:root {

  --ocean-navy: #0A0E1A;
  --dark-slate: #121826;
  --glacial-blue: #2A3752;
  --iceberg-cyan: #3B82F6;
  --off-white: #E6EAF2;

  --bg-body: var(--ocean-navy);
  --bg-surface: var(--dark-slate);
  --bg-code: #060911;
  --bg-elevated: #161D2E;

  --text-primary: var(--off-white);
  --text-secondary: #94A3B8;
  --text-muted: #64748B;

  --border-cyan: rgba(59, 130, 246, 0.18);
  --border-cyan-strong: rgba(59, 130, 246, 0.45);
  --glass-fill: rgba(230, 234, 242, 0.04);
  --glass-fill-hover: rgba(59, 130, 246, 0.07);

  --difficulty-easy: #4FA37B;
  --difficulty-medium: #C9962F;
  --difficulty-hard: #B4483A;
  --difficulty-insane: #7A4FB5;

  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', Consolas, monospace;

  --header-h: 60px;
  --sidebar-w: 280px;
  --radius: 4px;
  --radius-sm: 3px;
  --transition: 0.2s ease-out;

  --shadow-soft: 0 4px 20px rgba(0, 0, 0, 0.45);
}

[data-theme="light"] {
  --bg-body: #EEF2F8;
  --bg-surface: #FFFFFF;
  --bg-code: #0A0E1A;
  --bg-elevated: #F5F8FC;

  --text-primary: #0F1729;
  --text-secondary: #3D4A63;
  --text-muted: #64748B;

  --glass-fill: rgba(10, 14, 26, 0.03);
  --glass-fill-hover: rgba(59, 130, 246, 0.08);
  --border-cyan: rgba(42, 55, 82, 0.22);
  --border-cyan-strong: rgba(42, 55, 82, 0.45);

  --shadow-soft: 0 4px 20px rgba(15, 23, 41, 0.08);
}

*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg-body);
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 15px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  transition: background var(--transition), color var(--transition);
}

.mono { font-family: var(--font-mono); }

a { color: inherit; text-decoration: none; }

button { font-family: inherit; cursor: pointer; }

h1, h2, h3, h4 { font-weight: 700; line-height: 1.25; margin: 0 0 0.5em; letter-spacing: -0.01em; }
h1 { font-size: 2rem; }
h2 { font-size: 1.4rem; }
h3 { font-size: 1.15rem; }
h4 { font-size: 1rem; }

p { margin: 0 0 1em; color: var(--text-secondary); }

::selection { background: var(--iceberg-cyan); color: var(--ocean-navy); }

a:focus-visible,
button:focus-visible,
input:focus-visible,
[tabindex]:focus-visible {
  outline: 2px solid var(--iceberg-cyan);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--iceberg-cyan);
  color: var(--ocean-navy);
  padding: 10px 16px;
  z-index: 1000;
  font-family: var(--font-mono);
  font-weight: 600;
}
.skip-link:focus { left: 8px; top: 8px; }

.glass {
  background: linear-gradient(var(--glass-fill), var(--glass-fill));
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(11, 19, 43, 0.82);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-cyan);
}
[data-theme="light"] .site-header { background: rgba(255, 255, 255, 0.82); }

.scroll-progress {
  position: sticky;
  top: var(--header-h);
  z-index: 99;
  height: 2px;
  background: transparent;
}
.scroll-progress-fill {
  height: 100%;
  width: 0%;
  background: var(--iceberg-cyan);
  transition: width 0.1s linear;
}

.header-inner {
  height: 100%;
  max-width: 1440px;
  margin: 0 auto;
  padding: 0 20px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 24px;
}

.header-left { display: flex; align-items: center; gap: 12px; justify-self: start; min-width: 0; }

.brand { display: flex; align-items: center; gap: 10px; }
.brand-icon { width: 28px; height: 28px; flex-shrink: 0; object-fit: contain; }
.brand-text { font-family: var(--font-mono); font-weight: 700; font-size: 0.95rem; letter-spacing: 0.02em; color: var(--text-primary); }
.brand-text-accent { color: var(--iceberg-cyan); }

