/* =========================================================
   知之學習網 — Design System
   溫暖青綠 + 琥珀強調 · mobile-first · Noto Sans TC
   ========================================================= */

:root {
  /* Brand */
  --color-primary-50: #f0fdfa;
  --color-primary-100: #ccfbf1;
  --color-primary-200: #99f6e4;
  --color-primary-500: #14b8a6;
  --color-primary-600: #0d9488;
  --color-primary-700: #0f766e;
  --color-primary-800: #115e59;
  --color-primary-900: #134e4a;

  --color-accent-100: #fef3c7;
  --color-accent-400: #fbbf24;
  --color-accent-500: #f59e0b;
  --color-accent-600: #d97706;
  --color-accent-700: #b45309;

  --color-success: #059669;
  --color-warning: #d97706;
  --color-danger: #dc2626;
  --color-info: #0284c7;

  /* Semantic surfaces (light) */
  --bg: #fbfaf6;
  --bg-elevated: #fffefb;
  --bg-muted: #f2f0e8;
  --bg-header: rgba(251, 250, 246, 0.94);
  --text: #102a43;
  --text-secondary: #385169;
  --text-muted: #526a7d;
  --border: #d9ddd7;
  --border-strong: #b8c4c2;
  --shadow: 0 1px 2px rgba(15, 61, 56, 0.06), 0 8px 24px rgba(15, 61, 56, 0.06);
  --shadow-sm: 0 1px 2px rgba(15, 61, 56, 0.05);
  --ring: #0f766e;
  --overlay: rgba(15, 40, 36, 0.4);

  --primary: var(--color-primary-700);
  --primary-hover: var(--color-primary-800);
  --primary-soft: var(--color-primary-100);
  --accent: var(--color-accent-500);
  --accent-soft: var(--color-accent-100);

  /* Typography */
  --font: "Noto Sans TC", "Microsoft JhengHei", "PingFang TC", "Helvetica Neue",
    Arial, sans-serif;
  --fs-xs: 0.75rem;
  --fs-sm: 0.875rem;
  --fs-base: 1rem;
  --fs-md: 1.0625rem;
  --fs-lg: 1.25rem;
  --fs-xl: 1.5rem;
  --fs-2xl: 1.875rem;
  --fs-3xl: 2.25rem;
  --lh: 1.65;
  --lh-tight: 1.3;

  /* Spacing / radius / layout */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --radius-sm: 0.5rem;
  --radius: 0.75rem;
  --radius-lg: 1rem;
  --radius-full: 9999px;
  --touch: 44px;
  --header-h: 64px;
  --nav-h: 64px;
  --max-w: 1240px;
  --content-w: 720px;

  /* Safe area */
  --sat: env(safe-area-inset-top, 0px);
  --sar: env(safe-area-inset-right, 0px);
  --sab: env(safe-area-inset-bottom, 0px);
  --sal: env(safe-area-inset-left, 0px);

  color-scheme: light;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0f1716;
  --bg-elevated: #182422;
  --bg-muted: #1f302d;
  --bg-header: rgba(15, 23, 22, 0.92);
  --text: #e8f2ef;
  --text-secondary: #b7ccc6;
  --text-muted: #8aa39c;
  --border: #2a403b;
  --border-strong: #3a554f;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.35), 0 10px 28px rgba(0, 0, 0, 0.35);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --ring: #5eead4;
  --overlay: rgba(0, 0, 0, 0.55);

  --primary: #2dd4bf;
  --primary-hover: #5eead4;
  --primary-soft: rgba(45, 212, 191, 0.14);
  --accent: #fbbf24;
  --accent-soft: rgba(251, 191, 36, 0.16);

  --color-success: #34d399;
  --color-warning: #fbbf24;
  --color-danger: #f87171;
  --color-info: #38bdf8;
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

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

body {
  margin: 0;
  min-height: 100dvh;
  font-family: var(--font);
  font-size: var(--fs-base);
  line-height: var(--lh);
  color: var(--text);
  background:
    radial-gradient(1200px 500px at 10% -10%, rgba(13, 148, 136, 0.08), transparent 55%),
    radial-gradient(900px 400px at 100% 0%, rgba(245, 158, 11, 0.08), transparent 50%),
    var(--bg);
  padding-top: calc(var(--header-h) + var(--sat));
  padding-bottom: calc(var(--nav-h) + var(--sab) + var(--space-4));
  padding-left: var(--sal);
  padding-right: var(--sar);
}

img,
svg {
  display: block;
  max-width: 100%;
}

a {
  color: var(--primary);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.15em;
}

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

:focus-visible {
  outline: 3px solid var(--ring);
  outline-offset: 2px;
}

.skip-link {
  position: absolute;
  left: var(--space-4);
  top: -100px;
  z-index: 1000;
  padding: var(--space-3) var(--space-4);
  background: var(--primary);
  color: #fff;
  border-radius: var(--radius-sm);
  font-weight: 600;
}

.skip-link:focus {
  top: calc(var(--sat) + var(--space-2));
}

/* ---------- Header ---------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: calc(var(--header-h) + var(--sat));
  padding-top: var(--sat);
  background: var(--bg-header);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.header-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  height: var(--header-h);
  padding: 0 var(--space-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.brand {
  display: flex;
  min-height: var(--touch);
  align-items: center;
  gap: var(--space-3);
  min-width: 0;
  color: inherit;
  text-decoration: none;
}

