--color-border-light);
  margin: 2em 0;
}

/* Heading anchor links */
.markdown-body .heading-anchor {
  color: inherit;
  text-decoration: none;
}
.markdown-body .heading-anchor:hover {
  color: var(--color-primary);
  text-decoration: none;
}

/* Footnotes */
.markdown-body .footnotes {
  margin-top: 2em;
  padding-top: 1em;
  border-top: 1px solid var(--color-border-light);
  font-size: 0.875rem;
  color: var(--color-text-secondary);
}
.markdown-body .footnotes ol { padding-left: 1.5em; }
.markdown-body .footnotes li { margin-bottom: 0.5em; }
.markdown-body sup a { color: var(--color-primary); font-weight: 600; }

/* Pygments highlight */
.highlight {
  background: var(--color-code-bg);
  border-radius: 8px;
  padding: 16px;
  overflow-x: auto;
}

/* KaTeX */
.katex-block {
  display: block;
  text-align: center;
  margin: 1em 0;
  overflow-x: auto;
}
.katex-inline { /* inline math, no special block styling needed */ }

/* --- Post Footer --- */
.post-footer { margin-top: 48px; }

.edit-link {
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  margin-bottom: 16px;
}
.edit-link a {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  color: var(--color-text-secondary);
}

.post-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  padding: 24px 0;
  border-top: 1px solid var(--color-border-light);
}
.post-nav-item {
  display: flex;
  flex-direction: column;
  padding: 12px 16px;
  border: 1px solid var(--color-border-light);
  border-radius: 8px;
  transition: all var(--transition);
}
.post-nav-item:hover {
  border-color: var(--color-primary);
  text-decoration: none;
}
.post-nav-next { text-align: right; }
.post-nav-empty {
  border: none;
  padding: 0;
}
.nav-label {
  font-size: 0.75rem;
  color: var(--color-text-tertiary);
  margin-bottom: 4px;
}
.nav-title {
  font-size: 0.875rem;
  color: var(--color-text);
  font-weight: 500;
}

.comments-section { margin-top: 32px; padding-top: 24px; border-top: 1px solid var(--color-border-light); }

/* --- Home Page Layout --- */
.home-layout {
  max-width: 1100px;
  margin: 0 auto;
  padding: 32px 24px;
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 40px;
  align-items: start;
}

.home-sidebar {
  position: sticky;
  top: calc(var(--navbar-height) + 32px);
}

.author-card {
  text-align: center;
  padding: 24px 16px;
  background: var(--color-bg-secondary);
  border-radius: 12px;
  border: 1px solid var(--color-border-light);
}

.author-avatar {
  width: 96px;
  height: auto;
  border-radius: 8px;
  margin-bottom: 12px;
}

.author-name {
  font-size: 1.125rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.author-bio {
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
  margin-bottom: 16px;
}

.author-social {
  display: flex;
  justify-content: center;
  gap: 12px;
}
.author-social a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--color-bg-tertiary);
  color: var(--color-text-secondary);
  transition: all var(--transition);
}
.author-social a:hover {
  background: var(--color-primary);
  color: #fff;
  text-decoration: none;
}

.home-main { min-width: 0; }

/* Author Stats */
.author-stats {
  display: flex;
  justify-content: center;
  gap: 4px;
  margin-bottom: 16px;
}
.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 4px 12px;
  color: var(--color-text);
  border-radius: 6px;
  transition: background var(--transition);
}
.stat-item:hover {
  background: var(--color-bg-tertiary);
  text-decoration: none;
}
.stat-num {
  font-size: 1.125rem;
  font-weight: 700;
}
.stat-label {
  font-size: 0.75rem;
  color: var(--color-text-secondary);
}

/* Star Posts */
.star-posts {
  margin-top: 16px;
  padding: 16px;
  background: var(--color-bg-secondary);
  border-radius: 12px;
  border: 1px solid var(--color-border-light);
}
.star-posts-title {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--color-text);
}
.star-posts-title svg {
  color: #f59e0b;
}
.star-posts-list {
  list-style: none;
  padding: 0;
}
.star-posts-list li {
  margin-bottom: 6px;
}
.star-posts-list a {
  display: block;
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
  padding: 4px 0;
  transition: color var(--transition);
}
.star-posts-list a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

/* --- Post Card --- */
.post-card {
  padding: 20px 24px;
  margin-bottom: 12px;
  background: var(--color-bg-secondary);
  border: 1px solid var(--color-border-light);
  border-radius: 12px;
  transition: border-color var(--transition);
}
.post-card:hover {
  border-color: var(--color-border);
}
.post-card:first-child { padding-top: 20px; }

.post-card-title {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 6px;
}
.post-card-title a { color: var(--color-text); }
.post-card-title a:hover { color: var(--color-primary); text-decoration: none; }

.post-card-desc {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.post-card-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 0.8125rem;
  color: var(--color-text-tertiary);
}
.post-card-meta a { color: var(--color-text-tertiary); }
.post-card-meta a:hover { color: var(--color-primary); }
.post-card-cats,
.post-card-tags {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}
.post-card-cats svg,
.post-card-tags svg {
  flex-shrink: 0;
}
.post-card-meta .cat-badge,
.post-card-meta .tag-sm {
  font-size: 0.7rem;
  padding: 1px 8px;
}

.post-card-compact { padding: 16px 20px; }
.post-card-compact .post-card-title { font-size: 1rem; }