.main-nav { display: flex; gap: 4px; justify-self: center; }
.nav-link {
  padding: 8px 14px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: var(--radius);
  transition: color var(--transition), background var(--transition);
}
.nav-link:hover { color: var(--text-primary); background: var(--glass-fill-hover); }
.nav-link.active { color: var(--iceberg-cyan); background: var(--glass-fill-hover); }

.header-right { display: flex; align-items: center; gap: 10px; justify-self: end; }

.search-box {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--glass-fill);
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
  padding: 6px 10px;
  width: 260px;
  transition: border-color var(--transition);
}
.search-box:focus-within { border-color: var(--border-cyan-strong); }
.search-icon { width: 16px; height: 16px; color: var(--text-muted); flex-shrink: 0; }
.search-box input {
  background: transparent;
  border: none;
  outline: none;
  color: var(--text-primary);
  font-size: 0.85rem;
  width: 100%;
  font-family: var(--font-body);
}
.search-box input::placeholder { color: var(--text-muted); }
.search-kbd {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--text-muted);
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius-sm);
  padding: 1px 6px;
}

.icon-btn {
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-secondary);
  width: 34px;
  height: 34px;
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
}
.icon-btn:hover { color: var(--iceberg-cyan); border-color: var(--border-cyan); background: var(--glass-fill-hover); }
.icon-btn svg { width: 18px; height: 18px; }

.hamburger {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: 8px;
}
.hamburger span { width: 18px; height: 2px; background: currentColor; border-radius: 1px; transition: all var(--transition); }

.search-overlay {
  position: fixed;
  inset: var(--header-h) 0 0 0;
  background: rgba(5, 10, 20, 0.6);
  z-index: 90;
  display: flex;
  justify-content: center;
  padding-top: 60px;
}

.search-overlay[hidden] {
  display: none;
}
.search-results {
  width: min(600px, 90vw);
  max-height: 60vh;
  overflow-y: auto;
  background: var(--bg-surface);
  border: 1px solid var(--border-cyan-strong);
  border-radius: var(--radius);
  box-shadow: var(--shadow-soft);
}
.search-result-item {
  display: block;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-cyan);
  transition: background var(--transition);
}
.search-result-item:last-child { border-bottom: none; }
.search-result-item:hover, .search-result-item:focus-visible { background: var(--glass-fill-hover); }
.search-result-item .sr-type { font-family: var(--font-mono); font-size: 0.68rem; color: var(--iceberg-cyan); text-transform: uppercase; }
.search-result-item .sr-title { font-weight: 600; margin-top: 2px; }
.search-empty { padding: 20px 16px; color: var(--text-muted); font-family: var(--font-mono); font-size: 0.85rem; }

.app-shell {
  display: flex;
  max-width: 1440px;
  margin: 0 auto;
  min-height: calc(100vh - var(--header-h));
}

.sidebar {
  width: var(--sidebar-w);
  flex-shrink: 0;
  border-right: 1px solid var(--border-cyan);
  position: sticky;
  top: var(--header-h);
  align-self: flex-start;
  height: calc(100vh - var(--header-h));
  overflow-y: auto;
}
.sidebar-inner { padding: 20px 14px; }
.sidebar-backdrop { display: none; }

.sidebar-empty { color: var(--text-muted); font-size: 0.85rem; padding: 10px 6px; }

.sidebar-heading {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  text-transform: uppercase;
  padding: 6px 10px;
  margin-top: 10px;
}
.sidebar-heading:first-child { margin-top: 0; }

.sidebar-link {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 10px;
  font-size: 0.85rem;
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  border-left: 2px solid transparent;
  transition: all var(--transition);
}
.sidebar-link:hover { color: var(--text-primary); background: var(--glass-fill-hover); }
.sidebar-link.active { color: var(--iceberg-cyan); border-left-color: var(--iceberg-cyan); background: var(--glass-fill-hover); }
.sidebar-link .sb-dot { width: 6px; height: 6px; border-radius: 50%; border: 1px solid var(--text-muted); flex-shrink: 0; }