.brand:hover {
  color: inherit;
}

.brand-mark {
  flex: 0 0 auto;
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
  border-radius: var(--radius);
  background: linear-gradient(145deg, var(--color-primary-600), var(--color-primary-800));
  color: #fff;
  font-weight: 700;
  font-size: var(--fs-lg);
  box-shadow: var(--shadow-sm);
}

.brand-text {
  display: flex;
  flex-direction: column;
  min-width: 0;
  line-height: var(--lh-tight);
}

.brand-title {
  font-weight: 700;
  font-size: var(--fs-sm);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.brand-sub {
  font-size: var(--fs-xs);
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex: 0 0 auto;
}

.field {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.field-label {
  font-size: var(--fs-xs);
  color: var(--text-muted);
  font-weight: 600;
}

.select {
  min-height: var(--touch);
  min-width: 5.5rem;
  padding: 0 var(--space-3);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--bg-elevated);
  color: var(--text);
  font: inherit;
  font-size: var(--fs-sm);
  font-weight: 600;
}

/* ---------- Main / app shell ---------- */
.site-main {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: var(--space-4);
}

.app {
  min-height: 40vh;
}

/* ---------- Bottom nav ---------- */
.bottom-nav {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 100;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  height: calc(var(--nav-h) + var(--sab));
  padding-bottom: var(--sab);
  background: var(--bg-header);
  border-top: 1px solid var(--border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.nav-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  min-height: var(--nav-h);
  color: var(--text-muted);
  text-decoration: none;
  font-size: var(--fs-xs);
  font-weight: 600;
  -webkit-tap-highlight-color: transparent;
}

.nav-item:hover {
  color: var(--primary);
}

.nav-item.is-active {
  color: var(--primary);
}

.nav-item.is-active .nav-icon {
  background: var(--primary-soft);
}

.nav-icon {
  width: 32px;
  height: 28px;
  display: grid;
  place-items: center;
  border-radius: var(--radius-sm);
  font-size: 1.1rem;
  line-height: 1;
}

/* ---------- Typography helpers ---------- */
.page-title {
  margin: 0 0 var(--space-2);
  font-size: var(--fs-2xl);
  line-height: var(--lh-tight);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.section-title {
  margin: 0 0 var(--space-3);
  font-size: var(--fs-lg);
  font-weight: 700;
}

.lead {
  margin: 0 0 var(--space-6);
  color: var(--text-secondary);
  font-size: var(--fs-md);
}

.muted {
  color: var(--text-muted);
}

.warn-text {
  color: var(--color-warning);
  font-weight: 600;
}

/* ---------- Cards / surfaces ---------- */
.card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  padding: var(--space-4);
}

.card-link {
  display: block;
  color: inherit;
  text-decoration: none;
  transition: border-color 0.15s ease, transform 0.15s ease, box-shadow 0.15s ease;
}

.card-link:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow);
  color: inherit;
  transform: translateY(-1px);
}

.card-link:active {
  transform: translateY(0);
}

.grid {
  display: grid;
  gap: var(--space-3);
}

.grid-2 {
  grid-template-columns: 1fr;
}

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

.stack {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-3);
}

.cluster {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: var(--touch);
  min-width: var(--touch);
  padding: 0 var(--space-4);
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  background: var(--bg-muted);
  color: var(--text);
  font: inherit;
  font-weight: 600;
  font-size: var(--fs-sm);
  cursor: pointer;
  text-decoration: none;
  -webkit-tap-highlight-color: transparent;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.btn:hover {
  color: inherit;
  filter: brightness(0.98);
}

.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

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

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

.btn-accent {
  background: var(--accent);
  color: #1c1917;
}

.btn-ghost {
  background: transparent;
  border-color: var(--border-strong);
}

.btn-ghost:hover {
  background: var(--bg-muted);
}

.btn-icon {
  width: var(--touch);
  padding: 0;
}

.btn-block {
  width: 100%;
}

[data-theme="light"] .theme-icon-dark,
html:not([data-theme="dark"]) .theme-icon-dark {
  display: none;
}

[data-theme="dark"] .theme-icon-light {
  display: none;
}

/* ---------- Badge / chips ---------- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35em;
  min-height: 1.75rem;
  padding: 0.15rem 0.6rem;
  border-radius: var(--radius-full);
  background: var(--bg-muted);
  color: var(--text-secondary);
  font-size: var(--fs-xs);
  font-weight: 700;
  line-height: 1.2;
  white-space: nowrap;
}

.badge-teal {
  background: var(--primary-soft);
  color: var(--color-primary-800);
}

[data-theme="dark"] .badge-teal {
  color: var(--primary);
}

.badge-amber {
  background: var(--accent-soft);
  color: var(--color-accent-700);
}

[data-theme="dark"] .badge-amber {
  color: var(--accent);
}

.badge-ok {
  background: rgba(5, 150, 105, 0.14);
  color: var(--color-success);
}

/* ---------- Progress bar ---------- */
.progress {
  --value: 0%;
  height: 0.55rem;
  border-radius: var(--radius-full);
  background: var(--bg-muted);
  overflow: hidden;
}

.progress > span {
  display: block;
  height: 100%;
  width: var(--value);
  border-radius: inherit;
  background: linear-gradient(90deg, var(--color-primary-600), var(--color-primary-500));
  transition: width 0.25s ease;
}

.progress-meta {
  display: flex;
  justify-content: space-between;
  gap: var(--space-2);
  margin-bottom: var(--space-2);
  font-size: var(--fs-sm);
  color: var(--text-secondary);
  font-weight: 600;
}

