/* MIT 5.95J Learning App — Design System */

/* ========== CSS Variables ========== */
:root {
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.15);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.2);
  --transition: 0.2s ease;
  --max-width: 1200px;
}

/* Dark Theme (default) */
[data-theme="dark"] {
  --bg-primary: #0f1117;
  --bg-secondary: #1a1d27;
  --bg-card: #1e2130;
  --bg-hover: #262a3a;
  --bg-input: #252836;
  --border: #2d3148;
  --border-hover: #3d4260;
  --text-primary: #e8eaf0;
  --text-secondary: #9ca3b8;
  --text-muted: #6b7394;
  --accent: #6c63ff;
  --accent-hover: #7b73ff;
  --accent-subtle: rgba(108,99,255,0.12);
  --success: #34d399;
  --success-subtle: rgba(52,211,153,0.12);
  --warning: #fbbf24;
  --warning-subtle: rgba(251,191,36,0.12);
  --danger: #f87171;
  --danger-subtle: rgba(248,113,113,0.12);
  --info: #60a5fa;
  --info-subtle: rgba(96,165,250,0.12);
}

/* Light Theme */
[data-theme="light"] {
  --bg-primary: #f8f9fc;
  --bg-secondary: #ffffff;
  --bg-card: #ffffff;
  --bg-hover: #f0f1f5;
  --bg-input: #f0f1f5;
  --border: #e2e4ea;
  --border-hover: #c8ccd8;
  --text-primary: #1a1d27;
  --text-secondary: #5a6178;
  --text-muted: #8b92a8;
  --accent: #5b52e0;
  --accent-hover: #4a42cc;
  --accent-subtle: rgba(91,82,224,0.08);
  --success: #10b981;
  --success-subtle: rgba(16,185,129,0.08);
  --warning: #f59e0b;
  --warning-subtle: rgba(245,158,11,0.08);
  --danger: #ef4444;
  --danger-subtle: rgba(239,68,68,0.08);
  --info: #3b82f6;
  --info-subtle: rgba(59,130,246,0.08);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}

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

/* ========== Layout ========== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.page-wrapper {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ========== Navigation ========== */
.nav {
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  padding: 16px 0;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
}

.nav .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-primary);
}

.nav-brand-icon {
  width: 36px;
  height: 36px;
  background: var(--accent);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
}

.nav-links {
  display: flex;
  gap: 8px;
  align-items: center;
  list-style: none;
  flex-wrap: wrap;
}

.nav-links a {
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition);
}

.nav-links a:hover, .nav-links a.active {
  background: var(--accent-subtle);
  color: var(--accent);
}

.nav-actions {
  display: flex;
  gap: 8px;
  align-items: center;
}

/* ========== Theme Toggle ========== */
.theme-toggle {
  width: 40px;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  transition: all var(--transition);
}

.theme-toggle:hover {
  border-color: var(--border-hover);
  color: var(--text-primary);
}

/* ========== Headings ========== */
.page-header {
  padding: 48px 0 32px;
}

.page-header h1 {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
}

.page-header p {
  color: var(--text-secondary);
  font-size: 1.1rem;
}

h2 { font-size: 1.5rem; font-weight: 700; letter-spacing: -0.01em; }
h3 { font-size: 1.2rem; font-weight: 600; }

/* ========== Cards ========== */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 24px;
  transition: all var(--transition);
}

.card:hover {
  border-color: var(--border-hover);
  box-shadow: var(--shadow-sm);
}

.card-clickable {
  cursor: pointer;
}

.card-clickable:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

/* ========== Session Cards Grid ========== */
.sessions-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
  margin-bottom: 48px;
}

.session-card {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.session-card-header {
  display: flex;
  align-items: flex-start;
  gap: 14px;
}

.session-number {
  width: 44px;
  height: 44px;
  min-width: 44px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.1rem;
}

.session-number.not-started { background: var(--bg-hover); color: var(--text-muted); }
.session-number.in-progress { background: var(--warning-subtle); color: var(--warning); }
.session-number.completed { background: var(--success-subtle); color: var(--success); }