.tree-section { margin-bottom: 4px; }
.tree-section-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: transparent;
  border: none;
  color: var(--text-primary);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 10px;
  border-radius: var(--radius-sm);
  transition: background var(--transition);
}
.tree-section-btn:hover { background: var(--glass-fill-hover); }
.tree-section-btn .chev { transition: transform var(--transition); color: var(--text-muted); }
.tree-section-btn[aria-expanded="true"] .chev { transform: rotate(90deg); }
.tree-units { padding-left: 14px; border-left: 1px solid var(--border-cyan); margin-left: 14px; }
.tree-units[hidden] { display: none; }

.chip-list { display: flex; flex-wrap: wrap; gap: 6px; padding: 4px 6px; }
.chip {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  padding: 5px 10px;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  background: transparent;
  transition: all var(--transition);
}
.chip:hover { border-color: var(--border-cyan-strong); color: var(--text-primary); }
.chip.active { background: rgba(59, 130, 246, 0.12); color: var(--iceberg-cyan); border-color: var(--border-cyan-strong); }

.main-content { flex: 1; min-width: 0; padding: 24px 32px 80px; }

.breadcrumbs {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 20px;
  flex-wrap: wrap;
}
.breadcrumbs a { color: var(--text-secondary); transition: color var(--transition); }
.breadcrumbs a:hover { color: var(--iceberg-cyan); }
.breadcrumbs .crumb-sep { color: var(--glacial-blue); }
.breadcrumbs .crumb-current { color: var(--iceberg-cyan); }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 9px 18px;
  font-size: 0.85rem;
  font-weight: 600;
  border-radius: var(--radius);
  border: 1px solid transparent;
  transition: all var(--transition);
  font-family: var(--font-body);
}
.btn-primary { background: var(--iceberg-cyan); color: var(--ocean-navy); }
.btn-primary:hover { background: #60A5FA; }
.btn-primary:disabled { background: var(--glacial-blue); color: var(--text-muted); cursor: not-allowed; }

.btn-ghost { background: transparent; border-color: var(--border-cyan); color: var(--text-secondary); }
.btn-ghost:hover:not(:disabled) { border-color: var(--border-cyan-strong); color: var(--text-primary); }
.btn-ghost:disabled { opacity: 0.4; cursor: not-allowed; }

.text-link { color: var(--iceberg-cyan); font-size: 0.78rem; transition: opacity var(--transition); }
.text-link:hover { opacity: 0.75; }

.hero-panel {
  padding: 32px 0 28px;
  border-bottom: 1px solid var(--border-cyan);
  margin-bottom: 32px;
}
.eyebrow {
  font-size: 0.75rem;
  color: var(--iceberg-cyan);
  letter-spacing: 0.06em;
  margin-bottom: 10px;
}
.hero-sub { max-width: 560px; font-size: 0.95rem; }

.section-block { margin-bottom: 40px; }
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 16px;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
}
.card-grid--list { grid-template-columns: 1fr; }

.card {
  padding: 18px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  border-top: 2px solid transparent;
  transition: border-color var(--transition), transform var(--transition), background var(--transition);
}
.card:hover {
  border-color: var(--border-cyan-strong);
  border-top-color: var(--card-tier-color, var(--border-cyan-strong));
  background: var(--glass-fill-hover);
  transform: translateY(-2px);
}
.card:has(.badge-easy) { --card-tier-color: var(--difficulty-easy); }
.card:has(.badge-medium) { --card-tier-color: var(--difficulty-medium); }
.card:has(.badge-hard) { --card-tier-color: var(--difficulty-hard); }
.card:has(.badge-insane) { --card-tier-color: var(--difficulty-insane); }

.card-top { display: flex; align-items: center; justify-content: space-between; gap: 8px; }

.badge {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  text-transform: uppercase;
  border: 1px solid currentColor;
}
.badge-easy { color: var(--difficulty-easy); }
.badge-medium { color: var(--difficulty-medium); }
.badge-hard { color: var(--difficulty-hard); }
.badge-insane { color: var(--difficulty-insane); }

