/* ============================================================
   UPSKILLED PLATFORM — CSS
   Color system: dark = navy/steel-blue palette; light = pastel palette
   ============================================================ */


/* ----------------------------------------------------------
   1. THEME TOKENS
   ---------------------------------------------------------- */

[data-theme="dark"] {
  /* Brand palette — dark theme */
  --navy:          #1a3c75;
  --steel:         #1776a4;
  --sky:           #63aac9;
  --charcoal:      #191b1f;
  --teal:          #2a5757;

  /* Semantic surfaces */
  --bg:            #0f141a;
  --bg-nav:        #111827;
  --bg-surface:    #141c28;
  --bg-card:       #192236;
  --bg-card-hover: #1e2d47;
  --bg-elevated:   #1a3c75;

  /* Text */
  --text:          #dde8f4;
  --text-muted:    #8ab4cc;
  --text-faint:    #4d6f87;
  --text-on-accent:#ffffff;

  /* Accent */
  --accent:        #1776a4;
  --accent-hover:  #1e8ec0;
  --accent-light:  #63aac9;
  --accent-deep:   #1a3c75;
  --accent-teal:   #2a5757;

  /* Borders & shadows */
  --border:        rgba(99, 170, 201, 0.15);
  --border-strong: rgba(99, 170, 201, 0.35);
  --shadow-sm:     0 1px 3px rgba(0,0,0,0.4);
  --shadow-md:     0 4px 16px rgba(0,0,0,0.5);
  --shadow-lg:     0 8px 32px rgba(0,0,0,0.6);

  /* Code */
  --code-bg:       #0d1117;
  --code-text:     #63aac9;

  /* Syntax highlighting (hljs) */
  --hljs-base:     #c9d1d9;
  --hljs-kw:       #b1aad1;
  --hljs-builtin:  #63aac9;
  --hljs-string:   #52ab97;
  --hljs-number:   #fbbf24;
  --hljs-comment:  #4d6f87;
  --hljs-fn:       #63aac9;
  --hljs-class:    #8ab4cc;
  --hljs-meta:     #fbbf24;
  --hljs-attr:     #8ab4cc;

  /* Progress */
  --progress-bg:   rgba(99,170,201,0.12);
  --progress-fill: #1776a4;

  /* Semantic state colors */
  --success:       #22c55e;
  --success-bg:    rgba(34, 197, 94, 0.08);
  --danger:        #ef4444;
  --danger-bg:     rgba(239, 68, 68, 0.08);
  --warn:          #f59e0b;
  --warn-bg:       rgba(245, 158, 11, 0.1);

  /* Nav */
  --nav-height:    60px;
}

[data-theme="light"] {
  /* Brand palette — light theme */
  --navy:          #1a3c75;
  --steel:         #1776a4;
  --sky:           #63aac9;
  --charcoal:      #191b1f;
  --teal:          #2a5757;

  /* Pastel palette */
  --blue-soft:     #c8d9f0;
  --pink-soft:     #edced3;
  --mauve-soft:    #d9c2d6;
  --lavender-pale: #f4eef3;
  --purple-mid:    #b1aad1;

  /* Semantic surfaces */
  --bg:            #f4eef3;
  --bg-nav:        #ffffff;
  --bg-surface:    #ffffff;
  --bg-card:       #ffffff;
  --bg-card-hover: #f0e8ef;
  --bg-elevated:   #edced3;

  /* Text */
  --text:          #1e1a2a;
  --text-muted:    #5a5270;
  --text-faint:    #9b92af;
  --text-on-accent:#ffffff;

  /* Accent */
  --accent:        #b1aad1;
  --accent-hover:  #9e96c2;
  --accent-light:  #c8d9f0;
  --accent-deep:   #1776a4;
  --accent-teal:   #2a5757;

  /* Borders & shadows */
  --border:        rgba(177, 170, 209, 0.3);
  --border-strong: rgba(177, 170, 209, 0.6);
  --shadow-sm:     0 1px 3px rgba(26,60,117,0.08);
  --shadow-md:     0 4px 16px rgba(26,60,117,0.12);
  --shadow-lg:     0 8px 32px rgba(26,60,117,0.16);

  /* Code */
  --code-bg:       #f0ebf4;
  --code-text:     #1776a4;

  /* Syntax highlighting (hljs) */
  --hljs-base:     #1e1a2a;
  --hljs-kw:       #7c3aed;
  --hljs-builtin:  #1776a4;
  --hljs-string:   #0d7490;
  --hljs-number:   #b45309;
  --hljs-comment:  #9b92af;
  --hljs-fn:       #1776a4;
  --hljs-class:    #2a5757;
  --hljs-meta:     #b45309;
  --hljs-attr:     #1776a4;

  /* Progress */
  --progress-bg:   rgba(177,170,209,0.2);
  --progress-fill: #b1aad1;

  /* Semantic state colors */
  --success:       #16a34a;
  --success-bg:    rgba(22, 163, 74, 0.08);
  --danger:        #dc2626;
  --danger-bg:     rgba(220, 38, 38, 0.08);
  --warn:          #d97706;
  --warn-bg:       rgba(217, 119, 6, 0.1);

  /* Nav */
  --nav-height:    60px;
}

/* ----------------------------------------------------------
   2. RESET & BASE
   ---------------------------------------------------------- */

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background 0.25s, color 0.25s;
  line-height: 1.6;
}

a { color: var(--accent-deep); text-decoration: none; }
a:hover { text-decoration: underline; }
[data-theme="dark"] a { color: var(--sky); }

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

/* ----------------------------------------------------------
   3. NAV
   ---------------------------------------------------------- */

.platform-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-height);
  background: var(--bg-nav);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
}

.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  gap: 16px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  flex-shrink: 0;
}
.nav-brand:hover { text-decoration: none; }

.brand-logo {
  height: 32px;
  width: auto;
  display: block;
  flex-shrink: 0;
}

.nav-breadcrumb {
  flex: 1;
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.83rem;
  color: var(--text-muted);
  overflow: hidden;
  white-space: nowrap;
}

.nav-breadcrumb a {
  color: var(--text-muted);
  text-decoration: none;
}
.nav-breadcrumb a:hover { color: var(--accent-light); text-decoration: underline; }
.nav-breadcrumb .bc-sep { opacity: 0.4; }
.nav-breadcrumb .bc-current { color: var(--text); font-weight: 500; overflow: hidden; text-overflow: ellipsis; }

.nav-actions { display: flex; align-items: center; gap: 8px; margin-left: auto; flex-shrink: 0; }

.theme-toggle {
  position: relative;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.theme-toggle:hover {
  background: var(--bg-card-hover);
  color: var(--text);
  border-color: var(--border-strong);
}
/* Both icons always in DOM — morph via opacity + rotation */
.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  position: absolute;
  transition: opacity 0.3s ease, transform 0.3s ease;
}
/* Dark mode: moon visible, sun rotated away */
.theme-toggle .icon-sun  { opacity: 0; transform: scale(0.5) rotate(90deg); }
.theme-toggle .icon-moon { opacity: 1; transform: scale(1)   rotate(0deg); }
/* Light mode: sun visible, moon rotated away */
[data-theme="light"] .theme-toggle .icon-sun  { opacity: 1; transform: scale(1)   rotate(0deg); }
[data-theme="light"] .theme-toggle .icon-moon { opacity: 0; transform: scale(0.5) rotate(-90deg); }
@media (prefers-reduced-motion: reduce) {
  .theme-toggle .icon-sun,
  .theme-toggle .icon-moon { transition: none; }
}

/* ----------------------------------------------------------
   4. MAIN & FOOTER
   ---------------------------------------------------------- */

#appRoot {
  flex: 1;
  min-height: 0;
}

.platform-footer {
  border-top: 1px solid var(--border);
  background: var(--bg-nav);
  margin-top: auto;
  padding: 48px 24px 0;
}

.footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 56px;
  padding-bottom: 40px;
}

/* Brand column */
.footer-brand {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.footer-logo-link {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: rgba(100, 200, 180, 1);
  text-decoration: none;
  opacity: 0.8;
  transition: opacity 0.2s;
}
.footer-logo-link:hover { opacity: 1; }

.footer-tagline {
  font-size: 0.78rem;
  color: var(--text-faint);
  letter-spacing: 0.02em;
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 20px;
}

.footer-nav a {
  font-size: 0.78rem;
  color: rgba(100, 200, 180, 0.75);
  text-decoration: none;
  transition: color 0.2s;
}
.footer-nav a:hover { color: rgba(100, 200, 180, 1); }

.footer-copy {
  font-size: 0.75rem;
  color: var(--text-faint);
  margin-top: 4px;
}
.footer-copy a { color: rgba(100, 200, 180, 0.75); text-decoration: none; }
.footer-copy a:hover { color: rgba(100, 200, 180, 1); }

/* Contact column */
.footer-contact-heading {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 6px;
  text-transform: uppercase;
}

.footer-contact-sub {
  font-size: 0.8rem;
  line-height: 1.7;
  color: var(--text-faint);
  margin-bottom: 16px;
}