.session-card-title {
  font-weight: 600;
  font-size: 1rem;
  line-height: 1.4;
}

.session-card-subtitle {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

.session-card-footer {
  display: flex;
  gap: 8px;
  margin-top: auto;
}

/* ========== Badges ========== */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 600;
  white-space: nowrap;
}

.badge-default { background: var(--bg-hover); color: var(--text-muted); }
.badge-accent { background: var(--accent-subtle); color: var(--accent); }
.badge-success { background: var(--success-subtle); color: var(--success); }
.badge-warning { background: var(--warning-subtle); color: var(--warning); }
.badge-danger { background: var(--danger-subtle); color: var(--danger); }
.badge-info { background: var(--info-subtle); color: var(--info); }

/* ========== Buttons ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  font-family: inherit;
  white-space: nowrap;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover { background: var(--accent-hover); transform: translateY(-1px); }

.btn-secondary {
  background: var(--bg-hover);
  color: var(--text-primary);
  border: 1px solid var(--border);
}
.btn-secondary:hover { border-color: var(--border-hover); }

.btn-success { background: var(--success); color: #fff; }
.btn-success:hover { filter: brightness(1.1); }

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

.btn-sm { padding: 6px 12px; font-size: 0.8rem; }
.btn-lg { padding: 14px 28px; font-size: 1rem; }

.btn-icon {
  width: 40px;
  height: 40px;
  padding: 0;
  border-radius: var(--radius-sm);
}

/* ========== Progress Ring ========== */
.progress-ring-wrap {
  display: flex;
  align-items: center;
  justify-content: center;
}

.progress-ring {
  transform: rotate(-90deg);
}

.progress-ring-bg {
  fill: none;
  stroke: var(--border);
}

.progress-ring-fill {
  fill: none;
  stroke: var(--accent);
  stroke-linecap: round;
  transition: stroke-dashoffset 0.8s ease;
}

.progress-ring-text {
  font-size: 2rem;
  font-weight: 800;
  fill: var(--text-primary);
}

.progress-ring-label {
  font-size: 0.85rem;
  fill: var(--text-secondary);
}

/* ========== Stats Row ========== */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 16px;
  margin-bottom: 32px;
}

.stat-card {
  text-align: center;
  padding: 20px;
}

.stat-value {
  font-size: 2rem;
  font-weight: 800;
  color: var(--accent);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* ========== Accordion ========== */
.accordion { display: flex; flex-direction: column; gap: 8px; }

.accordion-item {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.accordion-trigger {
  width: 100%;
  padding: 16px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  background: var(--bg-card);
  border: none;
  color: var(--text-primary);
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background var(--transition);
  text-align: left;
}

.accordion-trigger:hover { background: var(--bg-hover); }

.accordion-trigger .arrow {
  transition: transform var(--transition);
  font-size: 0.8rem;
  color: var(--text-muted);
}

.accordion-item.open .accordion-trigger .arrow { transform: rotate(180deg); }

.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.accordion-item.open .accordion-content {
  max-height: 2000px;
}

.accordion-body {
  padding: 0 20px 20px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ========== Form Elements ========== */
.textarea, .input {
  width: 100%;
  padding: 12px 16px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.95rem;
  line-height: 1.6;
  transition: border-color var(--transition);
  resize: vertical;
}

.textarea:focus, .input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-subtle);
}

.textarea { min-height: 120px; }

.select {
  padding: 10px 14px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
}

/* ========== Quiz Styles ========== */
.quiz-option {
  display: block;
  width: 100%;
  padding: 16px 20px;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: inherit;
  cursor: pointer;
  transition: all var(--transition);
  text-align: left;
  margin-bottom: 10px;
}

.quiz-option:hover { border-color: var(--accent); background: var(--accent-subtle); }

.quiz-option.correct {
  border-color: var(--success);
  background: var(--success-subtle);
}

.quiz-option.incorrect {
  border-color: var(--danger);
  background: var(--danger-subtle);
}

