/* ============================================================
   Business English Knowledge Base
   Editorial Serif Design System
   ============================================================ */

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --background: #fafaf8;
  --foreground: #1a1a1a;
  --muted: #f5f3f0;
  --muted-foreground: #6b6b6b;
  --accent: #b8860b;
  --accent-secondary: #d4a84b;
  --accent-foreground: #ffffff;
  --border: #e8e4df;
  --card: #ffffff;
  --ring: #b8860b;

  --sidebar-width: 300px;
  --header-height: 88px;

  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-pill: 999px;

  --shadow-sm: 0 1px 2px rgba(26, 26, 26, 0.04);
  --shadow-md: 0 4px 12px rgba(26, 26, 26, 0.06);
  --shadow-lg: 0 8px 24px rgba(26, 26, 26, 0.08);

  --font-display: "Playfair Display", Georgia, serif;
  --font-body: "Source Sans 3", "Segoe UI", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", "Consolas", monospace;

  --transition-fast: 150ms ease-out;
  --transition: 200ms ease-out;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  background: var(--background);
  color: var(--foreground);
  line-height: 1.75;
  letter-spacing: 0.01em;
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image: radial-gradient(rgba(26, 26, 26, 0.03) 0.5px, transparent 0.5px);
  background-size: 3px 3px;
  opacity: 0.3;
  z-index: -2;
}

body::after {
  content: "";
  position: fixed;
  width: min(72vw, 800px);
  height: min(72vw, 800px);
  left: -120px;
  top: -180px;
  pointer-events: none;
  z-index: -1;
  background: radial-gradient(circle, rgba(184, 134, 11, 0.08) 0%, rgba(184, 134, 11, 0.03) 38%, transparent 72%);
  filter: blur(48px);
  opacity: 0.95;
}

.site-header,
.layout,
.sidebar-toggle {
  position: relative;
  z-index: 1;
}

button,
input {
  font: inherit;
}

button {
  cursor: pointer;
  touch-action: manipulation;
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 4px;
}

:focus-visible {
  outline: 2px solid var(--ring);
  outline-offset: 2px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.site-header {
  position: sticky;
  top: 0;
  backdrop-filter: blur(8px);
  background: color-mix(in srgb, var(--background) 92%, white 8%);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  min-height: var(--header-height);
}

.header-inner {
  max-width: 1320px;
  margin: 0 auto;
  min-height: var(--header-height);
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.header-brand {
  border: none;
  background: transparent;
  display: flex;
  align-items: center;
  gap: 14px;
  text-align: left;
  color: inherit;
  padding: 4px 2px;
}

.brand-icon {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--border);
  display: grid;
  place-items: center;
  font-size: 20px;
  background: var(--card);
  box-shadow: var(--shadow-sm);
}

.brand-text h1 {
  font-family: var(--font-display);
  font-size: clamp(1.24rem, 1rem + 0.75vw, 1.75rem);
  line-height: 1.2;
  font-weight: 600;
  letter-spacing: -0.02em;
}

.brand-text p {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--muted-foreground);
  line-height: 1.4;
  margin-top: 3px;
}

.header-search {
  position: relative;
  width: min(540px, 100%);
}

.header-search input {
  width: 100%;
  min-height: 48px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border);
  background: color-mix(in srgb, var(--card) 85%, var(--muted) 15%);
  color: var(--foreground);
  padding: 10px 48px 10px 46px;
  font-size: 0.98rem;
  transition: border-color var(--transition), box-shadow var(--transition), background-color var(--transition);
}

.header-search input::placeholder {
  color: color-mix(in srgb, var(--muted-foreground) 60%, transparent);
}

.header-search input:hover {
  border-color: color-mix(in srgb, var(--accent) 35%, var(--border) 65%);
}

.header-search input:focus {
  border-color: var(--accent);
  background: var(--card);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 24%, transparent);
  outline: none;
}

.search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 14px;
  pointer-events: none;
  opacity: 0.75;
}

.search-clear {
  position: absolute;
  right: 9px;
  top: 50%;
  transform: translateY(-50%);
  width: 32px;
  height: 32px;
  min-height: 32px;
  border: none;
  border-radius: 50%;
  background: transparent;
  color: var(--muted-foreground);
  display: none;
  place-items: center;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.search-clear.visible {
  display: grid;
}

.search-clear:hover {
  color: var(--foreground);
  background: var(--muted);
}

.layout {
  display: grid;
  grid-template-columns: minmax(240px, var(--sidebar-width)) minmax(0, 1fr);
  gap: 28px;
  max-width: 1320px;
  margin: 0 auto;
  padding: 36px 24px 60px;
}

.sidebar {
  position: sticky;
  top: calc(var(--header-height) + 22px);
  align-self: start;
  background: color-mix(in srgb, var(--card) 96%, var(--muted) 4%);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  max-height: calc(100vh - var(--header-height) - 44px);
  overflow-y: auto;
}

.sidebar-inner {
  padding: 20px 16px 18px;
}

.sidebar-section {
  margin-bottom: 18px;
}

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

.sidebar-track-block {
  padding-bottom: 2px;
  border-bottom: 1px solid var(--border);
}

.sidebar-track-group {
  padding-bottom: 10px;
}

.sidebar-track-toggle {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  min-height: 52px;
  padding: 6px 0;
  border: none;
  background: transparent;
  color: var(--foreground);
  text-align: left;
  transition: color var(--transition), opacity var(--transition);
}

.sidebar-track-toggle:hover {
  color: color-mix(in srgb, var(--accent) 82%, var(--foreground) 18%);
}