/* ---------- Hero / home ---------- */
.hero {
  padding: var(--space-6);
  border-radius: var(--radius-lg);
  background:
    linear-gradient(135deg, rgba(15, 118, 110, 0.1), rgba(245, 158, 11, 0.08)),
    var(--bg-elevated);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  margin-bottom: var(--space-6);
}

.hero h1 {
  margin: 0 0 var(--space-3);
  font-size: clamp(1.5rem, 4vw, 2rem);
  line-height: var(--lh-tight);
}

.hero p {
  margin: 0 0 var(--space-5);
  color: var(--text-secondary);
  max-width: 40rem;
}

.stat-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-3);
  margin-bottom: var(--space-6);
}

.stat-card strong {
  display: block;
  font-size: var(--fs-xl);
  color: var(--primary);
  line-height: 1.2;
}

.stat-card span {
  font-size: var(--fs-sm);
  color: var(--text-muted);
}

/* ---------- Subject cards ---------- */
.subject-card {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  min-height: 140px;
}

.subject-card .icon-bubble {
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border-radius: var(--radius);
  background: var(--primary-soft);
  color: var(--primary);
  font-size: 1.25rem;
  font-weight: 700;
}

.subject-card h3 {
  margin: 0;
  font-size: var(--fs-md);
}

.subject-card p {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--fs-sm);
  flex: 1;
}

/* ---------- Unit list ---------- */
.unit-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.unit-item {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.unit-item-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-3);
}

.unit-item h3 {
  margin: 0 0 var(--space-1);
  font-size: var(--fs-md);
}

.unit-item p {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--fs-sm);
}

.unit-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* ---------- Lesson prose ---------- */
.lesson {
  max-width: var(--content-w);
}

.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.lesson-section {
  margin-bottom: var(--space-6);
}

.lesson-section h2 {
  margin: 0 0 var(--space-3);
  font-size: var(--fs-lg);
  padding-bottom: var(--space-2);
  border-bottom: 2px solid var(--primary-soft);
}

.lesson-prose {
  color: var(--text-secondary);
}

.lesson-prose p {
  margin: 0 0 var(--space-3);
}

.lesson-prose ul,
.lesson-prose ol {
  margin: 0 0 var(--space-3);
  padding-left: 1.25rem;
}

.lesson-prose li {
  margin-bottom: var(--space-2);
}

.lesson-prose strong {
  color: var(--text);
}

.goals-list {
  margin: 0;
  padding-left: 1.2rem;
}

.goals-list li {
  margin-bottom: var(--space-2);
}

.example-box {
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: var(--space-4);
  margin: var(--space-3) 0;
}

.example-box h3 {
  margin: 0 0 var(--space-2);
  font-size: var(--fs-base);
  color: var(--color-accent-700);
}

[data-theme="dark"] .example-box h3 {
  color: var(--accent);
}

.summary-box {
  background: var(--primary-soft);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-4);
}

.lesson-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-top: var(--space-6);
  padding-top: var(--space-4);
  border-top: 1px solid var(--border);
}

/* ---------- Breadcrumb ---------- */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  margin: 0 0 var(--space-4);
  padding: 0;
  list-style: none;
  font-size: var(--fs-sm);
  color: var(--text-muted);
}

.breadcrumb a {
  display: inline-flex;
  min-height: var(--touch);
  min-width: var(--touch);
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 600;
}

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

.breadcrumb li:not(:last-child)::after {
  content: "/";
  margin-left: var(--space-2);
  color: var(--text-muted);
  font-weight: 400;
}

/* ---------- Search ---------- */
.search-form {
  display: flex;
  gap: var(--space-2);
  margin-bottom: var(--space-5);
}

.search-input {
  flex: 1;
  min-height: var(--touch);
  padding: 0 var(--space-4);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--bg-elevated);
  color: var(--text);
  font: inherit;
  font-size: var(--fs-md);
}

.search-input::placeholder {
  color: var(--text-muted);
}

.search-hit {
  display: block;
}

.search-hit h3 {
  margin: 0 0 var(--space-1);
  font-size: var(--fs-md);
}

.search-hit p {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--fs-sm);
}

mark {
  background: var(--accent-soft);
  color: inherit;
  padding: 0 0.15em;
  border-radius: 0.2em;
}

/* ---------- Quiz ---------- */
.quiz-header {
  margin-bottom: var(--space-4);
}

.quiz-list {
  list-style: none;
  margin: 0 0 var(--space-5);
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.quiz-item {
  transition: border-color 0.15s ease;
}

.quiz-item.is-correct {
  border-color: var(--color-success);
}

.quiz-item.is-wrong {
  border-color: var(--color-danger);
}

.quiz-prompt {
  font-weight: 600;
  margin-bottom: var(--space-3);
}

.quiz-num {
  color: var(--primary);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.quiz-option {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  min-height: var(--touch);
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg);
  cursor: pointer;
  transition: border-color 0.15s ease, background 0.15s ease;
}

.quiz-option:hover {
  border-color: var(--primary);
  background: var(--primary-soft);
}

.quiz-option:has(input:checked) {
  border-color: var(--primary);
  background: var(--primary-soft);
  box-shadow: inset 0 0 0 1px var(--primary);
}

.quiz-option input {
  margin-top: 0.2rem;
  width: 1.15rem;
  height: 1.15rem;
  accent-color: var(--color-primary-600);
  flex: 0 0 auto;
}