.footer-form-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.footer-form-row input {
  flex: 1;
  min-width: 100px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 12px;
  font-family: inherit;
  font-size: 0.8rem;
  color: var(--text);
  outline: none;
  transition: border-color 0.2s;
}
.footer-form-row input::placeholder { color: var(--text-faint); }
.footer-form-row input:focus { border-color: var(--border-strong); }

.footer-submit-btn {
  background: var(--accent);
  border: none;
  border-radius: 6px;
  padding: 8px 18px;
  font-family: inherit;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-on-accent);
  cursor: pointer;
  transition: background 0.2s;
  white-space: nowrap;
}
.footer-submit-btn:hover { background: var(--accent-hover); }
.footer-submit-btn:disabled { opacity: 0.5; cursor: not-allowed; }

#footer-form-message .message {
  font-size: 0.78rem;
  padding: 7px 12px;
  border-radius: 6px;
  margin-bottom: 12px;
}
#footer-form-message .message.success {
  color: var(--success);
  background: var(--success-bg);
}
#footer-form-message .message.error {
  color: var(--danger);
  background: var(--danger-bg);
}

@media (max-width: 640px) {
  .platform-footer {
    padding-bottom: 80px;
  }
  .footer-inner {
    grid-template-columns: 1fr;
    gap: 32px;
  }
}

/* ----------------------------------------------------------
   5. CATALOG VIEW
   ---------------------------------------------------------- */

.catalog-hero {
  background: linear-gradient(160deg, var(--bg-surface) 0%, var(--bg) 100%);
  border-bottom: 1px solid var(--border);
  padding: 56px 24px 48px;
}

[data-theme="dark"] .catalog-hero {
  background: linear-gradient(160deg, #141c28 0%, #0f141a 60%, #111d2e 100%);
}

.catalog-hero-inner {
  max-width: 780px;
  margin: 0 auto;
}

.catalog-hero-inner h1 {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1.15;
  color: var(--text);
  margin-bottom: 14px;
}

.catalog-hero-inner h1 .hero-accent {
  background: linear-gradient(90deg, #52ab97 0%, #2a6585 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* "& Training" — clip-path wipe, outside the gradient span to avoid
   background-clip:text conflicts */
.catalog-hero-inner h1 .hero-suffix {
  display: inline-block;
  color: #52ab97;
  padding-bottom: 0.15em;
  clip-path: inset(0 100% 0 0);
  animation: heroSuffixReveal 0.7s cubic-bezier(0.22, 1, 0.36, 1) 0.5s forwards;
}

[data-theme="light"] .catalog-hero-inner h1 .hero-suffix {
  color: #2a6585;
}

@keyframes heroSuffixReveal {
  to { clip-path: inset(0 0% 0 0); }
}

.catalog-hero-inner p {
  font-size: 1.05rem;
  color: var(--text-muted);
  max-width: 560px;
  line-height: 1.65;
}

/* Catalog body */
.catalog-body {
  max-width: 1200px;
  margin: 0 auto;
  padding: 48px 24px 80px;
}

.catalog-section { margin-bottom: 56px; }
.catalog-section:last-child { margin-bottom: 0; }

.section-header {
  margin-bottom: 24px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: baseline;
  gap: 12px;
}

.section-header h2 {
  font-size: 1.2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}

.section-header p {
  font-size: 0.85rem;
  color: var(--text-muted);
  flex: 1;
}

/* Course grid */
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 20px;
}

.course-grid.featured-grid {
  grid-template-columns: repeat(auto-fill, minmax(440px, 1fr));
}

/* Course card */
.course-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  cursor: pointer;
  transition: transform 0.18s, box-shadow 0.18s, border-color 0.18s;
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
}

.course-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--border-strong);
  text-decoration: none;
  color: inherit;
}

.course-card-stripe {
  height: 4px;
  width: 100%;
}

.course-card-body {
  padding: 22px 22px 18px;
  flex: 1;
  display: flex;
  flex-direction: column;
}

.course-card-type {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  margin-bottom: 8px;
}

.course-card-title {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.3;
  color: var(--text);
  margin-bottom: 10px;
}

.course-card-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.6;
  flex: 1;
  margin-bottom: 16px;
}

.course-card-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 14px;
}

.meta-pill {
  font-size: 0.72rem;
  font-weight: 600;
  padding: 3px 9px;
  border-radius: 20px;
  background: var(--bg-elevated);
  color: var(--text-muted);
  border: 1px solid var(--border);
}

.meta-pill.level-foundational { background: rgba(23,118,164,0.12); color: var(--sky); border-color: rgba(23,118,164,0.25); }
.meta-pill.level-advanced { background: rgba(26,60,117,0.15); color: var(--sky); border-color: rgba(26,60,117,0.3); }

[data-theme="light"] .meta-pill.level-foundational { background: rgba(99,170,201,0.15); color: var(--steel); border-color: rgba(99,170,201,0.35); }
[data-theme="light"] .meta-pill.level-advanced { background: rgba(177,170,209,0.2); color: #6b62a0; border-color: rgba(177,170,209,0.4); }

.course-card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.tag-chip {
  font-size: 0.69rem;
  padding: 2px 8px;
  border-radius: 4px;
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-faint);
}

.course-card-footer {
  padding: 14px 22px;
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.card-cta {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent-light);
  display: flex;
  align-items: center;
  gap: 5px;
}

[data-theme="light"] .card-cta { color: var(--steel); }

.card-cta-arrow {
  font-size: 0.9rem;
  transition: transform 0.15s;
}

.course-card:hover .card-cta-arrow { transform: translateX(3px); }

/* ----------------------------------------------------------
   6. COURSE OVERVIEW (prereq module page)
   ---------------------------------------------------------- */

.course-overview {
  max-width: 860px;
  margin: 0 auto;
  padding: 40px 24px 80px;
}

.course-ov-header {
  margin-bottom: 36px;
}

.course-ov-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 20px;
  cursor: pointer;
  background: none;
  border: none;
  padding: 0;
}
.course-ov-back:hover { color: var(--text); }

.course-ov-kicker {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  margin-bottom: 8px;
}

.course-ov-title {
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.2;
  color: var(--text);
  margin-bottom: 12px;
}

.course-ov-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.65;
  max-width: 640px;
  margin-bottom: 20px;
}

.course-ov-meta { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 0; }

/* Reading list */
.reading-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
  margin-top: 8px;
}

.reading-list-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-faint);
  margin-bottom: 10px;
  margin-top: 32px;
}

.reading-row {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 18px;
  border-radius: 10px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: background 0.14s, border-color 0.14s;
  text-decoration: none;
  color: inherit;
}

.reading-row:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-strong);
  text-decoration: none;
  color: inherit;
}

.reading-row-num {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-muted);
  flex-shrink: 0;
}

.reading-row-info { flex: 1; min-width: 0; }

.reading-row-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.35;
  margin-bottom: 3px;
}

.reading-row-desc {
  font-size: 0.78rem;
  color: var(--text-faint);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.reading-row-time {
  font-size: 0.75rem;
  color: var(--text-faint);
  flex-shrink: 0;
}

.reading-row-done {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: #22c55e22;
  border: 1.5px solid #22c55e66;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.65rem;
  color: #22c55e;
  flex-shrink: 0;
}

/* ----------------------------------------------------------
   7. READING VIEW
   ---------------------------------------------------------- */

.reading-layout {
  display: flex;
  gap: 0;
  min-height: calc(100vh - var(--nav-height));
}

/* Sidebar */
.reading-sidebar {
  width: 240px;
  flex-shrink: 0;
  border-right: 1px solid var(--border);
  background: var(--bg-surface);
  padding: 24px 0;
  position: sticky;
  top: var(--nav-height);
  height: calc(100vh - var(--nav-height));
  overflow-y: auto;
  display: flex;
  flex-direction: column;
}

.sidebar-course-link {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 16px 16px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 12px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  background: none;
  border-left: none;
  border-right: none;
  border-top: none;
  text-align: left;
}
.sidebar-course-link:hover { color: var(--text); }

.sidebar-nav-label {
  font-size: 0.67rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  padding: 0 16px 6px;
}

.sidebar-reading-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 16px;
  font-size: 0.82rem;
  color: var(--text-muted);
  cursor: pointer;
  background: none;
  border: none;
  text-align: left;
  width: 100%;
  transition: background 0.12s, color 0.12s;
  border-left: 3px solid transparent;
  line-height: 1.35;
}
.sidebar-reading-item:hover { background: var(--bg-card-hover); color: var(--text); }
.sidebar-reading-item.active {
  color: var(--text);
  font-weight: 600;
  border-left-color: var(--accent);
  background: var(--bg-card);
}

[data-theme="light"] .sidebar-reading-item.active { border-left-color: var(--steel); }

.sidebar-item-num {
  font-size: 0.68rem;
  width: 18px;
  color: var(--text-faint);
  flex-shrink: 0;
  text-align: right;
}

/* Reading main area */
.reading-main {
  flex: 1;
  min-width: 0;
  padding: 40px 56px 80px 48px;
  max-width: 760px;
}