.card-type { font-family: var(--font-mono); font-size: 0.68rem; color: var(--text-muted); text-transform: uppercase; }

.card h3 { font-size: 1rem; margin: 0; }
.card-desc { font-size: 0.82rem; color: var(--text-secondary); margin: 0; flex: 1; }

.card-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.tag {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  color: var(--text-muted);
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius-sm);
  padding: 2px 7px;
}

.card-cta-row { display: flex; justify-content: flex-end; }

.card-meta-row { display: flex; align-items: center; gap: 10px; font-family: var(--font-mono); font-size: 0.7rem; color: var(--text-muted); }

.card-stats-row {
  display: flex;
  align-items: center;
  gap: 14px;
  font-size: 0.7rem;
  color: var(--text-muted);
}
.card-stats-row .view-count svg { width: 12px; height: 12px; }
.card-stats-row .like-btn { padding: 3px 8px; font-size: 0.68rem; gap: 5px; }
.card-stats-row .like-btn svg { width: 12px; height: 12px; }

.card-quickstart-btn {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--text-secondary);
  background: transparent;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius-sm);
  padding: 3px 9px;
  transition: all var(--transition);
}
.card:hover .card-quickstart-btn { color: var(--iceberg-cyan); border-color: var(--border-cyan-strong); background: rgba(59, 130, 246, 0.1); }
.card-quickstart-btn:hover { background: rgba(59, 130, 246, 0.2); }

.catalog-head { padding: 20px 0 10px; }
.catalog-sub { color: var(--text-secondary); max-width: 620px; }
.filter-bar { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 22px; }

.module-pagenav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--border-cyan);
  flex-wrap: wrap;
}

.lesson-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  max-width: 780px;
  margin: 0 auto 18px;
  font-size: 0.76rem;
  color: var(--text-muted);
}
.lesson-meta .lesson-progress {
  color: var(--iceberg-cyan);
  font-weight: 600;
  letter-spacing: 0.02em;
}

.markdown-body { max-width: 780px; margin: 0 auto; }
.markdown-body--article { max-width: 720px; }

.markdown-body h1 { font-size: 1.8rem; margin-top: 0; }
.markdown-body h2 { margin-top: 2.2em; padding-bottom: 0.4em; border-bottom: 1px solid var(--border-cyan); }
.markdown-body h3 { margin-top: 1.8em; color: var(--iceberg-cyan); }
.markdown-body h4 { margin-top: 1.5em; font-size: 1.05rem; }
.markdown-body h5 { margin-top: 1.3em; font-size: 0.92rem; text-transform: uppercase; letter-spacing: 0.03em; color: var(--text-secondary); }
.markdown-body h6 { margin-top: 1.2em; font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.03em; color: var(--text-muted); }
.markdown-body p { color: var(--text-primary); opacity: 0.92; }
.markdown-body strong { color: var(--text-primary); }
.markdown-body del { color: var(--text-muted); }
.markdown-body a { color: var(--iceberg-cyan); border-bottom: 1px solid var(--border-cyan-strong); }
.markdown-body a:hover { opacity: 0.8; }

.markdown-body ul, .markdown-body ol { padding-left: 1.4em; color: var(--text-primary); }
.markdown-body li { margin-bottom: 0.35em; }
.markdown-body li > p { margin: 0.3em 0; }
.markdown-body ul ul, .markdown-body ul ol,
.markdown-body ol ul, .markdown-body ol ol { margin-top: 0.35em; }

.markdown-body blockquote {
  margin: 1.2em 0;
  padding: 10px 16px;
  border-left: 3px solid var(--iceberg-cyan);
  background: var(--glass-fill);
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--text-secondary);
}
.markdown-body blockquote p:last-child { margin-bottom: 0; }
.markdown-body blockquote blockquote {
  margin: 0.8em 0 0;
  border-left-color: var(--border-cyan-strong);
  background: transparent;
}