.quiz-option.dimmed {
  opacity: 0.5;
  pointer-events: none;
}

.quiz-explanation {
  padding: 16px 20px;
  border-radius: var(--radius-md);
  margin-top: 16px;
  line-height: 1.6;
}

.quiz-explanation.correct-bg { background: var(--success-subtle); color: var(--success); }
.quiz-explanation.incorrect-bg { background: var(--danger-subtle); color: var(--danger); }

.quiz-progress {
  height: 6px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 32px;
}

.quiz-progress-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 999px;
  transition: width 0.3s ease;
}

/* ========== Flashcard Styles ========== */
.flashcard-container {
  perspective: 1200px;
  width: 100%;
  max-width: 600px;
  margin: 0 auto;
}

.flashcard {
  width: 100%;
  min-height: 300px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
}

.flashcard.flipped { transform: rotateY(180deg); }

.flashcard-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: var(--radius-lg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px;
  text-align: center;
}

.flashcard-front {
  background: var(--bg-card);
  border: 2px solid var(--border);
  color: var(--text-primary);
  font-size: 1.2rem;
  font-weight: 600;
  line-height: 1.6;
}

.flashcard-back {
  background: var(--accent-subtle);
  border: 2px solid var(--accent);
  transform: rotateY(180deg);
  color: var(--text-primary);
  font-size: 1.05rem;
  line-height: 1.7;
}

.flashcard-rating {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin-top: 24px;
  flex-wrap: wrap;
}

.rating-btn {
  padding: 10px 20px;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  color: var(--text-primary);
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: all var(--transition);
}

.rating-btn:hover { border-color: var(--accent); }
.rating-btn.again { border-color: var(--danger); color: var(--danger); }
.rating-btn.hard { border-color: var(--warning); color: var(--warning); }
.rating-btn.good { border-color: var(--success); color: var(--success); }
.rating-btn.easy { border-color: var(--info); color: var(--info); }

/* ========== Journal Styles ========== */
.journal-list { display: flex; flex-direction: column; gap: 16px; }

.journal-entry {
  position: relative;
}

.journal-entry-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
  flex-wrap: wrap;
  gap: 8px;
}

.journal-date {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.journal-entry-body {
  color: var(--text-secondary);
  line-height: 1.7;
  white-space: pre-wrap;
}

.journal-actions {
  display: flex;
  gap: 8px;
}

/* ========== Progress / Heatmap ========== */
.heatmap {
  display: grid;
  grid-template-columns: repeat(auto-fill, 18px);
  gap: 3px;
}

.heatmap-cell {
  width: 16px;
  height: 16px;
  border-radius: 3px;
  background: var(--bg-hover);
}

.heatmap-cell.active { background: var(--accent); }
.heatmap-cell.active-light { background: var(--accent-subtle); }

.progress-table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
}

.progress-table th, .progress-table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.progress-table th {
  font-weight: 600;
  color: var(--text-secondary);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ========== Quick Actions ========== */
.quick-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}

/* ========== Empty State ========== */
.empty-state {
  text-align: center;
  padding: 64px 24px;
  color: var(--text-muted);
}

.empty-state-icon {
  font-size: 3rem;
  margin-bottom: 16px;
}

.empty-state h3 {
  color: var(--text-secondary);
  margin-bottom: 8px;
}

/* ========== Section Divider ========== */
.section {
  margin-bottom: 40px;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
  gap: 16px;
  flex-wrap: wrap;
}

/* ========== Reading Card ========== */
.reading-card {
  padding: 20px;
  background: var(--bg-hover);
  border-radius: var(--radius-md);
  margin-bottom: 12px;
}

.reading-card h4 {
  font-weight: 600;
  margin-bottom: 4px;
}

.reading-card .author {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-bottom: 10px;
}

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

/* ========== Modal ========== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.6);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 24px;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition);
}