.reading-kicker {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  margin-bottom: 8px;
}

.reading-title {
  font-size: clamp(1.4rem, 2.5vw, 1.85rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.2;
  color: var(--text);
  margin-bottom: 6px;
}

.reading-meta-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 32px;
  font-size: 0.78rem;
  color: var(--text-faint);
}

.reading-meta-sep { opacity: 0.4; }

/* Learning objectives block */
.reading-los {
  border-left: 3px solid var(--accent-light);
  background: color-mix(in srgb, var(--accent-light) 6%, transparent);
  border-radius: 0 8px 8px 0;
  padding: 14px 18px;
  margin-bottom: 32px;
}
.reading-los-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-light);
  margin-bottom: 8px;
}
.reading-los-list {
  margin: 0;
  padding-left: 1.1em;
  list-style: disc;
}
.reading-los-list li {
  font-size: 0.88rem;
  line-height: 1.55;
  color: var(--text-muted);
  margin: 4px 0;
}
.reading-los-list li strong {
  color: var(--text);
  font-weight: 600;
}

/* Markdown content */
.reading-content {
  font-size: 0.95rem;
  line-height: 1.75;
  color: var(--text);
}

.reading-content h2 {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
  margin: 2.2rem 0 0.8rem;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

.reading-content h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text);
  margin: 1.6rem 0 0.6rem;
}

.reading-content h4 {
  font-size: 0.9rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin: 1.4rem 0 0.5rem;
}

.reading-content p { margin-bottom: 1rem; }

.reading-content ul, .reading-content ol {
  padding-left: 1.4em;
  margin-bottom: 1rem;
}
.reading-content li { margin-bottom: 0.35rem; }

.reading-content strong { font-weight: 700; color: var(--text); }
.reading-content em { font-style: italic; }

.reading-content code {
  font-family: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
  font-size: 0.82em;
  background: var(--code-bg);
  /* no color here — inline vs block code differ, see rules below */
  padding: 1px 5px;
  border-radius: 4px;
  border: 1px solid var(--border);
}

/* Inline code only (not inside <pre>) */
.reading-content :not(pre) > code {
  color: var(--code-text);
}

.reading-content pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px 18px;
  overflow-x: auto;
  margin: 1rem 0 2rem;
}
.reading-content pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.83em;
  /* color comes from .hljs via CSS vars below */
}

.reading-content blockquote {
  border-left: 3px solid var(--accent);
  padding: 10px 16px;
  margin: 1rem 0;
  background: var(--bg-card);
  border-radius: 0 8px 8px 0;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.reading-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0;
  font-size: 0.85rem;
}
.reading-content th, .reading-content td {
  padding: 8px 12px;
  border: 1px solid var(--border);
  text-align: left;
}
.reading-content th {
  background: var(--bg-elevated);
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
}
.reading-content tr:nth-child(even) { background: var(--bg-card); }

/* Display math */
.reading-content .katex-display {
  margin: 1.4rem 0;
  overflow-x: auto;
  padding: 4px 0 8px;
}

/* Equation breakdown cards */
.eq-breakdown {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  margin: 1.6rem 0;
}

.eq-breakdown-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--text-faint);
  margin-bottom: 14px;
}

.eq-term {
  display: grid;
  grid-template-columns: 7.5rem 1fr;
  gap: 4px 28px;
  align-items: start;
  padding: 10px 0;
  border-top: 1px solid var(--border);
}
.eq-term:first-of-type { border-top: none; }

.eq-symbol {
  font-size: 0.9rem;
  color: var(--accent-light);
  white-space: nowrap;
  padding-top: 3px;
  overflow: hidden;
  text-overflow: ellipsis;
}
[data-theme="light"] .eq-symbol { color: var(--steel); }

.eq-name {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 3px;
}

.eq-desc {
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.6;
}

/* Reading nav buttons */
.reading-nav-row {
  display: flex;
  justify-content: space-between;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  gap: 12px;
}

.reading-nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.83rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.reading-nav-btn:hover {
  background: var(--bg-card-hover);
  color: var(--text);
  border-color: var(--border-strong);
}
.reading-nav-btn.next {
  margin-left: auto;
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.reading-nav-btn.next:hover { background: var(--accent-hover); border-color: var(--accent-hover); }

/* References */
.references-section {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}
.references-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--text-faint);
  margin-bottom: 12px;
}
.reference-item {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 6px;
  padding-left: 1em;
  position: relative;
}
.reference-item::before {
  content: "–";
  position: absolute;
  left: 0;
  color: var(--text-faint);
}

/* ----------------------------------------------------------
   8. NOTATION & GREEK TABLE (r0 reference page)
   ---------------------------------------------------------- */

.notation-table-wrap {
  overflow-x: auto;
  margin: 1.4rem 0;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg-card);
}

.notation-table {
  border-collapse: collapse;
  width: 100%;
}

.notation-table tbody tr {
  transition: background 0.1s;
}

.notation-table tbody tr:hover td {
  background: var(--bg-card-hover);
}

.notation-table tbody tr + tr td {
  border-top: 1px solid var(--border);
}

.nt-symbol {
  text-align: right;
  width: 44%;
  padding: 9px 18px 9px 14px;
  border-right: 2px solid var(--border-strong);
  font-size: 0.9rem;
  white-space: nowrap;
  vertical-align: middle;
}

.nt-desc {
  text-align: left;
  padding: 9px 14px 9px 18px;
  font-size: 0.85rem;
  color: var(--text-muted);
  vertical-align: middle;
  line-height: 1.5;
}

/* Greek letters table */
.greek-table-wrap {
  overflow-x: auto;
  margin: 1.4rem 0 0.4rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg-card);
}

.greek-table {
  border-collapse: collapse;
  width: 100%;
}

.greek-table thead th {
  padding: 8px 12px;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-faint);
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  text-align: left;
}

.greek-table th:nth-child(1),
.greek-table th:nth-child(3) {
  text-align: center;
  width: 80px;
}

.greek-table tbody tr + tr td {
  border-top: 1px solid var(--border);
}

.greek-table tbody tr:hover td {
  background: var(--bg-card-hover);
}

.greek-table tbody tr td:nth-child(2) {
  border-right: 1px solid var(--border-strong);
  padding-right: 20px;
}

.greek-table tbody tr td:nth-child(3) {
  padding-left: 20px;
}

.gr-char {
  text-align: center;
  padding: 8px 12px;
  font-size: 1.05rem;
  vertical-align: middle;
  width: 80px;
}

.gr-name {
  padding: 8px 12px;
  font-size: 0.85rem;
  color: var(--text);
  vertical-align: middle;
  white-space: nowrap;
}

.gr-name em {
  font-style: italic;
  color: var(--text-faint);
  font-size: 0.82em;
  margin-left: 4px;
}

.greek-note {
  font-size: 0.78rem;
  color: var(--text-faint);
  text-align: center;
  padding: 8px 14px 10px;
  margin: 0 !important;
  border-top: 1px solid var(--border);
}

/* ----------------------------------------------------------
   9. QUIZ VIEW
   ---------------------------------------------------------- */

.quiz-question-list {
  display: flex;
  flex-direction: column;
  gap: 24px;
  margin-top: 8px;
  margin-bottom: 32px;
}

/* Question card */
.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 22px 24px;
  transition: border-color 0.2s;
}

.question-card.answered-correct { border-color: var(--success); }
.question-card.answered-wrong   { border-color: var(--danger); }

.question-num {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  margin-bottom: 10px;
}

.question-prompt {
  font-size: 0.93rem;
  font-weight: 600;
  line-height: 1.6;
  color: var(--text);
  margin-bottom: 18px;
}

/* Multiple choice — label + radio */
.options-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.option-label {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 11px 14px;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.88rem;
  line-height: 1.55;
  transition: border-color 0.12s, background 0.12s;
}

.option-label:hover:not(.disabled) {
  border-color: var(--accent);
  background: var(--bg-card-hover);
}

.option-label input[type="radio"] {
  flex-shrink: 0;
  margin-top: 3px;
  accent-color: var(--accent);
  width: 16px;
  height: 16px;
}

.option-label.selected {
  border-color: var(--accent);
  background: var(--bg-card-hover);
}

.option-label.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.option-label.wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
}

.option-label.disabled { cursor: default; }

/* Submitted state: suppress hover on non-result options */
.quiz-submitted .option-label { cursor: default; }
.quiz-submitted .option-label:hover:not(.correct):not(.wrong):not(.selected) {
  border-color: var(--border);
  background: none;
}

/* Code completion */
.code-template-wrap { margin-bottom: 4px; }

.code-template {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px 16px;
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
  font-size: 0.82em;
  color: var(--text-muted);
  white-space: pre;
  overflow-x: auto;
  line-height: 1.65;
}

.code-blank-input {
  display: inline-block;
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
  font-size: 1em;
  background: rgba(23, 118, 164, 0.18);
  border: 1.5px solid var(--accent);
  border-radius: 4px;
  padding: 0 7px;
  color: var(--text);
  outline: none;
  min-width: 90px;
  transition: border-color 0.12s, background 0.12s;
  vertical-align: baseline;
}