.markdown-body code:not(pre code) {
  font-family: var(--font-mono);
  background: var(--glass-fill);
  border: 1px solid var(--border-cyan);
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  font-size: 0.85em;
  color: var(--iceberg-cyan);
}

.code-block {
  position: relative;
  margin: 1.4em 0;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--bg-code);
}
.code-block-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 12px;
  background: rgba(59, 130, 246, 0.05);
  border-bottom: 1px solid var(--border-cyan);
}
.code-block-lang {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.copy-btn {
  display: flex;
  align-items: center;
  gap: 5px;
  background: transparent;
  border: 1px solid var(--border-cyan);
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 0.68rem;
  padding: 4px 9px;
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}
.copy-btn:hover { border-color: var(--border-cyan-strong); color: var(--iceberg-cyan); }
.copy-btn.copied { color: var(--difficulty-easy); border-color: var(--difficulty-easy); }
.copy-btn svg { width: 12px; height: 12px; }

.code-block pre {
  margin: 0;
  padding: 14px 16px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.83rem;
  line-height: 1.65;
  color: var(--off-white);
}
.code-block code { font-family: var(--font-mono); background: none; border: none; padding: 0; color: inherit; }

.tok-kw { color: #C792EA; }
.tok-str { color: #C3E88D; }
.tok-com { color: #6B7893; font-style: italic; }
.tok-fn { color: #82AAFF; }
.tok-num { color: #F78C6C; }
.tok-flag { color: var(--iceberg-cyan); }
.tok-var { color: #FFCB6B; }

.table-scroll {
  overflow-x: auto;
  margin: 1.4em 0;
  -webkit-overflow-scrolling: touch;
}
.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 0;
  font-size: 0.88rem;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
  overflow: hidden;
}
@media (max-width: 560px) {
  .table-scroll table { min-width: 480px; }
}
.markdown-body th {
  background: var(--glass-fill);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--iceberg-cyan);
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border-cyan);
}
.markdown-body td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--border-cyan);
  color: var(--text-secondary);
}
.markdown-body tr:last-child td { border-bottom: none; }

.md-checklist { list-style: none; padding-left: 0; }
.md-checklist li { display: flex; align-items: flex-start; gap: 8px; }
.md-checklist input[type="checkbox"] { margin-top: 4px; accent-color: var(--iceberg-cyan); }
.md-checklist li.checked span { color: var(--text-muted); text-decoration: line-through; }

.task-list-item { list-style: none; margin-left: -1.4em; display: flex; align-items: flex-start; gap: 8px; }
.task-list-item input[type="checkbox"] { margin-top: 4px; accent-color: var(--iceberg-cyan); }
.task-list-item.checked span { color: var(--text-muted); text-decoration: line-through; }

.markdown-body hr { border: none; border-top: 1px solid var(--border-cyan); margin: 2em 0; }
.markdown-body img { max-width: 100%; border-radius: var(--radius); border: 1px solid var(--border-cyan); }

.article-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  padding-bottom: 18px;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--border-cyan);
}
.article-meta strong { color: var(--iceberg-cyan); }

.reading-time { display: inline-flex; align-items: center; gap: 6px; }

.like-btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  background: transparent;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
  padding: 5px 12px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}
.like-btn svg { width: 14px; height: 14px; }
.like-btn:hover:not(:disabled) { border-color: var(--border-cyan-strong); color: var(--iceberg-cyan); }
.like-btn.liked { color: var(--iceberg-cyan); border-color: var(--border-cyan-strong); background: rgba(59, 130, 246, 0.12); }
.like-btn.liked svg { fill: var(--iceberg-cyan); }
.like-btn:disabled { cursor: default; }

.share-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  cursor: pointer;
  padding: 0;
}
.share-btn svg { width: 13px; height: 13px; }
.share-btn:hover { color: var(--iceberg-cyan); }
.share-btn.copied { color: var(--iceberg-cyan); }