.modal-overlay.active {
  opacity: 1;
  pointer-events: all;
}

.modal {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  max-width: 560px;
  width: 100%;
  max-height: 80vh;
  overflow-y: auto;
  transform: translateY(20px);
  transition: transform var(--transition);
}

.modal-overlay.active .modal {
  transform: translateY(0);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.modal-close {
  width: 32px;
  height: 32px;
  border: none;
  background: var(--bg-hover);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
}

/* ========== Notification Toast ========== */
.toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  padding: 14px 24px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  font-weight: 500;
  z-index: 2000;
  transform: translateY(100px);
  opacity: 0;
  transition: all 0.3s ease;
}

.toast.show { transform: translateY(0); opacity: 1; }
.toast.success { border-left: 4px solid var(--success); }
.toast.error { border-left: 4px solid var(--danger); }

/* ========== Tab Bar (for filtering) ========== */
.tab-bar {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 24px;
  overflow-x: auto;
}

.tab {
  padding: 10px 18px;
  border: none;
  background: none;
  color: var(--text-muted);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  white-space: nowrap;
  transition: all var(--transition);
}

.tab:hover { color: var(--text-secondary); }
.tab.active { color: var(--accent); border-bottom-color: var(--accent); }

/* ========== Responsive ========== */
@media (max-width: 768px) {
  .container { padding: 0 16px; }
  .page-header h1 { font-size: 1.5rem; }
  .sessions-grid { grid-template-columns: 1fr; }
  .stats-row { grid-template-columns: repeat(2, 1fr); gap: 8px; }
  .stat-card { padding: 12px 8px; }
  .nav-links { display: none; }
  .nav-brand span { display: none; }
  .flashcard-face { padding: 20px 16px; font-size: 1rem; }
  .flashcard { min-height: 220px; }
  .flashcard-container { margin-bottom: 16px; }
  .flashcard-rating { gap: 8px; margin-top: 16px; }
  .rating-btn { padding: 12px 16px; flex: 1; min-width: 0; text-align: center; font-size: 0.85rem; }

  .mobile-nav {
    display: flex;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border);
    padding: 8px 4px;
    z-index: 100;
    justify-content: space-around;
  }

  .mobile-nav a {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    font-size: 0.7rem;
    color: var(--text-muted);
    padding: 4px 8px;
  }

  .mobile-nav a.active { color: var(--accent); }
  .mobile-nav a span.icon { font-size: 1.3rem; }

  .page-wrapper { padding-bottom: 72px; }
}

@media (min-width: 769px) {
  .mobile-nav { display: none; }
}

/* ========== Idea Action Buttons ========== */
.idea-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  align-items: center;
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
}
.idea-actions-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-right: 4px;
}
.idea-action-btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 7px 14px;
  border: 1.5px solid var(--border);
  border-radius: 100px;
  background: var(--bg-primary);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s ease;
}
.idea-action-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-subtle);
  transform: translateY(-1px);
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.15);
}
.idea-action-btn:active {
  transform: translateY(0);
}
.idea-action-btn:disabled {
  opacity: 0.6;
  cursor: wait;
}
.idea-action-btn[data-type="elaborate"]:hover { border-color: #8b5cf6; color: #8b5cf6; }
.idea-action-btn[data-type="case_study"]:hover { border-color: #06b6d4; color: #06b6d4; }
.idea-action-btn[data-type="analogy"]:hover { border-color: #f59e0b; color: #f59e0b; }
.idea-action-btn[data-type="eli5"]:hover { border-color: #22c55e; color: #22c55e; }
.idea-action-btn[data-type="listen"]:hover { border-color: var(--accent); color: var(--accent); }
.idea-action-btn.tts-active { border-color: var(--accent); background: var(--accent); color: #fff; }

/* TTS word highlighting */
.tts-word { transition: background 0.15s, color 0.15s; border-radius: 3px; padding: 0 1px; }
.tts-word.active {
  background: var(--accent);
  color: #fff;
  padding: 1px 3px;
  border-radius: 4px;
  box-shadow: 0 0 8px rgba(99, 102, 241, 0.4);
}