.code-blank-input:focus {
  border-color: var(--accent-light);
  background: rgba(23, 118, 164, 0.28);
}

.code-blank-input.correct {
  border-color: var(--success);
  background: var(--success-bg);
  color: var(--success);
}

.code-blank-input.wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
  color: var(--danger);
}

/* Hint toggle */
.hint-toggle {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 16px;
  padding: 5px 13px 5px 10px;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--warn);
  background: var(--warn-bg);
  border: 1.5px solid rgba(245, 158, 11, 0.3);
  border-radius: 999px;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, box-shadow 0.15s;
}

.hint-toggle:hover {
  background: rgba(245, 158, 11, 0.18);
  border-color: var(--warn);
  box-shadow: 0 0 0 3px rgba(245, 158, 11, 0.1);
}

.hint-toggle:disabled { opacity: 0.4; cursor: default; box-shadow: none; }
.hint-toggle svg { flex-shrink: 0; }
.hint-toggle.hint-open svg.icon-bulb  { display: none; }
.hint-toggle:not(.hint-open) svg.icon-close { display: none; }

/* Hint content */
.question-hint {
  margin-top: 12px;
  padding: 10px 14px;
  background: var(--warn-bg);
  border-left: 3px solid var(--warn);
  border-radius: 0 8px 8px 0;
  font-size: 0.83rem;
  color: var(--text-muted);
  line-height: 1.6;
  display: none;
}

.question-hint.visible { display: block; }

/* Explanation (shown after submit) */
.question-explanation {
  margin-top: 12px;
  padding: 12px 14px;
  background: var(--bg-elevated);
  border-left: 3px solid var(--border-strong);
  border-radius: 0 8px 8px 0;
  font-size: 0.83rem;
  color: var(--text-muted);
  line-height: 1.6;
  display: none;
}

.question-explanation.visible { display: block; }
.question-explanation strong { color: var(--text); }

/* Submit button */
.quiz-actions {
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.quiz-submit-btn {
  padding: 11px 28px;
  border-radius: 8px;
  background: var(--accent);
  border: none;
  color: #fff;
  font-size: 0.9rem;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.15s;
}

.quiz-submit-btn:hover { background: var(--accent-hover); }

/* Score card */
.quiz-score-card {
  border-radius: 14px;
  padding: 32px 28px 28px;
  border: 1.5px solid var(--border);
  background: var(--bg-card);
  text-align: center;
  margin-top: 28px;
}

.quiz-score-card.passed { border-color: var(--success); background: var(--success-bg); }
.quiz-score-card.failed { border-color: var(--danger); background: var(--danger-bg); }

.quiz-score-pct {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1;
  margin-bottom: 8px;
}

.quiz-score-card.passed .quiz-score-pct { color: var(--success); }
.quiz-score-card.failed .quiz-score-pct { color: var(--danger); }

.quiz-score-label {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: 22px;
  line-height: 1.6;
}

.quiz-result-actions {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
}

.quiz-retry-btn {
  padding: 9px 22px;
  border-radius: 8px;
  background: var(--bg-elevated);
  border: 1.5px solid var(--border);
  color: var(--text-muted);
  font-size: 0.86rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.14s;
}

.quiz-retry-btn:hover { background: var(--bg-card-hover); color: var(--text); border-color: var(--border-strong); }

/* Quiz row in course overview */
.quiz-row {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 18px;
  border-radius: 10px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: background 0.14s, border-color 0.14s;
}

.quiz-row:hover { background: var(--bg-card-hover); border-color: var(--border-strong); }

.quiz-row-icon {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  background: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.65rem;
  font-weight: 800;
  color: #fff;
  flex-shrink: 0;
  letter-spacing: 0.02em;
  font-family: 'JetBrains Mono', monospace;
}

[data-theme="light"] .quiz-row-icon { background: var(--steel); }

.quiz-row-info { flex: 1; min-width: 0; }
.quiz-row-title { font-size: 0.9rem; font-weight: 600; color: var(--text); line-height: 1.35; margin-bottom: 3px; }
.quiz-row-desc { font-size: 0.78rem; color: var(--text-faint); }

.quiz-row-passed {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--success-bg);
  border: 1.5px solid rgba(34, 197, 94, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.65rem;
  color: var(--success);
  flex-shrink: 0;
}

/* Sidebar quiz item */
.sidebar-quiz-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 16px;
  font-size: 0.82rem;
  color: var(--text-muted);
  cursor: pointer;
  background: none;
  border: none;
  text-align: left;
  width: 100%;
  transition: background 0.12s, color 0.12s;
  border-left: 3px solid transparent;
  line-height: 1.35;
}

.sidebar-quiz-item:hover { background: var(--bg-card-hover); color: var(--text); }

.sidebar-quiz-item.active {
  color: var(--text);
  font-weight: 600;
  border-left-color: var(--accent);
  background: var(--bg-card);
}

[data-theme="light"] .sidebar-quiz-item.active { border-left-color: var(--steel); }

.sidebar-quiz-icon {
  font-size: 0.6rem;
  font-weight: 800;
  width: 18px;
  height: 18px;
  border-radius: 4px;
  background: var(--accent);
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-family: 'JetBrains Mono', monospace;
}

[data-theme="light"] .sidebar-quiz-icon { background: var(--steel); }

/* ----------------------------------------------------------
   10. LAB VIEW
   ---------------------------------------------------------- */

/* Colab launch card */
.lab-colab-card {
  background: linear-gradient(135deg, #f97316, #f59e0b);
  border-radius: 14px;
  padding: 24px 28px;
  margin-bottom: 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
}

.lab-colab-info { flex: 1; min-width: 0; }

.lab-colab-kicker {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: rgba(255,255,255,0.8);
  margin-bottom: 4px;
}

.lab-colab-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: #fff;
  line-height: 1.3;
  margin-bottom: 4px;
}

.lab-colab-meta {
  font-size: 0.8rem;
  color: rgba(255,255,255,0.75);
}

.lab-colab-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: 8px;
  background: #fff;
  color: #f97316;
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
  flex-shrink: 0;
  transition: opacity 0.15s, transform 0.1s;
  border: none;
  cursor: pointer;
}

.lab-colab-btn:hover { opacity: 0.9; transform: translateY(-1px); }
.lab-colab-btn:active { transform: translateY(0); }

/* Objectives card */
.lab-objectives {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px 22px;
  margin-bottom: 32px;
}

.lab-objectives-label {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  margin-bottom: 14px;
}

.lab-objective-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 10px 0;
  border-top: 1px solid var(--border);
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.6;
}

.lab-objective-item:first-of-type { border-top: none; padding-top: 0; }

.lab-objective-num {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--success-bg);
  border: 1.5px solid rgba(34, 197, 94, 0.35);
  color: var(--success);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.65rem;
  font-weight: 700;
  flex-shrink: 0;
  margin-top: 1px;
}

/* Lab row in course overview */
.lab-row {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 18px;
  border-radius: 10px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: background 0.14s, border-color 0.14s;
}

.lab-row:hover { background: var(--bg-card-hover); border-color: var(--border-strong); }

.lab-row-icon {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  background: linear-gradient(135deg, #f97316, #f59e0b);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.lab-row-icon svg { width: 14px; height: 14px; color: #fff; stroke: #fff; }

.lab-row-info { flex: 1; min-width: 0; }
.lab-row-title { font-size: 0.9rem; font-weight: 600; color: var(--text); line-height: 1.35; margin-bottom: 3px; }
.lab-row-desc { font-size: 0.78rem; color: var(--text-faint); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.lab-row-time { font-size: 0.75rem; color: var(--text-faint); flex-shrink: 0; }

.lab-row-visited {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: rgba(249, 115, 22, 0.1);
  border: 1.5px solid rgba(249, 115, 22, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.65rem;
  color: #f97316;
  flex-shrink: 0;
}

/* Sidebar lab item */
.sidebar-lab-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 16px;
  font-size: 0.82rem;
  color: var(--text-muted);
  cursor: pointer;
  background: none;
  border: none;
  text-align: left;
  width: 100%;
  transition: background 0.12s, color 0.12s;
  border-left: 3px solid transparent;
  line-height: 1.35;
}

.sidebar-lab-item:hover { background: var(--bg-card-hover); color: var(--text); }

.sidebar-lab-item.active {
  color: var(--text);
  font-weight: 600;
  border-left-color: #f97316;
  background: var(--bg-card);
}

.sidebar-lab-icon {
  width: 18px;
  height: 18px;
  border-radius: 4px;
  background: linear-gradient(135deg, #f97316, #f59e0b);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.sidebar-lab-icon svg { width: 10px; height: 10px; stroke: #fff; }

/* ----------------------------------------------------------
   11. LOADING & ERROR
   ---------------------------------------------------------- */

.loading-state {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 240px;
  flex-direction: column;
  gap: 14px;
  color: var(--text-faint);
  font-size: 0.85rem;
}

.spinner {
  width: 32px;
  height: 32px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