.sidebar-track-toggle:focus {
  outline: none;
}

.sidebar-track-toggle.active {
  color: color-mix(in srgb, var(--accent) 82%, var(--foreground) 18%);
}

.sidebar-track-heading {
  min-width: 0;
}

.sidebar-label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.sidebar-label::before,
.sidebar-label::after {
  content: "";
  height: 1px;
  background: var(--border);
  flex: 1;
}

.sidebar-track-title {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0;
}

.sidebar-track-subtitle {
  display: block;
  font-size: 0.86rem;
  color: var(--muted-foreground);
  margin-top: 5px;
  margin-bottom: 0;
}

.sidebar-track-meta {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-left: 14px;
}

.sidebar-track-chevron {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--muted-foreground);
  transition: transform var(--transition), color var(--transition);
}

.sidebar-track-toggle.expanded .sidebar-track-chevron {
  color: var(--accent);
  transform: rotate(180deg);
}

.sidebar-track-content {
  padding-top: 8px;
}

.sidebar-track-content[hidden] {
  display: none;
}

.count-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.9em;
  height: 1.9em;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border);
  background: var(--muted);
  color: var(--muted-foreground);
  font-size: 0.73rem;
  font-family: var(--font-mono);
  letter-spacing: 0.05em;
  padding: 0 0.5em;
}

.sidebar-track-toggle.active .count-badge,
.sidebar-track-toggle.expanded .count-badge {
  border-color: color-mix(in srgb, var(--accent) 45%, var(--border) 55%);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 9%, white 91%);
}

.category-list {
  display: grid;
  gap: 6px;
}

.category-item {
  width: 100%;
  min-height: 44px;
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  background: transparent;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 10px;
  text-align: left;
  padding: 8px 10px;
  color: var(--foreground);
  transition: border-color var(--transition), background-color var(--transition), color var(--transition);
}

.category-item:hover {
  border-color: var(--border);
  background: color-mix(in srgb, var(--muted) 76%, var(--card) 24%);
}

.category-item.active {
  border-color: color-mix(in srgb, var(--accent) 50%, var(--border) 50%);
  background: color-mix(in srgb, var(--accent) 8%, var(--card) 92%);
  color: var(--accent);
}

.category-icon {
  width: 22px;
  text-align: center;
  font-size: 0.95rem;
}

.category-name {
  font-size: 0.92rem;
  line-height: 1.35;
}

.category-count {
  font-family: var(--font-mono);
  font-size: 0.67rem;
  letter-spacing: 0.06em;
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  color: var(--muted-foreground);
  background: var(--card);
  padding: 2px 7px;
}

.job-lesson-list {
  display: grid;
  gap: 6px;
}

.job-lesson-item {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--card);
  color: var(--foreground);
  transition: border-color var(--transition), background-color var(--transition), box-shadow var(--transition), color var(--transition);
  overflow: hidden;
}

.job-lesson-item:hover,
.job-lesson-item:focus-within {
  border-color: color-mix(in srgb, var(--accent) 50%, var(--border) 50%);
  background: color-mix(in srgb, var(--accent) 8%, var(--card) 92%);
}

.job-lesson-item.active {
  border-color: color-mix(in srgb, var(--accent) 62%, var(--border) 38%);
  background: color-mix(in srgb, var(--accent) 10%, var(--card) 90%);
  box-shadow: var(--shadow-sm);
}

.job-lesson-item.expanded {
  border-color: color-mix(in srgb, var(--accent) 58%, var(--border) 42%);
  box-shadow: var(--shadow-sm);
}

.job-lesson-toggle {
  width: 100%;
  min-height: 42px;
  border: none;
  background: transparent;
  color: inherit;
  text-align: left;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 10px;
  padding: 8px 10px;
}

.job-lesson-toggle:focus {
  outline: none;
}

.job-lesson-number {
  width: 26px;
  height: 26px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: var(--muted-foreground);
  background: var(--muted);
}

.job-lesson-item.active .job-lesson-number,
.job-lesson-item.expanded .job-lesson-number {
  border-color: color-mix(in srgb, var(--accent) 40%, var(--border) 60%);
  background: color-mix(in srgb, var(--accent) 12%, var(--muted) 88%);
  color: color-mix(in srgb, var(--accent) 85%, var(--foreground) 15%);
}

.job-lesson-title {
  font-size: 0.84rem;
  line-height: 1.35;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.job-lesson-item.expanded .job-lesson-title {
  white-space: normal;
}

.job-lesson-chevron {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--muted-foreground);
  transition: transform var(--transition), color var(--transition);
  transform-origin: center;
}

.job-lesson-item.expanded .job-lesson-chevron {
  color: var(--accent);
  transform: rotate(180deg);
}

.job-lesson-panel {
  display: grid;
  gap: 10px;
  padding: 10px 12px 12px 46px;
  border-top: 1px solid color-mix(in srgb, var(--accent) 12%, var(--border) 88%);
  background: color-mix(in srgb, var(--muted) 54%, var(--card) 46%);
}

.job-lesson-preview-title {
  font-size: 0.78rem;
  font-weight: 600;
  line-height: 1.45;
  color: color-mix(in srgb, var(--accent) 78%, var(--foreground) 22%);
}

.job-lesson-summary {
  font-size: 0.76rem;
  line-height: 1.6;
  color: var(--muted-foreground);
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.job-lesson-source {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--accent);
}