.content-layout {
  display: flex;
  align-items: flex-start;
  gap: 48px;
  max-width: 980px;
  margin: 0 auto;
}
.content-layout .markdown-body { flex: 1; min-width: 0; margin: 0; }

.toc-panel {
  width: 200px;
  flex-shrink: 0;
  position: sticky;
  top: calc(var(--header-h) + 24px);
  max-height: calc(100vh - var(--header-h) - 48px);
  display: flex;
  flex-direction: column;
}
.toc-panel-head { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin-bottom: 10px; flex-shrink: 0; }
.toc-heading {
  font-size: 0.68rem;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 0;
}
.toc-bookmark-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  flex-shrink: 0;
  background: transparent;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
}
.toc-bookmark-btn svg { width: 12px; height: 12px; }
.toc-bookmark-btn:hover { color: var(--iceberg-cyan); border-color: var(--border-cyan-strong); }
.toc-bookmark-btn.saved { color: var(--iceberg-cyan); border-color: var(--border-cyan-strong); background: rgba(59, 130, 246, 0.12); }
.toc-bookmark-btn.saved svg { fill: var(--iceberg-cyan); }
.toc-nav { display: flex; flex-direction: column; overflow-y: auto; min-height: 0; }
.toc-link {
  display: block;
  padding: 5px 0 5px 12px;
  border-left: 2px solid var(--border-cyan);
  color: var(--text-secondary);
  font-size: 0.82rem;
  line-height: 1.35;
  text-decoration: none;
  transition: all var(--transition);
}
.toc-link:hover { color: var(--text-primary); }
.toc-link.active { color: var(--iceberg-cyan); border-left-color: var(--iceberg-cyan); }
.toc-link.toc-level-3 { padding-left: 24px; font-size: 0.78rem; }
.toc-link.toc-level-4 { padding-left: 36px; font-size: 0.76rem; opacity: 0.85; }

@media (max-width: 1180px) {
  .toc-panel { display: none; }
}

.md-heading-anchor {
  opacity: 0;
  margin-left: 8px;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.8em;
  transition: opacity var(--transition);
}
.markdown-body h1:hover .md-heading-anchor,
.markdown-body h2:hover .md-heading-anchor,
.markdown-body h3:hover .md-heading-anchor,
.markdown-body h4:hover .md-heading-anchor { opacity: 1; }

.back-to-top {
  position: fixed;
  right: 28px;
  bottom: 28px;
  z-index: 90;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--border-cyan-strong);
  background: var(--bg-surface);
  color: var(--iceberg-cyan);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
  opacity: 0;
  transform: translateY(8px);
  transition: opacity var(--transition), transform var(--transition), border-color var(--transition);
}
.back-to-top.show { opacity: 1; transform: translateY(0); }
.back-to-top:hover { border-color: var(--iceberg-cyan); }
.back-to-top svg { width: 18px; height: 18px; }

@media (max-width: 640px) {
  .back-to-top { right: 16px; bottom: 16px; width: 38px; height: 38px; }
}

.view-404 { padding: 60px 0; max-width: 480px; }
.view-404 h1 { margin-bottom: 12px; }
.view-404 p { margin-bottom: 24px; }

@media (max-width: 960px) {
  .search-box { width: 190px; }
  .sidebar-w-fix { --sidebar-w: 240px; }
}

@media (max-width: 860px) {
  .main-nav { display: none; }
  .hamburger { display: flex; }

  .sidebar {
    position: fixed;
    top: var(--header-h);
    left: 0;
    height: calc(100vh - var(--header-h));
    z-index: 95;
    background: var(--bg-body);
    transform: translateX(-100%);
    transition: transform var(--transition);
    box-shadow: var(--shadow-soft);
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: var(--header-h) 0 0 0;
    background: rgba(0,0,0,0.5);
    z-index: 94;
  }
  .sidebar-backdrop.show { display: block; }

  .main-content { padding: 18px 16px 60px; }
  .search-box { display: none; }
}

@media (max-width: 560px) {
  .header-inner { padding: 0 12px; }
  .brand-text { font-size: 0.8rem; }
  .card-grid { grid-template-columns: 1fr; }
  .module-pagenav { flex-direction: column; align-items: stretch; }
  .module-pagenav .btn { width: 100%; justify-content: center; }