.error-state {
  padding: 48px 24px;
  text-align: center;
  color: var(--text-muted);
}

.error-state h2 {
  font-size: 1.1rem;
  margin-bottom: 8px;
  color: var(--text);
}

/* ----------------------------------------------------------
   12. RESPONSIVE
   ---------------------------------------------------------- */

@media (max-width: 900px) {
  .reading-sidebar { display: none; }
  .reading-main { padding: 28px 24px 60px; }
}

@media (max-width: 720px) {
  .catalog-hero { padding: 36px 16px 32px; }
  .catalog-body { padding: 32px 16px 60px; }
  .course-grid, .course-grid.featured-grid {
    grid-template-columns: 1fr;
  }
  .section-header { flex-direction: column; align-items: flex-start; gap: 4px; }
  .reading-main { padding: 20px 16px 48px; }
}

/* ----------------------------------------------------------
   13. SCROLLBAR (dark theme)
   ---------------------------------------------------------- */

[data-theme="dark"] ::-webkit-scrollbar { width: 6px; height: 6px; }
[data-theme="dark"] ::-webkit-scrollbar-track { background: var(--bg); }
[data-theme="dark"] ::-webkit-scrollbar-thumb { background: #2a3a50; border-radius: 3px; }
[data-theme="dark"] ::-webkit-scrollbar-thumb:hover { background: var(--steel); }

/* ----------------------------------------------------------
   14. SEARCH — NAV PILL
   ---------------------------------------------------------- */

.nav-search {
  flex-shrink: 0;
}

.search-pill {
  display: flex;
  align-items: center;
  gap: 7px;
  height: 34px;
  padding: 0 11px;
  border-radius: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-faint);
  cursor: pointer;
  font-size: 0.82rem;
  transition: border-color 0.15s, background 0.15s, color 0.15s;
  white-space: nowrap;
}
.search-pill:hover {
  border-color: var(--border-strong);
  background: var(--bg-card-hover);
  color: var(--text-muted);
}
.search-pill svg { flex-shrink: 0; opacity: 0.7; }

.search-pill-hint {
  color: var(--text-faint);
  min-width: 56px;
}

.search-pill-kbd {
  font-size: 0.72rem;
  padding: 2px 5px;
  border-radius: 4px;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-faint);
  letter-spacing: 0;
  line-height: 1.5;
}

/* On Windows/Linux show Ctrl+K instead of ⌘K (JS swaps this) */

/* ----------------------------------------------------------
   14b. SEARCH — OVERLAY & MODAL
   ---------------------------------------------------------- */

.search-overlay {
  position: fixed;
  inset: 0;
  z-index: 300;
  background: rgba(0, 0, 0, 0.55);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding-top: 80px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.18s ease;
}
.search-overlay.is-open {
  opacity: 1;
  pointer-events: auto;
}

.search-modal {
  width: min(620px, calc(100vw - 32px));
  max-height: calc(100vh - 120px);
  background: var(--bg-card);
  border: 1px solid var(--border-strong);
  border-radius: 14px;
  box-shadow: var(--shadow-lg), 0 0 0 1px rgba(255,255,255,0.04);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  transform: translateY(-6px);
  transition: transform 0.18s ease;
}
.search-overlay.is-open .search-modal {
  transform: translateY(0);
}

.search-modal-head {
  padding: 14px 16px 10px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.search-input-row {
  display: flex;
  align-items: center;
  gap: 10px;
}
.search-input-row svg { flex-shrink: 0; opacity: 0.5; color: var(--text-muted); }

.search-field {
  flex: 1;
  min-width: 0;
  background: transparent;
  border: none;
  outline: none;
  font-size: 1rem;
  color: var(--text);
  caret-color: var(--accent-light);
  font-family: inherit;
}
.search-field::placeholder { color: var(--text-faint); }

.search-esc-btn {
  font-size: 0.7rem;
  padding: 3px 7px;
  border-radius: 4px;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-faint);
  cursor: pointer;
  flex-shrink: 0;
  font-family: inherit;
  transition: border-color 0.12s, color 0.12s;
}
.search-esc-btn:hover { border-color: var(--border-strong); color: var(--text-muted); }

.search-scope-bar {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-top: 8px;
  font-size: 0.76rem;
  color: var(--text-faint);
}

.search-scope-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--accent);
  flex-shrink: 0;
  display: none; /* shown when context is set */
}
.search-scope-dot.visible { display: block; }

.search-results-list {
  overflow-y: auto;
  flex: 1;
  padding: 8px 0 8px;
}

/* Empty / hint states */
.search-hint-state,
.search-empty-state,
.search-loading-state {
  padding: 28px 20px;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-faint);
}
.search-loading-state { color: var(--text-muted); }

/* Result items */
.search-result-item {
  padding: 10px 18px;
  cursor: pointer;
  border-bottom: 1px solid var(--border);
  transition: background 0.1s;
}
.search-result-item:last-child { border-bottom: none; }
.search-result-item:hover,
.search-result-item.is-active {
  background: var(--bg-card-hover);
}

.search-result-meta {
  display: flex;
  align-items: baseline;
  gap: 8px;
  margin-bottom: 4px;
}

.search-result-title {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.search-result-sub {
  font-size: 0.75rem;
  color: var(--text-faint);
  flex-shrink: 0;
  background: var(--bg);
  border: 1px solid var(--border);
  padding: 1px 6px;
  border-radius: 10px;
  white-space: nowrap;
}

.search-result-snippet {
  font-size: 0.81rem;
  color: var(--text-muted);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  border-radius: 4px;
  padding: 3px 5px;
  margin: 0 -5px;
  transition: background 0.1s, color 0.1s;
}
.search-result-item:hover .search-result-snippet,
.search-result-item.is-active .search-result-snippet {
  background: var(--bg);
  color: var(--text);
}

.search-result-snippet mark {
  background: transparent;
  color: var(--accent-light);
  font-weight: 700;
}
[data-theme="light"] .search-result-snippet mark {
  color: var(--accent-deep);
}

.search-result-snippet-hint {
  font-size: 0.73rem;
  color: var(--text-faint);
  margin-top: 2px;
  font-style: italic;
}

/* Result count badge */
.search-results-header {
  padding: 6px 18px 2px;
  font-size: 0.73rem;
  color: var(--text-faint);
  font-weight: 500;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* ----------------------------------------------------------
   14c. PARAGRAPH POPUP
   ---------------------------------------------------------- */

.para-overlay {
  position: fixed;
  inset: 0;
  z-index: 400;
  background: rgba(0, 0, 0, 0.72);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px 16px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.18s ease;
}
.para-overlay.is-open {
  opacity: 1;
  pointer-events: auto;
}

.para-popup {
  position: relative;
  width: min(560px, 100%);
  max-height: calc(100vh - 80px);
  overflow-y: auto;
  background: var(--bg-card);
  border: 1px solid var(--border-strong);
  border-radius: 16px;
  box-shadow: var(--shadow-lg);
  padding: 28px 32px;
  transform: scale(0.95);
  transition: transform 0.18s ease;
}
.para-overlay.is-open .para-popup {
  transform: scale(1);
}

.para-popup-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 18px;
  gap: 12px;
}

.para-popup-src-link {
  color: inherit;
  text-decoration: none;
}
.para-popup-src-link:hover {
  color: var(--accent-light);
  text-decoration: underline;
}
.para-popup-src {
  font-size: 0.78rem;
  color: var(--text-faint);
  background: var(--bg);
  border: 1px solid var(--border);
  padding: 3px 10px;
  border-radius: 10px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  min-width: 0;
}

.para-popup-close {
  width: 30px;
  height: 30px;
  border-radius: 6px;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: background 0.12s, border-color 0.12s;
}
.para-popup-close:hover { background: var(--bg-card-hover); border-color: var(--border-strong); }

.para-popup-text {
  font-size: 0.95rem;
  line-height: 1.75;
  color: var(--text);
  white-space: pre-wrap;
  word-break: break-word;
}

.para-popup-text mark {
  background: rgba(99, 170, 201, 0.2);
  color: var(--accent-light);
  font-weight: 700;
  padding: 1px 2px;
  border-radius: 3px;
}
[data-theme="light"] .para-popup-text mark {
  background: rgba(23, 118, 164, 0.1);
  color: var(--accent-deep);
}

/* ----------------------------------------------------------
   14d. SEARCH RESPONSIVE
   ---------------------------------------------------------- */

@media (max-width: 700px) {
  .search-pill-hint,
  .search-pill-kbd { display: none; }
  .search-pill {
    width: 36px;
    height: 36px;
    padding: 0;
    justify-content: center;
    gap: 0;
  }
  .search-pill svg { opacity: 0.8; }
}

@media (max-width: 480px) {
  .search-overlay { padding-top: 60px; }
  .search-modal { border-radius: 12px; }
  .para-popup { padding: 20px 18px; border-radius: 12px; }
  .para-popup-close { width: 44px; height: 44px; border-radius: 8px; margin: -7px -7px -7px 0; }
}