.job-lesson-open {
  justify-self: start;
  min-height: 32px;
  border: 1px solid color-mix(in srgb, var(--accent) 38%, var(--border) 62%);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--accent) 10%, var(--card) 90%);
  color: color-mix(in srgb, var(--accent) 86%, var(--foreground) 14%);
  padding: 6px 12px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  transition: border-color var(--transition-fast), background-color var(--transition-fast), color var(--transition-fast);
}

.job-lesson-open:hover {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 18%, var(--card) 82%);
}

.tag-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tag-btn {
  min-height: 32px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--muted-foreground);
  border-radius: var(--radius-pill);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  padding: 5px 10px;
  transition: border-color var(--transition), background-color var(--transition), color var(--transition), box-shadow var(--transition);
}

.tag-btn:hover {
  border-color: color-mix(in srgb, var(--accent) 50%, var(--border) 50%);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, var(--card) 92%);
}

.tag-btn.active {
  border-color: var(--accent);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 11%, var(--card) 89%);
  box-shadow: var(--shadow-sm);
}

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

.hero-shell {
  position: relative;
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 28px;
  background:
    linear-gradient(135deg, color-mix(in srgb, var(--card) 96%, white 4%), color-mix(in srgb, var(--muted) 88%, white 12%)),
    radial-gradient(circle at top right, color-mix(in srgb, var(--accent) 14%, transparent), transparent 48%);
  box-shadow: var(--shadow-md);
  padding: 34px 34px 28px;
  margin-bottom: 30px;
}

.hero-shell::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(120deg, transparent 0%, transparent 58%, color-mix(in srgb, var(--accent) 8%, transparent) 100%);
  pointer-events: none;
}

.hero-shell::after {
  content: "";
  position: absolute;
  width: 240px;
  height: 240px;
  right: -56px;
  top: -84px;
  border-radius: 50%;
  border: 1px solid color-mix(in srgb, var(--accent) 20%, transparent);
  opacity: 0.65;
  pointer-events: none;
}

.hero-grid,
.hero-stats {
  position: relative;
  z-index: 1;
}

.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(300px, 0.8fr);
  gap: 24px;
  align-items: start;
}

.hero-grid-single {
  grid-template-columns: minmax(0, 1fr);
}

.hero-eyebrow {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 16px;
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(2.7rem, 2rem + 2.2vw, 4.2rem);
  line-height: 1.03;
  font-weight: 600;
  letter-spacing: -0.03em;
  max-width: 10ch;
  margin-bottom: 16px;
}

.hero-lead {
  max-width: 60ch;
  font-size: 1.06rem;
  line-height: 1.8;
  color: color-mix(in srgb, var(--foreground) 88%, var(--muted-foreground) 12%);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 24px;
}

.hero-action {
  min-height: 44px;
  border: 1px solid color-mix(in srgb, var(--accent) 28%, var(--border) 72%);
  border-radius: var(--radius-pill);
  background: var(--card);
  color: var(--foreground);
  padding: 10px 16px;
  transition: border-color var(--transition), background-color var(--transition), color var(--transition), box-shadow var(--transition);
}

.hero-action:hover {
  border-color: color-mix(in srgb, var(--accent) 62%, var(--border) 38%);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, var(--card) 92%);
  box-shadow: var(--shadow-sm);
}

.hero-action-primary {
  background: color-mix(in srgb, var(--foreground) 96%, black 4%);
  color: var(--accent-foreground);
  border-color: color-mix(in srgb, var(--foreground) 96%, black 4%);
}

.hero-action-primary:hover {
  color: var(--accent-foreground);
  background: color-mix(in srgb, var(--foreground) 86%, var(--accent) 14%);
  border-color: color-mix(in srgb, var(--foreground) 86%, var(--accent) 14%);
}

.hero-action-ghost {
  background: transparent;
}

.hero-note {
  max-width: 56ch;
  margin-top: 18px;
  padding-left: 14px;
  border-left: 2px solid color-mix(in srgb, var(--accent) 52%, var(--border) 48%);
  color: var(--muted-foreground);
  font-size: 0.95rem;
  line-height: 1.75;
}

.hero-side {
  display: grid;
  gap: 16px;
}

.hero-track-grid {
  display: grid;
  gap: 14px;
}

.track-spotlight {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 22px;
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--card) 92%, white 8%), color-mix(in srgb, var(--muted) 70%, var(--card) 30%));
  padding: 18px;
  text-align: left;
  box-shadow: var(--shadow-sm);
  transition: border-color var(--transition), transform var(--transition), box-shadow var(--transition), background-color var(--transition);
}

.track-spotlight:hover {
  transform: translateY(-1px);
  border-color: color-mix(in srgb, var(--accent) 52%, var(--border) 48%);
  box-shadow: var(--shadow-md);
}

.track-spotlight-kicker {
  display: inline-flex;
  align-items: center;
  min-height: 26px;
  border: 1px solid color-mix(in srgb, var(--accent) 30%, var(--border) 70%);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--accent) 9%, var(--card) 91%);
  color: var(--accent);
  padding: 4px 10px;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.track-spotlight-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-top: 14px;
}

.track-spotlight-title {
  font-family: var(--font-display);
  font-size: 1.6rem;
  line-height: 1.15;
  margin-bottom: 8px;
}

.track-spotlight-copy {
  color: var(--muted-foreground);
  font-size: 0.93rem;
  line-height: 1.7;
}

.track-spotlight-count {
  flex-shrink: 0;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted-foreground);
}

.track-spotlight-tags,
.card-tags,
.hero-tag-ribbon {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.track-spotlight-tags {
  margin-top: 16px;
}