.quiz-option-text {
  flex: 1;
  line-height: 1.45;
}

.quiz-feedback {
  margin-top: var(--space-3);
  padding: var(--space-3);
  border-radius: var(--radius-sm);
  font-size: var(--fs-sm);
}

.quiz-feedback--ok {
  background: rgba(5, 150, 105, 0.12);
  color: var(--color-success);
}

.quiz-feedback--no {
  background: rgba(220, 38, 38, 0.1);
  color: var(--color-danger);
}

.quiz-explain {
  margin: var(--space-2) 0 0;
  color: var(--text-secondary);
  font-weight: 400;
}

.quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
}

.quiz-result {
  margin-top: var(--space-2);
}

.quiz-score {
  font-size: var(--fs-xl);
  margin-bottom: var(--space-2);
}

.quiz-score--good {
  color: var(--color-success);
}

.quiz-score--ok {
  color: var(--color-warning);
}

.quiz-score--low {
  color: var(--color-danger);
}

/* ---------- Empty / loading / noscript ---------- */
.empty-state,
.loading-state {
  text-align: center;
  padding: var(--space-8) var(--space-4);
}

.empty-state h2,
.loading-state p {
  margin: 0 0 var(--space-3);
}

.empty-state p {
  margin: 0 auto var(--space-5);
  max-width: 28rem;
  color: var(--text-secondary);
}

.empty-icon {
  font-size: 2.5rem;
  margin-bottom: var(--space-3);
  line-height: 1;
}

.spinner {
  width: 36px;
  height: 36px;
  margin: 0 auto var(--space-4);
  border: 3px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

.noscript-banner {
  position: fixed;
  inset: auto var(--space-4) calc(var(--nav-h) + var(--sab) + var(--space-4));
  z-index: 200;
  padding: var(--space-4);
  background: var(--accent-soft);
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

code.inline {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
  padding: 0.1em 0.35em;
  border-radius: 0.3em;
  background: var(--bg-muted);
}

/* ---------- Grade chips ---------- */
.grade-grid {
  display: grid;
  gap: var(--space-3);
}

.grade-card h2 {
  margin: 0 0 var(--space-2);
  font-size: var(--fs-xl);
}

.grade-card p {
  margin: 0 0 var(--space-4);
  color: var(--text-muted);
}

/* ---------- Progress page ---------- */
.progress-summary {
  display: grid;
  gap: var(--space-3);
  margin-bottom: var(--space-6);
}

.progress-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.progress-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

/* ---------- Publisher / Junyi / Mastery ---------- */
.publisher-field .field-label {
  display: none;
}

@media (min-width: 768px) {
  .publisher-field .field-label {
    display: inline;
  }
}

.publisher-bar {
  margin-bottom: var(--space-4);
  padding: var(--space-4);
}

.publisher-bar-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
}

.pub-chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.pub-chip {
  min-height: var(--touch);
  padding: 0.5rem 1rem;
  border-radius: var(--radius-full);
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
  color: var(--text);
  font: inherit;
  font-weight: 600;
  font-size: var(--fs-sm);
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

a.pub-chip {
  color: inherit;
}

.pub-chip:hover {
  border-color: var(--primary);
  background: var(--primary-soft);
}

.pub-chip.is-active {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.publisher-note {
  margin: var(--space-3) 0 0;
  font-size: var(--fs-sm);
  line-height: 1.5;
}

.junyi-banner {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
  padding: var(--space-4);
  border-left: 4px solid var(--color-info);
  background: linear-gradient(135deg, var(--bg-elevated), var(--bg-muted));
}

.junyi-banner-text p {
  margin: var(--space-2) 0 0;
}

.junyi-banner-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.mastery-badge {
  display: inline-flex;
  align-items: center;
  min-height: 1.75rem;
  padding: 0.15rem 0.6rem;
  border-radius: var(--radius-full);
  font-size: var(--fs-xs);
  font-weight: 700;
  letter-spacing: 0.02em;
}

.mastery-not_started {
  background: var(--bg-muted);
  color: var(--text-muted);
}

.mastery-attempted {
  background: #e0f2fe;
  color: #0369a1;
}

.mastery-familiar {
  background: #fef3c7;
  color: #b45309;
}

.mastery-proficient {
  background: #d1fae5;
  color: #047857;
}

.mastery-mastered {
  background: #ccfbf1;
  color: #0f766e;
  box-shadow: inset 0 0 0 1px rgba(15, 118, 110, 0.25);
}

[data-theme="dark"] .mastery-attempted {
  background: #0c4a6e;
  color: #bae6fd;
}

[data-theme="dark"] .mastery-familiar {
  background: #78350f;
  color: #fde68a;
}

[data-theme="dark"] .mastery-proficient {
  background: #064e3b;
  color: #a7f3d0;
}

[data-theme="dark"] .mastery-mastered {
  background: #134e4a;
  color: #99f6e4;
}

.unit-schedule-meta {
  margin: 0 0 var(--space-2) !important;
  font-size: var(--fs-sm);
}

.unit-list-path {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  position: relative;
}

.unit-list-path::before {
  content: "";
  position: absolute;
  left: 1.1rem;
  top: 0.5rem;
  bottom: 0.5rem;
  width: 3px;
  background: linear-gradient(var(--primary-soft), var(--border));
  border-radius: var(--radius-full);
  pointer-events: none;
  opacity: 0.7;
}

@media (max-width: 767px) {
  .unit-list-path::before {
    display: none;
  }
}

.schedule-filters {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  margin-bottom: var(--space-4);
}

.schedule-filters .field-label {
  display: block;
  font-size: var(--fs-sm);
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: var(--space-2);
}