/* ── Module rows (course home) ────────────────────────────────── */
.module-row {
  position: relative;
  padding-left: 8px;
  cursor: pointer;
  overflow: hidden;
}
.module-row-stripe {
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 4px;
  border-radius: 4px 0 0 4px;
}
.module-row--locked {
  opacity: 0.45;
  cursor: default;
  pointer-events: none;
}
.module-row-meta {
  font-size: 0.72rem;
  color: var(--text-muted);
  margin-top: 3px;
}
.module-row-right {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 6px;
  flex-shrink: 0;
  margin-left: 12px;
}
.module-row-progress {
  font-size: 0.72rem;
  color: var(--text-muted);
  white-space: nowrap;
}
.module-row-done {
  font-size: 0.85rem;
  color: var(--accent-light);
  font-weight: 600;
}
.module-lock-icon {
  color: var(--text-muted);
  opacity: 0.6;
}


/* ── Syllabus / Outline page ──────────────────────────────────── */
.outline-page {
  max-width: 860px;
  margin: 0 auto;
  padding: 48px 32px;
}

.outline-header {
  margin-bottom: 40px;
}
.outline-header-title {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 6px;
}
.outline-header-title h1 {
  font-size: 1.5rem;
  font-weight: 700;
  margin: 0;
}
.outline-header-sub {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin: 0 0 16px;
}
.outline-controls {
  display: flex;
  gap: 8px;
}

/* Expand/Collapse and Syllabus button */
.btn-outline-ctrl {
  padding: 4px 12px;
  font-size: 0.75rem;
  font-family: inherit;
  font-weight: 500;
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  background: var(--bg-surface);
  color: var(--text-muted);
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
  user-select: none;
  white-space: nowrap;
}
.btn-outline-ctrl:hover {
  background: var(--bg-card);
  color: var(--text);
  border-color: var(--accent);
}

/* Hold-to-unlock fill animation */
.btn-outline-ctrl.holding {
  animation: holdFill 2s linear forwards;
  color: var(--text);
}
@keyframes holdFill {
  from { background: var(--bg-surface); }
  to   { background: var(--accent); border-color: var(--accent); color: #fff; }
}

/* Module accordions */
.outline-modules {
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.outline-module {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
}
.outline-summary {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 20px;
  cursor: pointer;
  list-style: none;
  user-select: none;
  transition: background 0.15s;
}
.outline-summary::-webkit-details-marker { display: none; }
.outline-summary:hover { background: var(--bg-card); }

.outline-accent-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex-shrink: 0;
}
.outline-module-num {
  font-size: 0.72rem;
  font-weight: 700;
  font-family: 'SF Mono', 'Fira Code', monospace;
  color: var(--text-faint);
  flex-shrink: 0;
  width: 2rem;
}
.outline-summary-title {
  font-weight: 600;
  font-size: 0.9375rem;
  flex: 1;
  min-width: 0;
}
.outline-summary-meta {
  font-size: 0.72rem;
  color: var(--text-faint);
  flex-shrink: 0;
  white-space: nowrap;
}
.outline-chevron {
  flex-shrink: 0;
  color: var(--text-faint);
  transition: transform 0.2s ease;
  display: flex;
  align-items: center;
}
.outline-module[open] .outline-chevron { transform: rotate(180deg); }

.outline-body {
  border-top: 1px solid var(--border);
  padding: 16px 20px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.outline-group { display: flex; flex-direction: column; gap: 6px; }
.outline-group-label {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--text-faint);
}
.outline-items {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.outline-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 5px 10px;
  border-radius: 5px;
  transition: background 0.12s;
}
.outline-item:hover { background: var(--bg-card); }
.outline-item-icon { flex-shrink: 0; display: flex; align-items: center; }
.outline-icon-reading { color: var(--accent); }
.outline-icon-quiz    { color: var(--warn); }
.outline-icon-lab     { color: var(--success); }

.outline-item-link {
  flex: 1;
  font-size: 0.875rem;
  color: var(--text);
  text-decoration: none;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.outline-item-link:hover { color: var(--accent-light); text-decoration: underline; }
.outline-item-meta {
  flex-shrink: 0;
  font-size: 0.72rem;
  color: var(--text-faint);
}

/* Locked module state */
.outline-module-locked { opacity: 0.6; }
.outline-module-locked .outline-summary-title { color: var(--text-muted); }

.outline-lock-badge {
  display: inline-flex;
  align-items: center;
  gap: 3px;
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-faint);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  flex-shrink: 0;
}
.outline-locked-note {
  font-size: 0.78rem;
  color: var(--text-faint);
  margin-bottom: 12px;
  padding: 6px 10px;
  background: var(--bg-card);
  border-radius: 5px;
  border-left: 2px solid var(--border-strong);
}
.outline-item-disabled {
  color: var(--text-faint);
  cursor: default;
  pointer-events: none;
}
.outline-item.outline-item-locked:hover { background: transparent; }

/* H3-level sub-topic indentation */
.outline-topic-h3 { padding-left: 28px; }
.outline-topic-h3 .outline-item-icon { opacity: 0.6; }
.outline-topic-h3 .outline-item-link  { font-size: 0.82rem; color: var(--text-muted); }
.outline-topic-h3 .outline-item-link:hover { color: var(--accent-light); }

/* Flat quiz / checkpoint rows (not inside <details>) */
.outline-item-flat {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: 6px;
  margin: 2px 0;
  transition: background 0.15s;
}
.outline-item-flat:not(.outline-item-locked):hover { background: var(--bg-card); }
.outline-item-flat .outline-item-meta { margin-left: auto; }

/* Completion check mark */
.outline-done-check {
  font-size: 0.78rem;
  color: var(--success);
  font-weight: 700;
  flex-shrink: 0;
}

/* Colab launch link inside lab section */
.outline-lab-open {
  padding: 4px 0 10px;
}

/* Lab objective text (non-link) */
.outline-item-obj {
  color: var(--text-muted);
  font-size: 0.82rem;
  cursor: default;
  pointer-events: none;
}

/* Admin badge */
.admin-badge {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  background: rgba(124, 58, 237, 0.13);
  color: #a78bfa;
  border: 1px solid rgba(124, 58, 237, 0.4);
  border-radius: 20px;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  font-family: 'SF Mono', 'Fira Code', monospace;
}

@media (max-width: 600px) {
  .outline-page { padding: 28px 16px; }
  .outline-summary { padding: 12px 16px; }
  .outline-summary-meta { display: none; }
  .outline-body { padding: 12px 16px; }
}

/* ── Mobile Responsive Overrides ─────────────────────────────── */

/* ── 640px: nav compression + course overview ──────────────────*/
@media (max-width: 640px) {
  /* Shrink nav padding and hide breadcrumb intermediate crumbs */
  .nav-inner { padding: 0 12px; gap: 8px; }
  .nav-breadcrumb {
    font-size: 0.78rem;
    min-width: 0;
  }
  /* Hide all breadcrumb links except the last (current page) */
  .nav-breadcrumb a,
  .nav-breadcrumb .bc-sep { display: none; }

  /* Course / prereq / supplement overview */
  .course-overview { padding: 24px 16px 60px; }
  .course-ov-title { font-size: 1.3rem !important; }
  .course-ov-desc  { font-size: 0.875rem; }

  /* Module rows */
  .reading-row-desc { display: none; }

  /* Reading nav buttons — stack vertically */
  .reading-nav-row {
    flex-direction: column;
    gap: 8px;
  }
  .reading-nav-btn { width: 100%; justify-content: center; }

  /* Equation breakdown */
  .eq-breakdown { padding: 14px 14px; }
  .eq-term { gap: 10px; }

  /* Quiz option labels — more tap-friendly */
  .option-label { padding: 12px 14px; align-items: center; }
  .option-label input[type="radio"] { width: 18px; height: 18px; margin-top: 0; }

  /* Quiz score card */
  .quiz-score-card { padding: 20px 16px 18px; }
  .quiz-score-pct  { font-size: 2.2rem; }

  /* Quiz submit button — full width */
  .quiz-submit-btn { width: 100%; }

  /* Drill card — mobile */
  .drill-card-front,
  .drill-card-back    { padding: 24px 20px; font-size: 0.98rem; }
  .drill-card-front .katex { font-size: 1.3em; }
  .drill-card         { cursor: pointer; }  /* whole card tappable */

  .btn-drill-primary  { width: 100%; }
  .drill-rating       { width: 100%; }
  .btn-drill-again,
  .btn-drill-got      { flex: 1; min-width: 0; }

  /* Summary actions — stack on very small screens */
  .drill-summary-actions,
  .drill-complete-actions { flex-direction: column; width: 100%; }
  .drill-summary-actions .btn-drill-primary,
  .drill-summary-actions .btn-drill-secondary,
  .drill-complete-actions .btn-drill-primary,
  .drill-complete-actions .btn-drill-secondary { width: 100%; }

  /* Lab colab card — stack vertically */
  .lab-colab-card {
    flex-direction: column;
    align-items: flex-start;
    padding: 18px 18px;
    gap: 16px;
  }
  .lab-colab-btn { width: 100%; justify-content: center; }