.track-spotlight-tags span,
.card-tag,
.hero-tag {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--muted) 64%, var(--card) 36%);
  padding: 4px 10px;
  font-family: var(--font-mono);
  font-size: 0.67rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted-foreground);
}

.hero-tag-ribbon {
  margin-top: 2px;
}

.hero-tag {
  background: var(--card);
  transition: border-color var(--transition-fast), color var(--transition-fast), background-color var(--transition-fast);
}

.hero-tag:hover {
  border-color: color-mix(in srgb, var(--accent) 54%, var(--border) 46%);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 9%, var(--card) 91%);
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  margin-top: 22px;
}

.hero-stat-card {
  border: 1px solid var(--border);
  border-radius: 18px;
  background: color-mix(in srgb, var(--card) 84%, var(--muted) 16%);
  padding: 16px 18px;
}

.hero-stat-value {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 1.4rem + 0.8vw, 2.35rem);
  line-height: 1;
  letter-spacing: -0.03em;
  color: color-mix(in srgb, var(--accent) 74%, var(--foreground) 26%);
}

.hero-stat-label {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--foreground);
}

.hero-stat-note {
  margin-top: 8px;
  font-size: 0.87rem;
  line-height: 1.65;
  color: var(--muted-foreground);
}

.context-bar {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: color-mix(in srgb, var(--muted) 60%, var(--card) 40%);
  padding: 14px 16px;
  margin-bottom: 24px;
}

.context-copy {
  min-width: 0;
}

.context-label {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 6px;
}

.context-description {
  color: var(--muted-foreground);
  font-size: 0.93rem;
  line-height: 1.65;
}

.context-reset {
  display: none;
  flex-shrink: 0;
  min-height: 38px;
  border: 1px solid color-mix(in srgb, var(--accent) 40%, var(--border) 60%);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--accent) 9%, var(--card) 91%);
  color: color-mix(in srgb, var(--accent) 84%, var(--foreground) 16%);
  padding: 8px 14px;
  font-family: var(--font-mono);
  font-size: 0.69rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.context-reset.visible {
  display: inline-flex;
  align-items: center;
}

.lesson-card {
  display: grid;
  gap: 12px;
  align-content: start;
}

.card-meta-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px 12px;
  font-family: var(--font-mono);
  font-size: 0.67rem;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-transform: uppercase;
}

.card-track {
  color: var(--accent);
}

.card-stats {
  color: var(--muted-foreground);
}

.card-insight-label {
  font-family: var(--font-mono);
  font-size: 0.67rem;
  font-weight: 600;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--accent) 82%, var(--foreground) 18%);
}

.card-insight {
  padding-top: 10px;
  border-top: 1px dashed color-mix(in srgb, var(--border) 80%, var(--accent) 20%);
  color: var(--muted-foreground);
  font-size: 0.88rem;
  line-height: 1.65;
}

.card-footer {
  margin-top: auto;
}

.detail-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  grid-template-areas: "primary rail";
  gap: 22px;
  align-items: start;
}

.detail-primary {
  grid-area: primary;
  min-width: 0;
}

.detail-rail {
  grid-area: rail;
  position: sticky;
  top: calc(var(--header-height) + 22px);
  display: grid;
  gap: 12px;
  align-self: start;
}

.detail-body {
  display: grid;
  gap: 16px;
}

.detail-stat-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  margin-top: 18px;
}

.detail-stat-chip,
.rail-stat {
  border: 1px solid color-mix(in srgb, var(--accent) 14%, var(--border) 86%);
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--muted) 60%, var(--card) 40%);
  padding: 12px;
}

.detail-stat-number,
.rail-stat-value {
  display: block;
  font-family: var(--font-display);
  font-size: 1.42rem;
  line-height: 1;
  color: color-mix(in srgb, var(--accent) 74%, var(--foreground) 26%);
}

.detail-stat-name,
.rail-stat-name {
  display: block;
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: var(--muted-foreground);
}

.rail-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--card);
  box-shadow: var(--shadow-sm);
  padding: 16px;
}

.rail-label,
.detail-footer-label {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
}

.rail-stat-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 12px;
}

.rail-outline,
.rail-link-list,
.rail-related-list {
  display: grid;
  gap: 8px;
  margin-top: 12px;
}

.rail-outline-btn,
.rail-related-card {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: transparent;
  text-align: left;
  transition: border-color var(--transition), background-color var(--transition), box-shadow var(--transition);
}

.rail-outline-btn {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 10px;
  padding: 10px 12px;
}

.rail-outline-btn:hover,
.rail-related-card:hover {
  border-color: color-mix(in srgb, var(--accent) 52%, var(--border) 48%);
  background: color-mix(in srgb, var(--accent) 6%, var(--card) 94%);
  box-shadow: var(--shadow-sm);
}

.rail-outline-index,
.rail-related-num,
.section-index {
  font-family: var(--font-mono);
  font-size: 0.69rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.rail-outline-title,
.rail-related-title {
  display: block;
  font-size: 0.9rem;
  line-height: 1.45;
  color: var(--foreground);
}

.rail-outline-meta,
.rail-related-meta {
  display: block;
  margin-top: 4px;
  font-size: 0.8rem;
  line-height: 1.55;
  color: var(--muted-foreground);
}

.rail-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  min-height: 40px;
  border: 1px solid color-mix(in srgb, var(--accent) 34%, var(--border) 66%);
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--accent) 8%, var(--card) 92%);
  color: color-mix(in srgb, var(--accent) 86%, var(--foreground) 14%);
  padding: 10px 12px;
  font-family: var(--font-mono);
  font-size: 0.69rem;
  font-weight: 600;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