/* TTS Controls */
.tts-controls {
  display: flex;
  align-items: center;
  gap: 10px;
}
.tts-select {
  max-width: 180px;
  font-size: 0.78rem;
  padding: 5px 8px;
}
.tts-speed {
  display: flex;
  align-items: center;
  gap: 6px;
}
.tts-range {
  width: 70px;
  height: 4px;
  -webkit-appearance: none;
  appearance: none;
  background: var(--border);
  border-radius: 2px;
  outline: none;
}
.tts-range::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
}
@media (max-width: 768px) {
  .tts-controls { width: 100%; }
  .tts-select { flex: 1; }
}
.idea-action-icon { font-size: 0.9rem; }

/* Expand content card */
.expand-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  margin-top: 12px;
}
.expand-card-header {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 0.85rem;
}
.expand-card-header[data-type="elaborate"] { background: #8b5cf615; color: #8b5cf6; }
.expand-card-header[data-type="case_study"] { background: #06b6d415; color: #06b6d4; }
.expand-card-header[data-type="analogy"] { background: #f59e0b15; color: #f59e0b; }
.expand-card-header[data-type="eli5"] { background: #22c55e15; color: #22c55e; }
.expand-card-body {
  padding: 16px;
  font-size: 0.92rem;
  line-height: 1.8;
  color: var(--text-secondary);
}
.expand-card-body p { margin: 0 0 16px; line-height: 1.85; }
.expand-card-body p:last-child { margin-bottom: 0; }
.expand-card-body ul { margin: 0 0 16px; padding-left: 20px; }
.expand-card-body li { margin-bottom: 6px; line-height: 1.75; }
.expand-card-body strong, .expand-card-body b { color: var(--text-primary); }
.expand-card-body h1, .expand-card-body h2, .expand-card-body h3 {
  color: var(--text-primary);
  font-size: 1rem;
  margin: 16px 0 8px;
}

/* ========== Follow-up Input ========== */
.followup-input-wrap {
  margin-top: 16px;
}
.followup-input-row {
  display: flex;
  align-items: center;
  gap: 0;
  background: var(--bg-input);
  border: 1.5px solid var(--border);
  border-radius: 100px;
  padding: 4px 4px 4px 18px;
  transition: border-color 0.2s;
}
.followup-input-row:focus-within {
  border-color: var(--accent);
}
.followup-input {
  flex: 1;
  border: none;
  background: transparent;
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.88rem;
  padding: 8px 0;
  outline: none;
}
.followup-input::placeholder {
  color: var(--text-muted);
}
.followup-send {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: none;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  flex-shrink: 0;
  transition: background 0.2s, transform 0.1s;
}
.followup-send:hover {
  background: var(--accent-hover);
  transform: scale(1.05);
}
.followup-send:active {
  transform: scale(0.95);
}
.followup-send:disabled {
  opacity: 0.5;
  cursor: wait;
}

/* Question bubble */
.followup-question {
  padding: 10px 16px;
  background: var(--accent);
  color: #fff;
  border-radius: 16px 16px 4px 16px;
  font-size: 0.88rem;
  font-weight: 500;
  line-height: 1.5;
  margin: 12px 0 8px;
  max-width: 85%;
  margin-left: auto;
  width: fit-content;
}

/* ========== AI Tutor Chat ========== */
.tutor-fab {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 16px rgba(99, 102, 241, 0.4);
  z-index: 1000;
  transition: transform 0.2s, box-shadow 0.2s;
}
.tutor-fab:hover { transform: scale(1.08); box-shadow: 0 6px 24px rgba(99, 102, 241, 0.5); }
@media (max-width: 768px) {
  .tutor-fab { bottom: 80px; right: 16px; width: 50px; height: 50px; }
}