  /* Outline / syllabus */
  .outline-header-title h1 { font-size: 1.25rem; }
  .outline-module-num { display: none; }
}

/* ── 480px: tighter reading content typography ──────────────────*/
@media (max-width: 480px) {
  /* Reading content headings */
  .reading-content h2 { font-size: 1.1rem; }
  .reading-content h3 { font-size: 0.975rem; }

  /* Tables: horizontal scroll wrapper (applied via JS is not available
     here, so we allow the table to scroll within the content column) */
  .reading-content table {
    display: block;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    font-size: 0.78rem;
  }

  /* Code blocks — reduce padding */
  .reading-content pre { padding: 12px 12px; }

  /* Course card body padding */
  .course-card-body { padding: 16px 16px 18px; }

  /* Meta pills — allow wrap */
  .course-ov-meta { flex-wrap: wrap; gap: 6px; }

  /* Densification canvas — cap width so it doesn't overflow */
  .densification-canvas { max-width: 100%; height: auto; }

  /* Catalog hero tagline */
  .catalog-hero-inner p { font-size: 0.9rem; }
}

/* ── Animation embeds ────────────────────────────────────── */
.gauss-elim-embed,
.solution-set-embed,
.parametric-embed,
.subspace-embed,
.span-gauss-embed,
.li-test-embed,
.rank-nullity-embed,
.sh-viz-embed {
  margin: 1rem 0 2rem;
}

/* ── Gauss elimination animation ─────────────────────────── */
.gauss-anim-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 20px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
}
.gauss-canvas {
  max-width: 100%;
  height: auto;
  display: block;
}
.gauss-controls {
  display: flex;
  align-items: center;
  gap: 10px;
}
.gauss-btn {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 8px;
  padding: 5px 14px;
  font-size: 0.85rem;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  min-width: 36px;
}
.gauss-btn:hover:not(:disabled) {
  background: var(--bg-card);
  border-color: var(--accent);
  color: var(--accent-light);
}
.gauss-btn:disabled {
  opacity: 0.3;
  cursor: default;
}
.gauss-play-btn {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  padding: 5px 18px;
}
.gauss-play-btn:hover:not(:disabled) {
  background: var(--accent-light);
  border-color: var(--accent-light);
  color: #fff;
}
.gauss-step-counter {
  font-size: 0.8rem;
  color: var(--text-faint);
  min-width: 52px;
  text-align: center;
}

/* ── Pyodide code runner ───────────────────────────────────── */
.code-runner-wrap {
  display: flex;
  flex-direction: column;
  gap: 0;
  margin-bottom: 2rem;
}
.code-runner-wrap pre {
  margin-bottom: 0;
  border-bottom-left-radius: 0;
  border-bottom-right-radius: 0;
}
.code-run-btn {
  align-self: flex-start;
  margin-top: 0;
  padding: 5px 16px;
  font-size: 0.78rem;
  font-family: system-ui, sans-serif;
  font-weight: 600;
  background: var(--accent);
  color: #fff;
  border: none;
  border-top-left-radius: 0;
  border-top-right-radius: 0;
  border-bottom-left-radius: 6px;
  border-bottom-right-radius: 6px;
  cursor: pointer;
  transition: background 0.15s;
}
.code-run-btn:hover:not(:disabled) { background: var(--accent-light); }
.code-run-btn:disabled { opacity: 0.55; cursor: default; }
.code-output {
  margin-top: 6px;
  padding: 10px 14px;
  font-family: 'Courier New', monospace;
  font-size: 0.82rem;
  line-height: 1.55;
  white-space: pre-wrap;
  border-radius: 6px;
  border-left: 3px solid;
}
.code-output--pending {
  border-color: var(--border);
  color: var(--text-faint);
  background: var(--bg-surface);
}
.code-output--ok {
  border-color: #52ab97;
  color: var(--text);
  background: var(--bg-surface);
}
.code-output--err {
  border-color: #f87171;
  color: #f87171;
  background: color-mix(in srgb, #f87171 6%, transparent);
}

/* ── Notation FAB ─────────────────────────────────────────── */
.notation-fab {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  font-weight: 700;
  font-family: serif;
  box-shadow: 0 4px 16px rgba(0,0,0,0.35);
  z-index: 800;
  transition: background 0.15s, transform 0.15s, box-shadow 0.15s;
}
.notation-fab:hover {
  background: var(--accent-light);
  transform: scale(1.08);
  box-shadow: 0 6px 20px rgba(0,0,0,0.4);
}
[data-theme="light"] .notation-fab {
  color: #fff;
}

/* ── Notation modal overlay ───────────────────────────────── */
.notation-overlay {
  display: flex;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.55);
  z-index: 900;
  align-items: center;
  justify-content: center;
  padding: 24px 16px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.22s ease;
}
.notation-overlay.is-open {
  opacity: 1;
  pointer-events: auto;
}
.notation-modal {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  width: 100%;
  max-width: 680px;
  max-height: 80vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: 0 20px 60px rgba(0,0,0,0.5);
  transition: transform 0.28s cubic-bezier(0.32, 0.72, 0, 1);
  position: relative;
}
.notation-modal-head {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 48px 16px 20px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.notation-modal-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
  flex-shrink: 0;
}
.notation-search {
  flex: 1;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 7px 12px;
  font-size: 0.875rem;
  color: var(--text);
  outline: none;
}
.notation-search:focus {
  border-color: var(--accent);
}
.notation-close-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-faint);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
  z-index: 1;
}
.notation-close-btn:hover {
  color: var(--text);
  background: var(--bg-card);
}

/* ── Notation list ────────────────────────────────────────── */
.notation-list {
  overflow-y: auto;
  padding: 8px 0;
  flex: 1;
}
.notation-entry {
  display: grid;
  grid-template-columns: 7rem 1fr;
  gap: 6px 20px;
  align-items: start;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
}
.notation-entry:last-child { border-bottom: none; }
.notation-sym {
  font-size: 1.15rem;
  color: var(--text);
  padding-top: 2px;
  min-width: 0;
  overflow-x: clip;
}
.notation-name {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 3px;
}
.notation-desc {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.5;
}
.notation-sources {
  margin-top: 6px;
  font-size: 0.75rem;
  color: var(--text-faint);
}
.notation-source-link {
  color: var(--accent-light);
  text-decoration: none;
}
.notation-source-link:hover { text-decoration: underline; }
.notation-empty {
  padding: 32px 20px;
  text-align: center;
  font-size: 0.875rem;
  color: var(--text-faint);
}

@media (max-width: 640px) {
  /* FAB: safe-area-aware bottom offset */
  .notation-fab {
    bottom: calc(20px + env(safe-area-inset-bottom, 0px));
    right: 16px;
    width: 44px;
    height: 44px;
    font-size: 1.1rem;
  }

  /* Bottom sheet overlay */
  .notation-overlay {
    align-items: flex-end;
    justify-content: stretch;
    padding: 0;
  }

  /* Slide up from below; full width, rounded top corners only */
  .notation-modal {
    max-height: 85vh;
    max-width: 100%;
    border-radius: 20px 20px 0 0;
    border-bottom: none;
    transform: translateY(100%);
    padding-bottom: env(safe-area-inset-bottom, 0px);
  }
  .notation-overlay.is-open .notation-modal {
    transform: translateY(0);
  }

  /* Larger close button touch target on mobile */
  .notation-close-btn {
    width: 44px;
    height: 44px;
    top: 8px;
    right: 8px;
  }

  .notation-modal-head {
    padding-right: 52px;
  }

  /* Stack symbol above body text — avoids wide KaTeX overflowing into adjacent column */
  .notation-entry {
    grid-template-columns: 1fr;
    gap: 6px 0;
    padding: 12px 16px;
  }
  .notation-sym { padding-top: 0; overflow: visible; }
}

/* ================================================================
   SYNTAX HIGHLIGHTING  —  custom hljs theme using platform palette
   Dark: navy/steel-blue  ·  Light: pastel/mauve
   ================================================================ */

/* ── hljs: font, layout, and theme-aware colors (hardcoded per theme) ── */

.hljs {
  display: block;
  overflow-x: auto;
  padding: 0;
  font-family: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', 'Courier New', monospace;
  font-size: 0.83em;
  line-height: 1.6;
  background: transparent;
}

/* ── Dark theme ── */
[data-theme="dark"] .hljs                         { color: #c9d1d9; }
[data-theme="dark"] .hljs-keyword,
[data-theme="dark"] .hljs-literal                 { color: #b1aad1; }
[data-theme="dark"] .hljs-built_in                { color: #63aac9; }
[data-theme="dark"] .hljs-string                  { color: #52ab97; }
[data-theme="dark"] .hljs-subst                   { color: #c9d1d9; }
[data-theme="dark"] .hljs-number                  { color: #fbbf24; }
[data-theme="dark"] .hljs-comment,
[data-theme="dark"] .hljs-doctag                  { color: #4d6f87; font-style: italic; }
[data-theme="dark"] .hljs-title.function_,
[data-theme="dark"] .hljs-title.function_.invoke__ { color: #63aac9; }
[data-theme="dark"] .hljs-title.class_,
[data-theme="dark"] .hljs-title.class_.inherited__ { color: #8ab4cc; }
[data-theme="dark"] .hljs-meta,
[data-theme="dark"] .hljs-meta .hljs-keyword      { color: #fbbf24; }
[data-theme="dark"] .hljs-attr,
[data-theme="dark"] .hljs-variable                { color: #8ab4cc; }
[data-theme="dark"] .hljs-operator,
[data-theme="dark"] .hljs-params                  { color: #c9d1d9; }
[data-theme="dark"] .hljs-punctuation             { color: #8ab4cc; }
[data-theme="dark"] .hljs-type                    { color: #8ab4cc; }