.rail-link:hover {
  text-decoration: none;
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 16%, var(--card) 84%);
}

.rail-related-card {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 10px;
  padding: 10px 12px;
  align-items: start;
}

.detail-footer-nav {
  margin-top: 18px;
}

.detail-footer-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 12px;
}

.detail-jump-card {
  min-height: 126px;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--card);
  box-shadow: var(--shadow-sm);
  padding: 18px;
  text-align: left;
  display: grid;
  gap: 8px;
  transition: border-color var(--transition), background-color var(--transition), box-shadow var(--transition);
}

.detail-jump-card:hover {
  border-color: color-mix(in srgb, var(--accent) 52%, var(--border) 48%);
  background: color-mix(in srgb, var(--accent) 5%, var(--card) 95%);
  box-shadow: var(--shadow-md);
}

.detail-jump-card.is-disabled {
  opacity: 0.6;
  cursor: default;
}

.detail-jump-kicker {
  font-family: var(--font-mono);
  font-size: 0.69rem;
  font-weight: 600;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: var(--accent);
}

.detail-jump-title {
  font-family: var(--font-display);
  font-size: 1.18rem;
  line-height: 1.28;
}

.detail-jump-meta {
  color: var(--muted-foreground);
  font-size: 0.85rem;
  line-height: 1.6;
}

.section-block {
  scroll-margin-top: calc(var(--header-height) + 24px);
}

.section-heading {
  justify-content: flex-start;
  flex-wrap: wrap;
}

.section-heading::before {
  display: none;
}

.section-heading::after {
  min-width: 32px;
}

.section-index {
  min-width: 2.4em;
}

.section-count {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted-foreground);
}

.panel.hidden {
  display: none;
}

.panel {
  animation: fade-in 380ms ease-out;
}

.panel-kicker {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 14px;
}

.panel-kicker .rule {
  height: 1px;
  flex: 1;
  background: var(--border);
}

.kicker-text {
  font-family: var(--font-mono);
  font-size: 0.73rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  white-space: nowrap;
}

.panel-header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px 20px;
  margin-bottom: 4px;
}

.panel-header h2 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 1.4rem + 1.8vw, 2.7rem);
  font-weight: 500;
  line-height: 1.15;
  letter-spacing: -0.015em;
}

.result-count {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted-foreground);
}

.panel-lead {
  color: var(--muted-foreground);
  font-size: 1.03rem;
  max-width: 68ch;
  margin-bottom: 24px;
}

.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 18px;
}

.lesson-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--card);
  text-align: left;
  padding: 18px 18px 16px;
  position: relative;
  transition: border-color var(--transition), background-color var(--transition), box-shadow var(--transition);
  box-shadow: var(--shadow-sm);
  color: inherit;
  width: 100%;
}

.lesson-card::before {
  content: "";
  position: absolute;
  top: -1px;
  left: -1px;
  right: -1px;
  height: 2px;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
  background: linear-gradient(90deg, color-mix(in srgb, var(--accent) 85%, var(--accent-secondary) 15%), color-mix(in srgb, var(--accent-secondary) 75%, white 25%));
  opacity: 0.88;
}

.lesson-card:hover {
  border-color: color-mix(in srgb, var(--accent) 55%, var(--border) 45%);
  background: color-mix(in srgb, var(--card) 86%, var(--muted) 14%);
  box-shadow: var(--shadow-md);
}

.card-number {
  display: flex;
  align-items: baseline;
  gap: 8px;
  margin-bottom: 8px;
}

.card-number-label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--muted-foreground);
}

.card-number-value {
  font-family: var(--font-display);
  font-size: 1.35rem;
  line-height: 1;
  color: color-mix(in srgb, var(--accent) 72%, var(--foreground) 28%);
}

.card-title {
  font-family: var(--font-display);
  font-size: 1.26rem;
  line-height: 1.3;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-bottom: 4px;
}

.card-chinese {
  font-size: 0.95rem;
  color: var(--muted-foreground);
  margin-bottom: 10px;
  line-height: 1.45;
}

.card-summary {
  font-size: 0.96rem;
  color: color-mix(in srgb, var(--muted-foreground) 90%, var(--foreground) 10%);
  margin-bottom: 14px;
  line-height: 1.65;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.card-category {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  background: var(--muted);
  padding: 4px 10px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--muted-foreground) 85%, var(--foreground) 15%);
}

.card-arrow {
  color: var(--accent);
  font-size: 1rem;
  line-height: 1;
}

.no-results {
  grid-column: 1 / -1;
  text-align: center;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--card);
  padding: 72px 24px;
}

.no-results-icon {
  font-size: 2.2rem;
  margin-bottom: 14px;
}

.no-results h3 {
  font-family: var(--font-display);
  font-size: 1.5rem;
  margin-bottom: 6px;
}

.no-results p {
  color: var(--muted-foreground);
  font-size: 1rem;
}

.detail-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px 12px;
  margin-bottom: 18px;
}

.detail-nav-arrows {
  display: flex;
  gap: 8px;
}

.btn-back,
.btn-prev,
.btn-next {
  min-height: 44px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--card);
  color: var(--foreground);
  font-size: 0.95rem;
  line-height: 1.2;
  transition: border-color var(--transition), color var(--transition), background-color var(--transition), box-shadow var(--transition);
  padding: 10px 14px;
}