.tutor-chat {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 400px;
  max-width: calc(100vw - 32px);
  height: 520px;
  max-height: calc(100vh - 100px);
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 16px;
  display: flex;
  flex-direction: column;
  z-index: 1001;
  box-shadow: 0 8px 32px rgba(0,0,0,0.3);
  overflow: hidden;
  animation: fadeIn 0.2s ease;
}
@media (max-width: 768px) {
  .tutor-chat {
    bottom: 0; right: 0; left: 0;
    width: 100%; max-width: 100%;
    height: calc(100vh - 60px);
    max-height: calc(100vh - 60px);
    border-radius: 16px 16px 0 0;
  }
}

.tutor-chat-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 16px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-card);
}
.tutor-chat-title { font-weight: 700; font-size: 0.95rem; }
.tutor-chat-sub { font-size: 0.72rem; color: var(--text-muted); margin-top: 2px; }
.tutor-header-btn {
  width: 32px; height: 32px;
  border: none; border-radius: 8px;
  background: transparent; color: var(--text-muted);
  cursor: pointer; font-size: 1.1rem;
  display: flex; align-items: center; justify-content: center;
  transition: background 0.15s;
}
.tutor-header-btn:hover { background: var(--bg-hover); color: var(--text-primary); }

.tutor-chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.tutor-msg { display: flex; }
.tutor-msg-user { justify-content: flex-end; }
.tutor-msg-ai { justify-content: flex-start; }

.tutor-msg-bubble {
  max-width: 85%;
  padding: 10px 14px;
  border-radius: 16px;
  font-size: 0.88rem;
  line-height: 1.65;
}
.tutor-msg-user .tutor-msg-bubble {
  background: var(--accent);
  color: #fff;
  border-bottom-right-radius: 4px;
}
.tutor-msg-ai .tutor-msg-bubble {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-bottom-left-radius: 4px;
}
.tutor-msg-ai .tutor-msg-bubble p { margin: 0 0 8px; }
.tutor-msg-ai .tutor-msg-bubble p:last-child { margin: 0; }
.tutor-msg-ai .tutor-msg-bubble strong { color: var(--accent); }

.tutor-msg-typing .tutor-msg-bubble {
  padding: 14px 20px;
}
.tutor-typing-dots { display: flex; gap: 4px; }
.tutor-typing-dots span {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--text-muted);
  animation: tutorBounce 1.2s infinite;
}
.tutor-typing-dots span:nth-child(2) { animation-delay: 0.2s; }
.tutor-typing-dots span:nth-child(3) { animation-delay: 0.4s; }
@keyframes tutorBounce {
  0%, 60%, 100% { transform: translateY(0); }
  30% { transform: translateY(-6px); }
}

.tutor-chat-input {
  display: flex;
  align-items: center;
  gap: 0;
  padding: 10px 10px 10px 18px;
  border-top: 1px solid var(--border);
  background: var(--bg-card);
}
.tutor-chat-input input {
  flex: 1;
  border: none;
  background: transparent;
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.88rem;
  padding: 8px 0;
  outline: none;
}
.tutor-chat-input input::placeholder { color: var(--text-muted); }

/* ========== Course Roadmap ========== */
.roadmap {
  display: flex;
  flex-direction: column;
  gap: 0;
}
.roadmap-step {
  display: flex;
  gap: 16px;
  text-decoration: none;
  color: inherit;
  padding: 4px 0;
  transition: background var(--transition);
  border-radius: var(--radius-sm);
}
.roadmap-step:hover { background: var(--bg-hover); }
.roadmap-marker {
  display: flex;
  flex-direction: column;
  align-items: center;
  min-width: 40px;
}
.roadmap-dot {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.8rem;
  flex-shrink: 0;
  border: 2px solid var(--border);
  background: var(--bg-card);
  color: var(--text-muted);
}
.roadmap-line {
  width: 2px;
  flex: 1;
  min-height: 12px;
  background: var(--border);
}
.roadmap-content {
  padding: 6px 0 16px;
  min-width: 0;
}
.roadmap-title {
  font-weight: 600;
  font-size: 0.9rem;
  line-height: 1.4;
  color: var(--text-primary);
}
.roadmap-sub {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-top: 2px;
}
/* Status colors */
.roadmap-done .roadmap-dot {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
}
.roadmap-done .roadmap-line { background: var(--success); }
.roadmap-active .roadmap-dot {
  background: var(--warning);
  border-color: var(--warning);
  color: #fff;
}
.roadmap-active .roadmap-line { background: var(--warning); }
.roadmap-todo .roadmap-dot {
  border-color: var(--accent);
  color: var(--accent);
}
.roadmap-locked .roadmap-dot {
  opacity: 0.5;
}
.roadmap-locked .roadmap-title { color: var(--text-muted); }