.schedule-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

.schedule-col h3 {
  margin: 0 0 var(--space-3);
  font-size: var(--fs-lg);
}

.schedule-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.schedule-list li {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  gap: var(--space-2);
  padding: var(--space-2) 0;
  border-bottom: 1px solid var(--border);
}

.schedule-list a {
  display: flex;
  gap: var(--space-2);
  flex: 1;
  min-width: 0;
  text-decoration: none;
  color: inherit;
}

.schedule-list a:hover strong {
  color: var(--primary);
}

.sched-order {
  flex-shrink: 0;
  width: 1.75rem;
  height: 1.75rem;
  border-radius: var(--radius-full);
  background: var(--primary-soft);
  color: var(--primary);
  font-size: var(--fs-xs);
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.sched-body {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  min-width: 0;
}

.sched-body strong {
  font-size: var(--fs-sm);
  line-height: 1.4;
}

@media (min-width: 900px) {
  .schedule-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .junyi-banner {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }
}

/* ---------- Breakpoints ---------- */
/* 640 */
@media (min-width: 640px) {
  .brand-title {
    font-size: var(--fs-base);
  }

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

  .stat-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

/* 768 */
@media (min-width: 768px) {
  :root {
    --header-h: 72px;
  }

  .site-main {
    padding: var(--space-6);
  }

  .grid-subjects {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .grade-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .unit-item {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }

  .unit-actions {
    flex-shrink: 0;
  }
}

/* 1024 — bottom nav still useful on iPad landscape; add side breathing room */
@media (min-width: 1024px) {
  .grid-subjects {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .hero {
    padding: var(--space-8);
  }

  /* Optional desktop top spacing when bottom nav remains */
  body {
    padding-bottom: calc(var(--nav-h) + var(--sab) + var(--space-6));
  }
}

/* 1280 */
@media (min-width: 1280px) {
  .grid-subjects {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .site-main {
    padding-left: var(--space-8);
    padding-right: var(--space-8);
  }
}

/* Desktop: keep bottom nav for consistency across phone/tablet/desktop goal */
@media (min-width: 768px) {
  .nav-label {
    font-size: var(--fs-sm);
  }
}

/* =========================================================
   Editorial learning layout — 2026 lesson refresh
   ========================================================= */

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

body {
  background:
    linear-gradient(rgba(15, 118, 110, 0.025) 1px, transparent 1px) 0 0 / 100% 2rem,
    var(--bg);
}

.desktop-nav {
  display: none;
}

.badge {
  white-space: normal;
  text-align: center;
}

.search-input {
  min-width: 0;
}

.home-hero {
  position: relative;
  display: grid;
  overflow: hidden;
  margin-bottom: var(--space-10);
  border-bottom: 1px solid var(--border);
  background: var(--bg-elevated);
}

.home-hero-copy {
  position: relative;
  z-index: 1;
  padding: clamp(2rem, 7vw, 5.5rem) var(--space-5) var(--space-8);
}

.home-hero h1 {
  max-width: 11ch;
  margin: 0 0 var(--space-4);
  color: var(--text);
  font-size: clamp(2.5rem, 8vw, 5rem);
  line-height: 1.08;
  letter-spacing: -0.055em;
}

.home-hero-lead {
  max-width: 24rem;
  margin: 0 0 var(--space-6);
  color: var(--text-secondary);
  font-size: clamp(1.1rem, 2.4vw, 1.5rem);
  font-weight: 600;
}

.home-primary-action {
  min-height: 3.35rem;
  padding-inline: var(--space-6);
  font-size: var(--fs-base);
}

.continue-card {
  display: grid;
  gap: 0.2rem;
  max-width: 34rem;
  margin-top: var(--space-6);
  padding: var(--space-4) 0 var(--space-4) var(--space-5);
  border-left: 2px solid #e8795d;
}

.continue-card > span,
.continue-card small {
  color: var(--text-muted);
  font-size: var(--fs-sm);
}

.continue-card strong {
  font-size: var(--fs-md);
}

.home-hero-media {
  min-height: 16rem;
  margin: 0;
  background: var(--bg-elevated);
}

.home-hero-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.home-learning {
  display: grid;
  gap: var(--space-10);
}

.home-section-head {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  align-items: flex-start;
  justify-content: space-between;
}

.home-section-head h2,
.learning-method h2,
.home-progress h2 {
  margin: 0;
  font-size: clamp(1.45rem, 3vw, 2rem);
  letter-spacing: -0.025em;
}

.home-section-head p,
.home-progress p {
  margin: var(--space-1) 0 0;
  color: var(--text-muted);
}

.home-section-head a,
.home-data-note a {
  align-items: center;
  display: inline-flex;
  min-height: var(--touch);
}

.subject-rail {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-top: 1px solid var(--border);
  border-left: 1px solid var(--border);
}

.subject-rail-item {
  display: flex;
  min-width: 0;
  align-items: center;
  gap: var(--space-3);
  min-height: 5.5rem;
  padding: var(--space-4);
  color: var(--text);
  text-decoration: none;
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  background: var(--bg-elevated);
  transition: background 0.15s ease, color 0.15s ease;
}

.subject-rail-item:hover {
  color: var(--primary);
  background: var(--primary-soft);
}