.btn-prev,
.btn-next {
  color: var(--muted-foreground);
  min-width: 96px;
}

.btn-back:hover,
.btn-prev:hover,
.btn-next:hover {
  border-color: color-mix(in srgb, var(--accent) 56%, var(--border) 44%);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 7%, var(--card) 93%);
}

.btn-prev:disabled,
.btn-next:disabled {
  opacity: 0.42;
  cursor: not-allowed;
}

.detail-header {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  position: relative;
  margin-bottom: 18px;
  padding: 28px 26px;
}

.detail-header::before {
  content: "";
  position: absolute;
  top: -1px;
  left: -1px;
  right: -1px;
  height: 2px;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
  background: linear-gradient(90deg, color-mix(in srgb, var(--accent) 85%, var(--accent-secondary) 15%), color-mix(in srgb, var(--accent-secondary) 72%, white 28%));
}

.detail-lesson-num {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--accent);
  margin-bottom: 8px;
}

.detail-title {
  font-family: var(--font-display);
  font-size: clamp(2.05rem, 1.4rem + 1.55vw, 2.8rem);
  line-height: 1.17;
  font-weight: 500;
  letter-spacing: -0.015em;
  margin-bottom: 6px;
}

.detail-chinese-title {
  color: var(--muted-foreground);
  font-size: 1.06rem;
  line-height: 1.55;
  margin-bottom: 14px;
}

.detail-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 14px;
}

.detail-category,
.detail-tag {
  display: inline-flex;
  align-items: center;
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  min-height: 30px;
  padding: 4px 10px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.detail-category {
  background: color-mix(in srgb, var(--accent) 8%, var(--card) 92%);
  color: var(--accent);
}

.detail-tag {
  background: var(--muted);
  color: var(--muted-foreground);
}

.detail-summary {
  border-left: 2px solid var(--accent);
  background: color-mix(in srgb, var(--muted) 72%, var(--card) 28%);
  border-radius: var(--radius-sm);
  padding: 12px 14px;
  font-size: 1rem;
  color: color-mix(in srgb, var(--foreground) 88%, var(--muted-foreground) 12%);
}

.section-block {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--card);
  box-shadow: var(--shadow-sm);
  margin-bottom: 16px;
  overflow: hidden;
}

.section-heading {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 18px;
  border-bottom: 1px solid var(--border);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  background: color-mix(in srgb, var(--muted) 70%, var(--card) 30%);
}

.section-heading::before,
.section-heading::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--border);
}

.vocab-item {
  padding: 16px 18px;
  border-bottom: 1px solid var(--border);
  transition: background-color var(--transition);
}

.vocab-item:last-child {
  border-bottom: none;
}

.vocab-item:hover {
  background: color-mix(in srgb, var(--muted) 58%, var(--card) 42%);
}

.vocab-term {
  font-family: var(--font-display);
  font-size: 1.28rem;
  line-height: 1.28;
  margin-bottom: 4px;
}

.vocab-chinese {
  color: color-mix(in srgb, var(--accent) 82%, var(--foreground) 18%);
  font-size: 0.98rem;
  margin-bottom: 4px;
}

.vocab-definition {
  color: var(--muted-foreground);
  font-size: 0.94rem;
  font-style: italic;
  margin-bottom: 8px;
}

.vocab-note {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 1px solid color-mix(in srgb, var(--accent) 36%, var(--border) 64%);
  background: color-mix(in srgb, var(--accent) 10%, var(--card) 90%);
  color: color-mix(in srgb, var(--accent) 88%, var(--foreground) 12%);
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  padding: 4px 8px;
  margin-bottom: 9px;
}

.examples-list {
  margin-top: 6px;
}

.example-pair {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(0, 0.7fr);
  gap: 7px 18px;
  border-top: 1px dashed var(--border);
  padding: 8px 0;
  font-size: 0.95rem;
  line-height: 1.65;
}

.example-pair:first-child {
  border-top: none;
}

.example-en {
  color: color-mix(in srgb, var(--foreground) 92%, var(--muted-foreground) 8%);
}

.example-zh {
  color: var(--muted-foreground);
}

.related-section {
  margin-top: 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--card);
  box-shadow: var(--shadow-sm);
  padding: 16px;
}

.related-label {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
}

.related-label::before,
.related-label::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--border);
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 10px;
}

.related-card {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--card);
  padding: 10px 12px;
  display: flex;
  align-items: center;
  gap: 10px;
  text-align: left;
  transition: border-color var(--transition), box-shadow var(--transition), background-color var(--transition);
}

.related-card:hover {
  border-color: color-mix(in srgb, var(--accent) 52%, var(--border) 48%);
  background: color-mix(in srgb, var(--accent) 5%, var(--card) 95%);
  box-shadow: var(--shadow-sm);
}

.related-num {
  min-width: 38px;
  height: 28px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border);
  background: var(--muted);
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  color: var(--muted-foreground);
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.related-info {
  min-width: 0;
}

.related-title {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.25;
  margin-bottom: 2px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.related-zh {
  color: var(--muted-foreground);
  font-size: 0.84rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.notebook-block {
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--accent) 4%, var(--card) 96%), var(--card) 36%),
    var(--card);
}

.notebook-overview {
  padding: 20px 22px 6px;
}

.notebook-kicker {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.notebook-doc-title {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 1.25rem + 0.8vw, 2rem);
  line-height: 1.15;
  margin-bottom: 12px;
}

.notebook-overview-zh {
  font-size: 1rem;
  line-height: 1.8;
  color: color-mix(in srgb, var(--foreground) 90%, var(--muted-foreground) 10%);
  margin-bottom: 10px;
}