/* --- Pagination --- */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-top: 32px;
  padding-top: 24px;
  border-top: 1px solid var(--color-border-light);
}
.page-link {
  padding: 8px 16px;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  font-size: 0.875rem;
  color: var(--color-text);
  transition: all var(--transition);
}
.page-link:hover { border-color: var(--color-primary); text-decoration: none; }
.page-link.disabled {
  color: var(--color-text-tertiary);
  pointer-events: none;
  opacity: 0.5;
}
.page-info { font-size: 0.875rem; color: var(--color-text-secondary); }

/* --- Taxonomy --- */
.taxonomy-content {
  padding: 0;
}
.page-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 24px;
}
.taxonomy-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--color-border-light);
}
.taxonomy-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  background: var(--color-bg-secondary);
  border: 1px solid var(--color-border-light);
  border-radius: 20px;
  font-size: 0.875rem;
  color: var(--color-text);
  transition: all var(--transition);
}
.taxonomy-badge:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  text-decoration: none;
}
.taxonomy-badge.is-active {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}
.taxonomy-badge.is-active .count { color: rgba(255,255,255,0.8); }
.taxonomy-badge .count {
  font-size: 0.75rem;
  color: var(--color-text-tertiary);
}
.taxonomy-hint {
  color: var(--color-text-tertiary);
  font-size: 0.875rem;
}

/* --- Directory Index --- */
.directory-container {
  max-width: 800px;
  margin: 0 auto;
  padding: 32px 24px;
}

/* --- Archive --- */
.archive-container {
  padding: 0;
}
.archive-count {
  font-size: 0.875rem;
  font-weight: 400;
  color: var(--color-text-secondary);
}
.archive-year { margin-bottom: 32px; }
.year-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border-light);
}
.archive-list { list-style: none; }
.archive-item {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding: 6px 0;
}
.archive-item time {
  flex-shrink: 0;
  width: 50px;
  font-size: 0.8125rem;
  color: var(--color-text-tertiary);
  font-family: var(--font-mono);
}
.archive-item a {
  font-size: 0.9375rem;
  color: var(--color-text);
}
.archive-item a:hover { color: var(--color-primary); }

/* --- Page --- */
.page-container {
  max-width: 800px;
  margin: 0 auto;
  padding: 32px 24px;
}
.page-toc {
  margin-bottom: 24px;
  padding: 12px 16px;
  background: var(--color-bg-secondary);
  border-radius: 8px;
}
.page-toc summary {
  font-weight: 600;
  font-size: 0.875rem;
  cursor: pointer;
  color: var(--color-text-secondary);
}

/* --- Footer --- */
.site-footer {
  border-top: 1px solid var(--color-border-light);
  padding: 24px;
  text-align: center;
  font-size: 0.8125rem;
  color: var(--color-text-tertiary);
}
.site-footer a { color: var(--color-text-secondary); }
.busuanzi-stats { margin-top: 4px; font-size: 0.75rem; }

/* --- Back to Top --- */
.back-to-top {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  box-shadow: 0 2px 8px var(--color-card-shadow);
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
  z-index: 100;
}
.back-to-top:hover { border-color: var(--color-primary); }
.back-to-top.is-visible { display: flex; }

/* ========================================
   Responsive Design
   ======================================== */

/* Tablet: hide TOC */
@media (max-width: 1200px) {
  .three-column-layout {
    grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  }
  .sidebar-right { display: none; }
}

/* Mobile */
@media (max-width: 768px) {
  .three-column-layout {
    grid-template-columns: 1fr;
  }

  .sidebar-left {
    position: fixed;
    top: var(--navbar-height);
    left: 0;
    bottom: 0;
    width: 280px;
    background: var(--color-bg);
    border-right: 1px solid var(--color-border);
    transform: translateX(-100%);
    transition: transform 0.3s ease;
    z-index: 500;
    padding: 16px;
  }
  .sidebar-left.is-open { transform: translateX(0); }

  .sidebar-toggle { display: flex; }

  .content-main {
    padding: 16px;
    max-width: 100%;
    overflow-x: hidden;
  }

  .markdown-body pre,
  .markdown-body table {
    max-width: calc(100vw - 32px);
  }

  .katex-block {
    max-width: calc(100vw - 32px);
  }

  .post-meta {
    flex-wrap: wrap;
  }

  .navbar-toggle { display: flex; }
  .navbar-links {
    display: none;
    position: absolute;
    top: var(--navbar-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: 8px;
  }
  .navbar-links.is-open { display: flex; }
  .nav-link { justify-content: flex-start; }
  .search-hint { display: none; }

  .post-nav { grid-template-columns: 1fr; }
  .post-title { font-size: 1.375rem; }

  /* Home layout: stack vertically on mobile */
  .home-layout {
    grid-template-columns: 1fr;
    gap: 0;
    padding: 16px;
  }
  .home-sidebar {
    display: none;
  }

  .post-card {
    padding: 16px;
    margin-bottom: 8px;
    border-radius: 8px;
  }
  .post-card-title { font-size: 1.05rem; }
  .post-card-desc { font-size: 0.8125rem; }
  .post-card-meta { font-size: 0.75rem; }

  .pagination { gap: 8px; margin-top: 24px; padding-top: 16px; }
  .page-link { padding: 6px 12px; font-size: 0.8125rem; }
}