/* ========== Mind Map Fullscreen ========== */
.mindmap-fullscreen {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: var(--bg-primary);
  display: flex;
  flex-direction: column;
  animation: fadeIn 0.2s ease;
}
.mindmap-fullscreen-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-secondary);
}

/* ========== Concept Map ========== */
.concept-map-container {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  position: relative;
}
.concept-map-container svg {
  display: block;
  width: 100%;
}
.concept-map-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
}
.concept-map-header h3 {
  margin: 0;
  font-size: 0.9rem;
  font-weight: 700;
}
.concept-map-legend {
  display: flex;
  gap: 12px;
  font-size: 0.7rem;
  color: var(--text-muted);
}
.concept-map-legend span::before {
  content: '';
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  margin-right: 4px;
  vertical-align: middle;
}
.legend-completed::before { background: var(--success); }
.legend-progress::before { background: var(--warning); }
.legend-notstarted::before { background: var(--text-muted); }
.legend-center::before { background: var(--accent); }
.legend-idea::before { background: #8b5cf6; }
.legend-flashcard::before { background: var(--text-muted); }

/* ========== Course Card Delete ========== */
.course-delete-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-size: 1.2rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  z-index: 2;
  opacity: 0;
}
.card:hover .course-delete-btn { opacity: 1; }
.course-delete-btn:hover {
  background: var(--danger);
  color: #fff;
}

/* ========== Difficulty Selector ========== */
.difficulty-selector {
  display: flex;
  gap: 8px;
}
.difficulty-btn {
  padding: 8px 20px;
  border: 1.5px solid var(--border);
  border-radius: 100px;
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 600;
}
.difficulty-btn:hover { border-color: var(--accent); color: var(--text-primary); }
.difficulty-btn.active {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}

.difficulty-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.7rem;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.difficulty-badge.beginner { background: #22c55e22; color: #22c55e; border: 1px solid #22c55e44; }
.difficulty-badge.intermediate { background: #3b82f622; color: #3b82f6; border: 1px solid #3b82f644; }
.difficulty-badge.advanced { background: #f59e0b22; color: #f59e0b; border: 1px solid #f59e0b44; }

/* ========== Animations ========== */
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.7; }
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

.fade-in { animation: fadeIn 0.4s ease forwards; }

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

.saving-indicator {
  color: var(--text-muted);
  font-size: 0.8rem;
  animation: pulse 1.5s infinite;
}

/* ========== Utilities ========== */
/* ========== Course Library ========== */
.add-course-card {
  border: 2px dashed var(--border);
  background: var(--bg-card);
}

.add-course-card:hover {
  border-color: var(--accent);
}

.course-library-card {
  position: relative;
}

.generation-status {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-top: 20px;
  padding: 16px;
  background: var(--accent-subtle);
  border-radius: var(--radius-md);
  border: 1px solid var(--accent);
}

.generation-spinner {
  width: 32px;
  height: 32px;
  min-width: 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); }
}

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-8 { gap: 8px; }
.gap-12 { gap: 12px; }
.gap-16 { gap: 16px; }
.gap-24 { gap: 24px; }
.mt-8 { margin-top: 8px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mb-32 { margin-bottom: 32px; }
.text-center { text-align: center; }
.text-muted { color: var(--text-muted); }
.text-secondary { color: var(--text-secondary); }
.text-sm { font-size: 0.85rem; }
.font-bold { font-weight: 700; }
.w-full { width: 100%; }
.hidden { display: none !important; }