.subject-rail-item > span:last-child {
  min-width: 0;
}

.subject-rail-item strong,
.subject-rail-item small {
  display: block;
}

.subject-rail-item small {
  margin-top: 0.15rem;
  color: var(--text-muted);
}

.subject-rail-icon {
  display: grid;
  flex: 0 0 auto;
  width: 2.65rem;
  height: 2.65rem;
  place-items: center;
  color: var(--primary);
  border: 1px solid var(--border-strong);
  border-radius: 50%;
  font-weight: 800;
}

.learning-method {
  padding: var(--space-8) 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.learning-method > ol {
  display: grid;
  gap: var(--space-5);
  margin: var(--space-6) 0 0;
  padding: 0;
  list-style: none;
}

.learning-method li {
  display: flex;
  gap: var(--space-4);
  align-items: flex-start;
}

.learning-method li > span {
  display: grid;
  flex: 0 0 auto;
  width: 2rem;
  height: 2rem;
  place-items: center;
  color: #fff;
  border-radius: 50%;
  background: var(--primary);
  font-weight: 800;
}

.learning-method strong {
  font-size: var(--fs-md);
}

.learning-method p {
  margin: var(--space-1) 0 0;
  color: var(--text-muted);
}

.home-progress {
  display: grid;
  gap: var(--space-4);
  align-items: center;
  margin-top: var(--space-10);
  padding: var(--space-6) 0;
  border-top: 1px solid var(--border);
}

.home-stat {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
}

.home-stat strong {
  color: var(--primary);
  font-size: var(--fs-xl);
}

.home-stat span {
  color: var(--text-muted);
  font-size: var(--fs-sm);
}

.home-data-note {
  margin: var(--space-6) 0 0;
  color: var(--text-muted);
  font-size: var(--fs-sm);
}

.lesson {
  max-width: none;
}

.lesson-header {
  max-width: 54rem;
  padding: var(--space-2) 0 var(--space-4);
}

.lesson-header .page-title {
  margin-top: var(--space-3);
  font-size: clamp(2.25rem, 5vw, 3.75rem);
  letter-spacing: -0.055em;
}

h1[tabindex="-1"]:focus {
  outline: none;
}

.lesson-intro {
  max-width: 48rem;
  margin: var(--space-4) 0 0;
  color: var(--text-secondary);
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  line-height: 1.85;
}

.lesson-path {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 0 0 var(--space-6);
  padding: 0;
  list-style: none;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
}

.lesson-path li {
  display: flex;
  min-height: 4.35rem;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.lesson-path li:nth-child(2n) {
  border-right: 0;
}

.lesson-path li:nth-last-child(-n + 2) {
  border-bottom: 0;
}

.lesson-path li > span {
  display: grid;
  flex: 0 0 auto;
  width: 2rem;
  height: 2rem;
  place-items: center;
  border: 1px solid var(--border-strong);
  border-radius: 50%;
  font-weight: 800;
}

.lesson-path .is-current {
  color: var(--primary);
  background: var(--primary-soft);
}

.lesson-path .is-current > span {
  color: #fff;
  border-color: var(--primary);
  background: var(--primary);
}

.lesson-layout {
  display: grid;
  gap: var(--space-8);
  align-items: start;
}

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

.lesson-toc {
  padding: var(--space-4);
  border: 1px solid var(--border);
  background: var(--bg-elevated);
}

.lesson-toc > strong {
  display: block;
  margin-bottom: var(--space-3);
}

.lesson-toc ol {
  display: grid;
  gap: var(--space-1);
  margin: 0;
  padding: 0;
  list-style: none;
}

.lesson-toc button {
  display: flex;
  width: 100%;
  min-height: var(--touch);
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-2);
  color: var(--text-secondary);
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  font: inherit;
  font-size: var(--fs-sm);
  text-align: left;
  cursor: pointer;
}

.lesson-toc button:hover {
  color: var(--primary);
  background: var(--primary-soft);
}

.lesson-toc button span {
  display: grid;
  flex: 0 0 auto;
  width: 1.65rem;
  height: 1.65rem;
  place-items: center;
  color: var(--primary);
  border: 1px solid var(--border-strong);
  border-radius: 50%;
  font-size: var(--fs-xs);
  font-weight: 800;
}

.lesson-goals {
  margin-bottom: var(--space-6);
  padding: var(--space-5);
  border-left: 3px solid var(--primary);
  background: var(--primary-soft);
}

.lesson-goals h2,
.lesson-subsection h2,
.lesson-block-section h2,
.lesson-summary h2 {
  margin: 0;
  color: var(--text);
  font-size: clamp(1.35rem, 2.7vw, 1.75rem);
  letter-spacing: -0.02em;
}

.lesson-goals .goals-list {
  margin-top: var(--space-3);
}

.lesson-subsection,
.lesson-block-section,
.lesson-summary {
  scroll-margin-top: calc(var(--header-h) + 1.5rem);
  margin-bottom: clamp(2.5rem, 7vw, 4.5rem);
}

.lesson-visual-grid {
  display: grid;
  gap: var(--space-5);
  align-items: start;
}

.lesson-visual-grid .lesson-subsection,
.lesson-visual-grid .lesson-block-section {
  margin-bottom: var(--space-6);
}

.lesson-subsection {
  padding-top: var(--space-2);
}

.lesson-subsection h2 {
  margin-bottom: var(--space-4);
  padding-bottom: var(--space-3);
  border-bottom: 2px solid var(--primary);
}

.lesson-prose {
  color: var(--text-secondary);
  font-size: clamp(1.03rem, 1.8vw, 1.125rem);
  line-height: 1.85;
}

.key-list {
  display: grid;
  gap: var(--space-2);
  margin: var(--space-4) 0 0;
  padding: 0;
  list-style: none;
}