.notebook-overview-en {
  font-size: 0.92rem;
  line-height: 1.75;
  color: var(--muted-foreground);
}

.notebook-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 14px;
  align-items: center;
  margin-top: 14px;
}

.notebook-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  padding: 0 22px 22px;
}

.notebook-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--muted) 62%, var(--card) 38%);
  padding: 16px;
  height: 100%;
  display: flex;
  flex-direction: column;
}

.notebook-card-label {
  display: inline-flex;
  align-items: center;
  min-height: 24px;
  border: 1px solid color-mix(in srgb, var(--accent) 38%, var(--border) 62%);
  border-radius: var(--radius-pill);
  padding: 2px 10px;
  margin-bottom: 10px;
  font-family: var(--font-mono);
  font-size: 0.66rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--accent) 82%, var(--foreground) 18%);
  background: color-mix(in srgb, var(--accent) 10%, var(--card) 90%);
}

.notebook-card-en {
  font-size: 0.94rem;
  line-height: 1.35;
  color: var(--foreground);
  margin-bottom: 10px;
}

.notebook-card-zh {
  font-size: 0.86rem;
  line-height: 1.75;
  color: var(--muted-foreground);
}

.source-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 12px;
  padding: 18px;
}

.source-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--muted) 58%, var(--card) 42%);
  padding: 16px;
  display: grid;
  gap: 10px;
}

.source-card-muted {
  background: color-mix(in srgb, var(--muted) 72%, var(--card) 28%);
}

.source-kind {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: var(--accent);
}

.source-title {
  font-family: var(--font-display);
  font-size: 1.08rem;
  line-height: 1.35;
  color: var(--foreground);
}

.source-meta {
  font-size: 0.84rem;
  line-height: 1.65;
  color: var(--muted-foreground);
}

.source-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 14px;
  align-items: center;
}

.source-link {
  display: inline-flex;
  align-items: center;
  justify-self: start;
  min-height: 34px;
  padding: 6px 12px;
  border: 1px solid color-mix(in srgb, var(--accent) 36%, var(--border) 64%);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--accent) 10%, var(--card) 90%);
  color: color-mix(in srgb, var(--accent) 86%, var(--foreground) 14%);
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.source-link:hover {
  text-decoration: none;
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 18%, var(--card) 82%);
}

.source-sub-link {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--muted-foreground);
}

.source-sub-link:hover {
  color: var(--accent);
  text-decoration: none;
}

mark {
  background: color-mix(in srgb, var(--accent-secondary) 35%, #fff4d8 65%);
  color: inherit;
  border-radius: 2px;
  padding: 0 2px;
}

.sidebar-toggle {
  display: none;
  position: fixed;
  left: 16px;
  bottom: 20px;
  width: 48px;
  height: 48px;
  min-height: 48px;
  border: 1px solid color-mix(in srgb, var(--accent) 46%, var(--border) 54%);
  border-radius: 50%;
  background: color-mix(in srgb, var(--accent) 90%, var(--accent-secondary) 10%);
  color: var(--accent-foreground);
  box-shadow: var(--shadow-md);
  font-size: 1.2rem;
}

.sidebar::-webkit-scrollbar {
  width: 6px;
}

.sidebar::-webkit-scrollbar-thumb {
  background: color-mix(in srgb, var(--border) 82%, #d8d2cb 18%);
  border-radius: 8px;
}

@media (max-width: 1120px) {
  .layout {
    grid-template-columns: minmax(220px, 268px) minmax(0, 1fr);
    gap: 20px;
  }

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

  .hero-stats {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .detail-layout {
    grid-template-columns: 1fr;
    grid-template-areas:
      "rail"
      "primary";
  }

  .detail-rail {
    position: static;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .panel-header h2 {
    font-size: clamp(1.85rem, 1.3rem + 2vw, 2.35rem);
  }

  .notebook-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 900px) {
  :root {
    --header-height: 80px;
  }

  .layout {
    display: block;
    padding: 20px 16px 96px;
    padding: 20px 16px calc(96px + env(safe-area-inset-bottom));
  }

  .sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    width: min(90vw, 320px);
    max-height: calc(100vh - var(--header-height));
    border-radius: 0 12px 12px 0;
    border-left: none;
    box-shadow: var(--shadow-lg);
    transform: translateX(-102%);
    transition: transform 240ms ease;
    z-index: 160;
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .sidebar-toggle {
    display: grid;
    place-items: center;
    left: auto;
    right: 18px;
    bottom: 18px;
    bottom: calc(18px + env(safe-area-inset-bottom));
  }

  .main-content {
    padding-top: 4px;
  }

  .hero-shell {
    padding: 24px 20px 20px;
    border-radius: 22px;
  }

  .hero-title {
    max-width: none;
  }

  .hero-stats,
  .detail-stat-strip,
  .detail-rail,
  .detail-footer-grid {
    grid-template-columns: 1fr;
  }

  .context-bar {
    flex-direction: column;
    align-items: stretch;
    gap: 14px;
    padding: 14px;
    margin-bottom: 18px;
  }

  .lesson-grid {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .panel-header {
    align-items: flex-start;
    gap: 8px 12px;
  }

  .panel-header h2 {
    font-size: clamp(1.7rem, 1.34rem + 2.4vw, 2.2rem);
  }

  .panel-lead {
    max-width: 60ch;
    margin-bottom: 18px;
  }

  .lesson-card {
    padding: 16px 16px 14px;
  }

  .card-title {
    font-size: 1.18rem;
  }

  .card-summary {
    font-size: 0.92rem;
    margin-bottom: 12px;
  }

  .card-footer {
    flex-wrap: wrap;
  }

  .detail-nav {
    display: grid;
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .detail-nav-arrows {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    width: 100%;
  }