/* ── Light theme ── */
[data-theme="light"] .hljs                         { color: #1e1a2a; }
[data-theme="light"] .hljs-keyword,
[data-theme="light"] .hljs-literal                 { color: #7c3aed; }
[data-theme="light"] .hljs-built_in                { color: #1776a4; }
[data-theme="light"] .hljs-string                  { color: #0d7490; }
[data-theme="light"] .hljs-subst                   { color: #1e1a2a; }
[data-theme="light"] .hljs-number                  { color: #b45309; }
[data-theme="light"] .hljs-comment,
[data-theme="light"] .hljs-doctag                  { color: #9b92af; font-style: italic; }
[data-theme="light"] .hljs-title.function_,
[data-theme="light"] .hljs-title.function_.invoke__ { color: #1776a4; }
[data-theme="light"] .hljs-title.class_,
[data-theme="light"] .hljs-title.class_.inherited__ { color: #2a5757; }
[data-theme="light"] .hljs-meta,
[data-theme="light"] .hljs-meta .hljs-keyword      { color: #b45309; }
[data-theme="light"] .hljs-attr,
[data-theme="light"] .hljs-variable                { color: #1776a4; }
[data-theme="light"] .hljs-operator,
[data-theme="light"] .hljs-params                  { color: #1e1a2a; }
[data-theme="light"] .hljs-punctuation             { color: #1776a4; }
[data-theme="light"] .hljs-type                    { color: #2a5757; }

/* ----------------------------------------------------------
   DRILL — course overview rows
   ---------------------------------------------------------- */
.drill-row {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 18px;
  border-radius: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  margin: 4px 0;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}
.drill-row:hover { background: var(--bg-card-hover); border-color: var(--border-strong); }
.drill-row-icon { color: var(--accent-light); flex-shrink: 0; display: flex; align-items: center; }
.drill-row-info { flex: 1; min-width: 0; }
.drill-row-title { font-weight: 600; font-size: 0.95rem; color: var(--text); }
.drill-row-meta  { font-size: 0.8rem; color: var(--text-muted); margin-top: 2px; }
.drill-row-bar   { height: 4px; background: var(--bg-surface); border-radius: 2px; margin-top: 6px; overflow: hidden; }
.drill-row-fill  { height: 100%; background: var(--accent-light); border-radius: 2px; transition: width 0.3s; }
.drill-row-done  { font-size: 0.8rem; color: var(--success, #4ade80); font-weight: 700; flex-shrink: 0; }

/* ----------------------------------------------------------
   DRILL — card flip page
   ---------------------------------------------------------- */
.drill-page {
  max-width: 680px;
  margin: 0 auto;
  padding: 24px 16px 48px;
}
.drill-header { margin-bottom: 24px; }
.drill-title  { font-size: 1.4rem; font-weight: 700; color: var(--text); margin: 8px 0 4px; }
.drill-subtitle { font-size: 0.88rem; color: var(--text-muted); margin: 0; }

.drill-progress-bar {
  height: 6px;
  background: var(--bg-surface);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 6px;
}
.drill-progress-fill {
  height: 100%;
  background: var(--accent-light);
  border-radius: 3px;
  transition: width 0.3s;
}
.drill-progress-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  text-align: right;
  margin-bottom: 2px;
}
.drill-box-label {
  font-size: 0.74rem;
  color: var(--text-faint);
  text-align: center;
  margin-bottom: 14px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* 3-D card flip — grid trick: both faces in same cell so card height = max(front, back) */
.drill-card-scene {
  perspective: 900px;
  margin: 0 auto 24px;
}
.drill-card {
  display: grid;
  width: 100%;
  transform-style: preserve-3d;
  transition: transform 0.45s cubic-bezier(0.4, 0.2, 0.2, 1);
  cursor: default;
}
.drill-card.is-flipped {
  transform: rotateY(180deg);
}
.drill-card-front,
.drill-card-back {
  grid-area: 1 / 1;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: 12px;
  border: 1px solid var(--border-strong);
  background: var(--bg-card);
  padding: 32px;
  font-size: 1.05rem;
  line-height: 1.65;
  color: var(--text);
  min-height: 160px;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  box-sizing: border-box;
}
.drill-card-back {
  transform: rotateY(180deg);
  background: var(--bg-card);
  text-align: left;
  align-items: flex-start;
  justify-content: flex-start;
  font-size: 0.9rem;
  flex-direction: column;
  gap: 0;
}
/* tighten markdown inside back face */
.drill-card-back p    { margin: 0 0 0.5em; }
.drill-card-back p:last-child { margin-bottom: 0; }
.drill-card-back ul, .drill-card-back ol { margin: 0.4em 0 0.4em 1.2em; padding: 0; }
.drill-card-back li   { margin: 0.2em 0; }
.drill-card-back strong { color: var(--accent-light); }
.drill-card-back em   { color: var(--text-muted); }
/* KaTeX — keep inline math visible; display math in readings scrolls horizontally */
.katex-display > .katex,
.katex { overflow: visible; }

/* KaTeX inside cards — size adjustments */
.drill-card-front .katex-display { margin: 0.4em 0; }
.drill-card-front .katex          { font-size: 1.6em; }
.drill-card-back  .katex          { font-size: 1em; }

.drill-controls {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
}
.drill-rating {
  display: flex;
  gap: 12px;
  justify-content: center;
}
.btn-drill-primary {
  padding: 10px 32px;
  background: var(--accent);
  color: var(--text-on-accent);
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
}
.btn-drill-primary:hover { background: var(--accent-hover); }
.btn-drill-secondary {
  padding: 10px 24px;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border-strong);
  border-radius: 8px;
  font-size: 0.9rem;
  cursor: pointer;
  transition: background 0.15s;
}
.btn-drill-secondary:hover { background: var(--bg-card-hover); }
.btn-drill-again {
  padding: 10px 28px;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border-strong);
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
  min-width: 110px;
}
.btn-drill-again:hover { background: rgba(255,80,80,0.12); border-color: rgba(255,80,80,0.4); color: #f87171; }
.btn-drill-got {
  padding: 10px 28px;
  background: var(--accent);
  color: var(--text-on-accent);
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
  min-width: 110px;
}
.btn-drill-got:hover { background: var(--accent-hover); }
.drill-hint {
  text-align: center;
  font-size: 0.75rem;
  color: var(--text-faint);
  margin: 0;
}
.drill-hint-touch { display: none; }
@media (pointer: coarse) {
  .drill-hint-kb    { display: none; }
  .drill-hint-touch { display: block; }
}

/* Summary and complete screens */
.drill-summary, .drill-complete {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
  padding: 40px 16px;
  text-align: center;
}
.drill-summary h2, .drill-complete h2 { font-size: 1.4rem; margin: 0; }
.drill-complete-icon { font-size: 3rem; line-height: 1; }
.drill-summary-stats {
  display: flex;
  gap: 32px;
}
.drill-stat { display: flex; flex-direction: column; align-items: center; gap: 4px; }
.drill-stat-num   { font-size: 2rem; font-weight: 700; color: var(--accent-light); }
.drill-stat-label { font-size: 0.8rem; color: var(--text-muted); }
.drill-summary-actions, .drill-complete-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ----------------------------------------------------------
   SYLLABUS — Practice Decks section
   ---------------------------------------------------------- */
.outline-practice-section {
  margin-top: 24px;
  border-top: 1px solid var(--border);
  padding-top: 20px;
}
.outline-practice-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-faint);
  margin-bottom: 10px;
  padding: 0 4px;
}
.outline-drill-row {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  border-radius: 7px;
  margin: 3px 0;
  cursor: pointer;
  transition: background 0.15s;
  flex-wrap: wrap;
}
.outline-drill-row:hover { background: var(--bg-card-hover); }
.outline-icon-drill { color: var(--accent-light); flex-shrink: 0; }
.outline-drill-title { font-size: 0.88rem; font-weight: 600; color: var(--text); flex: 1; min-width: 120px; }
.outline-drill-meta  { font-size: 0.76rem; color: var(--text-muted); margin-left: auto; white-space: nowrap; }
.outline-drill-bar   { width: 100%; height: 3px; background: var(--bg-surface); border-radius: 2px; margin-top: 4px; overflow: hidden; flex-basis: 100%; }
.outline-drill-fill  { height: 100%; background: var(--accent-light); border-radius: 2px; transition: width 0.3s; }