.key-list li {
  position: relative;
  padding-left: 1.5rem;
  color: var(--text-secondary);
}

.key-list li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--primary);
  font-weight: 800;
}

.section-heading {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin-bottom: var(--space-5);
}

.section-heading > span {
  display: grid;
  flex: 0 0 auto;
  width: 2.5rem;
  height: 2.5rem;
  place-items: center;
  color: #fff;
  border-radius: 50%;
  background: var(--primary);
  font-size: var(--fs-sm);
  font-weight: 800;
}

.section-heading p {
  margin: var(--space-1) 0 0;
  color: var(--text-muted);
}

.lesson-figure {
  overflow: hidden;
  margin: 0;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
}

.lesson-figure img {
  width: 100%;
  height: auto;
}

.lesson-figure figcaption {
  padding: var(--space-3) var(--space-4);
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
  font-size: var(--fs-sm);
  line-height: 1.6;
}

.equation-card {
  overflow: hidden;
  margin-bottom: var(--space-4);
  border: 1px solid var(--border);
  background: var(--bg-elevated);
}

.equation-card-head {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--border);
}

.equation-card-head > span {
  color: var(--primary);
  font-size: var(--fs-xl);
  font-weight: 800;
}

.equation-card-head h3 {
  margin: 0;
  font-size: var(--fs-base);
}

.equation-expression {
  overflow-x: auto;
  padding: var(--space-5) var(--space-4);
  color: var(--text);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: clamp(1.75rem, 6vw, 2.75rem);
  line-height: 1.25;
  text-align: center;
  white-space: nowrap;
}

.equation-reading {
  margin: 0;
  padding: 0 var(--space-4) var(--space-4);
  color: var(--text-secondary);
  line-height: 1.7;
}

.equation-steps {
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: equation-step;
  border-top: 1px solid var(--border);
}

.equation-steps li {
  position: relative;
  display: grid;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-4) var(--space-4) 3.75rem;
  counter-increment: equation-step;
  border-bottom: 1px solid var(--border);
}

.equation-steps li::before {
  content: counter(equation-step);
  position: absolute;
  top: var(--space-4);
  left: var(--space-4);
  display: grid;
  width: 1.7rem;
  height: 1.7rem;
  place-items: center;
  color: #fff;
  border-radius: 50%;
  background: var(--primary);
  font-size: var(--fs-xs);
  font-weight: 800;
}

.equation-steps p {
  margin: 0;
  color: var(--text-secondary);
}

.equation-step-expression {
  overflow-x: auto;
  color: var(--text);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: clamp(1.35rem, 4vw, 1.85rem);
  white-space: nowrap;
}

.lesson-tip {
  margin: 0;
  padding: var(--space-4);
  color: #8b2f22;
  background: #fff1ec;
}

[data-theme="dark"] .lesson-tip {
  color: #fecaca;
  background: rgba(190, 62, 47, 0.16);
}

.worked-example {
  margin-bottom: var(--space-5);
  padding: var(--space-5);
  border: 1px solid var(--border);
  border-left: 4px solid #e8795d;
  background: var(--bg-elevated);
}

.worked-example h3 {
  margin: 0 0 var(--space-4);
  font-size: var(--fs-lg);
}

.example-problem {
  display: grid;
  gap: var(--space-1);
  margin-bottom: var(--space-4);
  padding: var(--space-4);
  background: var(--bg-muted);
}

.example-problem p,
.solution-steps p,
.example-final,
.example-check {
  margin: 0;
}

.solution-steps {
  display: grid;
  gap: var(--space-3);
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: worked-step;
}

.solution-steps li {
  display: grid;
  gap: var(--space-3);
  padding: var(--space-4);
  counter-increment: worked-step;
  border-bottom: 1px solid var(--border);
}

.solution-steps li > div > strong::before {
  content: counter(worked-step) ". ";
  color: var(--primary);
}

.solution-steps p {
  color: var(--text-secondary);
  line-height: 1.7;
}

.solution-expression {
  display: block;
  overflow-x: auto;
  padding: var(--space-3);
  color: var(--text);
  border: 1px solid var(--border);
  background: var(--bg);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: clamp(1.2rem, 4vw, 1.6rem);
  white-space: nowrap;
}

.example-final,
.example-check {
  margin-top: var(--space-4);
  padding: var(--space-3) var(--space-4);
}

.example-final {
  color: var(--primary);
  background: var(--primary-soft);
}

.example-check {
  color: var(--text-secondary);
  background: var(--bg-muted);
}

.comparison-wrap {
  overflow-x: auto;
  margin-bottom: clamp(2.5rem, 7vw, 4.5rem);
}

.comparison-table {
  width: 100%;
  min-width: 42rem;
  border-collapse: collapse;
  background: var(--bg-elevated);
}

.comparison-table caption {
  padding: 0 0 var(--space-3);
  color: var(--text);
  font-size: var(--fs-lg);
  font-weight: 800;
  text-align: left;
}

.comparison-table th,
.comparison-table td {
  padding: var(--space-3);
  border: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}

.comparison-table thead th {
  background: var(--primary-soft);
}

.quick-check {
  margin-bottom: clamp(2.5rem, 7vw, 4.5rem);
  border: 1px solid var(--border-strong);
  background: var(--bg-elevated);
}

.quick-check summary {
  display: flex;
  min-height: 3.5rem;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4);
  cursor: pointer;
  font-weight: 700;
}