  .btn-back,
  .btn-prev,
  .btn-next,
  .context-reset {
    width: 100%;
    justify-content: center;
  }

  .detail-header {
    padding: 24px 20px;
  }

  .detail-summary {
    font-size: 0.95rem;
  }

  .section-heading {
    padding: 12px 16px;
  }

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

  .detail-title {
    font-size: clamp(1.75rem, 1.4rem + 1vw, 2.2rem);
  }

  .example-pair {
    grid-template-columns: 1fr;
    gap: 3px;
  }

  .example-zh {
    padding-left: 10px;
    border-left: 1px solid var(--border);
  }
}

@media (max-width: 760px) {
  :root {
    --header-height: 124px;
  }

  .header-inner {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
    padding: 12px 16px 14px;
  }

  .header-brand,
  .header-search {
    width: 100%;
  }

  .header-search input {
    min-height: 46px;
  }
}

@media (max-width: 680px) {
  :root {
    --header-height: 118px;
  }

  .header-inner {
    padding: 12px 14px 14px;
    gap: 10px;
  }

  .hero-shell {
    padding: 20px 16px 16px;
  }

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

  .hero-action,
  .context-reset {
    width: 100%;
    justify-content: center;
  }

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

  .brand-icon {
    width: 36px;
    height: 36px;
    font-size: 16px;
  }

  .brand-text p {
    display: none;
  }

  .brand-text h1 {
    font-size: 1.05rem;
  }

  .header-search {
    width: 100%;
  }

  .header-search input {
    min-height: 46px;
    font-size: 0.93rem;
    padding-left: 42px;
    padding-right: 42px;
  }

  .search-icon {
    left: 14px;
  }

  .panel-kicker {
    gap: 8px;
  }

  .kicker-text {
    font-size: 0.68rem;
    letter-spacing: 0.12em;
  }

  .panel-header {
    gap: 8px;
  }

  .panel-header h2 {
    font-size: clamp(1.52rem, 1.26rem + 2.2vw, 1.9rem);
  }

  .result-count {
    font-size: 0.7rem;
  }

  .panel-lead {
    font-size: 0.92rem;
    margin-bottom: 14px;
  }

  .context-bar {
    gap: 12px;
    border-radius: 16px;
    padding: 12px;
    margin-bottom: 16px;
  }

  .context-label {
    font-size: 0.66rem;
    letter-spacing: 0.12em;
  }

  .context-description {
    font-size: 0.88rem;
    line-height: 1.55;
  }

  .lesson-grid {
    gap: 12px;
  }

  .lesson-card {
    padding: 15px 14px 13px;
  }

  .card-number {
    margin-bottom: 6px;
  }

  .card-number-value {
    font-size: 1.18rem;
  }

  .card-title {
    font-size: 1.08rem;
  }

  .card-chinese {
    font-size: 0.9rem;
    margin-bottom: 8px;
  }

  .card-summary {
    -webkit-line-clamp: 4;
    font-size: 0.9rem;
  }

  .card-category {
    min-height: 30px;
    padding: 4px 9px;
  }

  .detail-nav {
    margin-bottom: 12px;
  }

  .detail-header {
    padding: 20px 16px;
  }

  .detail-title {
    font-size: clamp(1.48rem, 1.2rem + 3vw, 1.85rem);
  }

  .detail-chinese-title {
    font-size: 0.96rem;
    margin-bottom: 12px;
  }

  .detail-meta {
    gap: 6px;
    margin-bottom: 12px;
  }

  .detail-category,
  .detail-tag {
    min-height: 28px;
    font-size: 0.66rem;
  }

  .detail-summary {
    padding: 10px 12px;
  }

  .btn-back,
  .btn-prev,
  .btn-next,
  .context-reset,
  .source-link,
  .job-lesson-open {
    min-height: 46px;
  }

  .detail-jump-card {
    min-height: 108px;
    padding: 16px;
  }

  .section-heading,
  .vocab-item {
    padding-left: 14px;
    padding-right: 14px;
  }

  .section-heading::before,
  .section-heading::after {
    display: none;
  }

  .vocab-term {
    font-size: 1.12rem;
  }

  .vocab-chinese {
    font-size: 0.92rem;
  }

  .vocab-definition,
  .example-pair {
    font-size: 0.9rem;
  }

  .notebook-overview,
  .source-grid {
    padding-left: 14px;
    padding-right: 14px;
  }

  .source-grid {
    gap: 10px;
    padding-top: 14px;
    padding-bottom: 14px;
  }

  .source-card {
    padding: 14px;
    gap: 8px;
  }

  .notebook-grid {
    grid-template-columns: 1fr;
    gap: 10px;
    padding: 0 14px 14px;
  }

  .notebook-card {
    padding: 14px;
  }

  .related-section {
    padding: 14px;
  }

  .layout {
    padding: 16px 12px 92px;
    padding: 16px 12px calc(92px + env(safe-area-inset-bottom));
  }

  .sidebar {
    width: min(92vw, 320px);
  }

  .sidebar-toggle {
    right: 14px;
    bottom: 14px;
    bottom: calc(14px + env(safe-area-inset-bottom));
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

@keyframes fade-in {
  from {
    opacity: 0;
  }

  to {
    opacity: 1;
  }
}