  .hero-panel h1 { font-size: 1.5rem; }
  .hero-sub { font-size: 0.88rem; }
  .lesson-meta { gap: 10px 14px; font-size: 0.72rem; margin-bottom: 14px; }
  .markdown-body h1 { font-size: 1.4rem; }
  .catalog-controls { flex-direction: column; align-items: stretch; }
  .sort-select { width: 100%; }
  .article-meta { gap: 10px; font-size: 0.78rem; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
}

.toast-stack {
  position: fixed;
  right: 20px;
  bottom: 20px;
  z-index: 300;
  display: flex;
  flex-direction: column-reverse;
  gap: 10px;
  pointer-events: none;
}
.toast {
  pointer-events: auto;
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 220px;
  max-width: 340px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-cyan-strong);
  border-left: 3px solid var(--iceberg-cyan);
  border-radius: var(--radius);
  padding: 12px 14px;
  box-shadow: var(--shadow-soft);
  font-size: 0.85rem;
  color: var(--text-primary);
  animation: toast-in 0.22s ease-out;
}
.toast.toast-leaving { animation: toast-out 0.18s ease-in forwards; }
.toast.toast-error { border-left-color: var(--difficulty-hard); }
.toast.toast-success { border-left-color: var(--difficulty-easy); }
@keyframes toast-in { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
@keyframes toast-out { from { opacity: 1; } to { opacity: 0; transform: translateX(12px); } }

@media (max-width: 560px) {
  .toast-stack { left: 12px; right: 12px; bottom: 12px; }
  .toast { max-width: none; }
}

.bookmark-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: transparent;
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
  padding: 5px 10px;
  color: var(--text-secondary);
  font-size: 0.78rem;
}
.bookmark-btn svg { width: 13px; height: 13px; }
.bookmark-btn:hover { border-color: var(--border-cyan-strong); color: var(--iceberg-cyan); }
.bookmark-btn.saved { color: var(--iceberg-cyan); border-color: var(--border-cyan-strong); background: rgba(59, 130, 246, 0.12); }
.bookmark-btn.saved svg { fill: var(--iceberg-cyan); }

.view-count { display: inline-flex; align-items: center; gap: 5px; }
.view-count svg { width: 13px; height: 13px; opacity: 0.75; }

.catalog-controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 4px;
}
.sort-select {
  background: var(--glass-fill);
  border: 1px solid var(--border-cyan);
  border-radius: var(--radius);
  color: var(--text-primary);
  padding: 6px 10px;
  font-family: var(--font-mono);
  font-size: 0.76rem;
  cursor: pointer;
}
.sort-select:focus { outline: none; border-color: var(--border-cyan-strong); }

.related-section { margin-top: 56px; padding-top: 28px; border-top: 1px solid var(--border-cyan); }
.related-heading { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-muted); margin: 0 0 14px; }
.related-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 14px; }

.skeleton-card {
  height: 168px;
  border-radius: var(--radius);
  background: linear-gradient(100deg, var(--glass-fill) 30%, var(--glass-fill-hover) 50%, var(--glass-fill) 70%);
  background-size: 200% 100%;
  animation: skeleton-shimmer 1.3s ease-in-out infinite;
  border: 1px solid var(--border-cyan);
}
@keyframes skeleton-shimmer { from { background-position: 200% 0; } to { background-position: -200% 0; } }

.site-footer {
  max-width: 1180px;
  margin: 40px auto 0;
  padding: 24px 32px 40px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  border-top: 1px solid var(--border-cyan);
  color: var(--text-muted);
  font-size: 0.78rem;
}
.site-footer a { color: var(--text-secondary); }
.site-footer a:hover { color: var(--iceberg-cyan); }
.footer-links { display: flex; gap: 16px; flex-wrap: wrap; }

@media (max-width: 860px) {
  .site-footer { padding: 24px 16px 40px; }
}