.quick-check summary > span {
  display: grid;
  flex: 0 0 auto;
  width: 2rem;
  height: 2rem;
  place-items: center;
  color: #fff;
  border-radius: 50%;
  background: #e8795d;
}

.quick-check[open] summary {
  border-bottom: 1px solid var(--border);
}

.quick-check > p,
.quick-check > ol {
  margin: 0;
  padding: var(--space-4);
}

.quick-check > ol {
  padding-left: 2.5rem;
}

.lesson-summary {
  padding: var(--space-5);
  border: 1px solid var(--border);
  background:
    linear-gradient(90deg, rgba(245, 158, 11, 0.09), transparent 60%),
    var(--bg-elevated);
}

.lesson-summary p {
  margin: var(--space-3) 0 0;
  color: var(--text-secondary);
  line-height: 1.75;
}

.lesson-side {
  display: grid;
  gap: var(--space-5);
}

.lesson-side section {
  padding: var(--space-4);
  border-top: 2px solid var(--border-strong);
}

.lesson-side h2 {
  margin: 0 0 var(--space-3);
  font-size: var(--fs-base);
}

.side-key-list {
  display: grid;
  gap: var(--space-3);
  margin: 0;
  padding: 0;
  color: var(--text-secondary);
  list-style: none;
  font-size: var(--fs-sm);
}

.side-key-list li {
  padding-bottom: var(--space-3);
  border-bottom: 1px solid var(--border);
}

.study-note {
  border: 1px solid #eadb9f !important;
  background:
    linear-gradient(rgba(211, 174, 58, 0.14) 1px, transparent 1px) 0 2.25rem / 100% 1.7rem,
    #fffbed;
}

.study-note p {
  min-height: 7rem;
  margin: 0;
  color: #554728;
  font-size: var(--fs-sm);
  line-height: 1.9;
}

[data-theme="dark"] .study-note {
  border-color: #7a6730 !important;
  background:
    linear-gradient(rgba(226, 194, 88, 0.12) 1px, transparent 1px) 0 2.25rem / 100% 1.7rem,
    #282414;
}

[data-theme="dark"] .study-note p {
  color: #f7e7a9;
}

.side-resource-link {
  display: inline-flex;
  min-height: var(--touch);
  align-items: center;
  font-weight: 700;
}

.lesson-actions {
  position: static;
  padding: var(--space-3);
  border: 1px solid var(--border);
  background: var(--bg-header);
  backdrop-filter: blur(12px);
}

@media (max-width: 639px) {
  :root {
    --header-h: 116px;
  }

  .site-header {
    height: calc(var(--header-h) + var(--sat));
  }

  .header-inner {
    height: var(--header-h);
    align-content: center;
    flex-wrap: wrap;
    padding-block: var(--space-2);
  }

  .brand {
    flex: 1 1 auto;
  }

  .brand-sub {
    display: none;
  }

  .header-actions {
    order: 2;
    width: 100%;
  }

  .header-actions .field {
    min-width: 0;
    flex: 1 1 0;
  }

  .header-actions .select {
    width: 100%;
    min-width: 0;
  }

  .field-label {
    display: none;
  }

  .home-hero {
    margin-inline: calc(-1 * var(--space-4));
  }

  .subject-rail {
    grid-template-columns: 1fr;
  }

  .lesson-actions .btn {
    flex: 1 1 100%;
  }
}

@media (min-width: 640px) {
  .home-hero {
    grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr);
    min-height: 35rem;
  }

  .home-hero-media {
    min-height: 100%;
  }

  .home-hero-media img {
    object-position: 58% center;
  }

  .home-section-head {
    flex-direction: row;
    align-items: center;
  }

  .subject-rail {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .learning-method > ol {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .home-progress {
    grid-template-columns: minmax(12rem, 1.6fr) repeat(3, minmax(6rem, 0.6fr)) auto;
  }

  .lesson-path {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .lesson-path li,
  .lesson-path li:nth-child(2n) {
    border-right: 1px solid var(--border);
    border-bottom: 0;
  }

  .lesson-path li:last-child {
    border-right: 0;
  }

  .solution-steps li {
    grid-template-columns: minmax(0, 1fr) minmax(10rem, 0.8fr);
    align-items: center;
  }
}

@media (min-width: 900px) {
  body {
    padding-bottom: var(--space-8);
  }

  .desktop-nav {
    display: flex;
    align-self: stretch;
    align-items: center;
  }

  .desktop-nav .nav-item {
    min-height: 100%;
    padding: 0 var(--space-3);
    color: var(--text-secondary);
    border-bottom: 3px solid transparent;
    font-size: var(--fs-sm);
    text-decoration: none;
  }

  .desktop-nav .nav-item.is-active {
    color: var(--primary);
    border-bottom-color: var(--primary);
  }

  .bottom-nav {
    display: none;
  }

  .lesson-layout {
    grid-template-columns: minmax(10.5rem, 0.55fr) minmax(0, 2.1fr) minmax(12.5rem, 0.7fr);
    gap: var(--space-6);
  }

  .lesson-toc,
  .lesson-side {
    position: sticky;
    top: calc(var(--header-h) + var(--space-6));
  }

  .lesson-visual-grid {
    grid-template-columns: minmax(0, 0.86fr) minmax(0, 1.14fr);
  }
}

@media (min-width: 1120px) {
  .subject-rail {
    grid-template-columns: repeat(9, minmax(0, 1fr));
  }

  .subject-rail-item {
    flex-direction: column;
    justify-content: center;
    text-align: center;
  }
}