/* ============================================================
   M.Tech CSE Learning App — Design System
   JNTU Kakinada | Static educational web application
   ============================================================ */

:root {
  /* Base brand */
  --primary: #2563eb;
  --primary-light: #3b82f6;
  --primary-dark: #1d4ed8;

  /* Unit / subject themes */
  --c1: #2563eb;  /* Mathematical Foundations */
  --c2: #7c3aed;  /* Advanced Data Structures */
  --c3: #0891b2;  /* Big Data */
  --c4: #059669;  /* Machine Learning */
  --c5: #d97706;  /* MEAN Stack */
  --c6: #db2777;  /* electives */
  --c7: #4f46e5;
  --c8: #0f766e;

  /* Semantics */
  --bg-body: #f6f7fb;
  --bg-card: #ffffff;
  --bg-hover: #eef2ff;
  --bg-muted: #f1f5f9;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --border-light: #e2e8f0;
  --border-medium: #cbd5e1;

  /* Status */
  --success: #16a34a;
  --success-bg: #dcfce7;
  --danger: #dc2626;
  --danger-bg: #fee2e2;
  --warning: #d97706;
  --warning-bg: #fef3c7;
  --info-bg: #dbeafe;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;

  /* Typography */
  --font-sans: 'Inter', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', ui-monospace, monospace;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(15,23,42,0.06);
  --shadow-md: 0 4px 12px rgba(15,23,42,0.08);
  --shadow-lg: 0 12px 24px rgba(15,23,42,0.12);

  /* Transitions */
  --t-fast: 150ms ease;
  --t-normal: 250ms ease;
  --t-slow: 350ms ease;

  --nav-h: 64px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background: var(--bg-body);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

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

h1,h2,h3,h4 { line-height: 1.25; color: var(--text-primary); font-weight: 700; }
h1 { font-size: 1.8rem; }
h2 { font-size: 1.35rem; }
h3 { font-size: 1.1rem; }
h4 { font-size: 1rem; }

p { color: var(--text-primary); }

ul, ol { padding-left: 1.4rem; }

main { flex: 1; }

/* ============ Buttons ============ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.55rem 1.1rem;
  border-radius: var(--radius-md);
  border: 1.5px solid transparent;
  font-weight: 600;
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all var(--t-fast);
  line-height: 1.2;
}
.btn:active { transform: translateY(1px); }

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

.btn-secondary { background: var(--bg-muted); color: var(--text-primary); border-color: var(--border-medium); }
.btn-secondary:hover { background: var(--border-light); }

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

.btn-success { background: var(--success); color: #fff; border-color: var(--success); }
.btn-success:hover { filter: brightness(0.92); }

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

.btn-sm { padding: 0.35rem 0.8rem; font-size: 0.8rem; }
.btn-lg { padding: 0.8rem 1.6rem; font-size: 1rem; }

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

/* ============ Navigation ============ */
.main-nav {
  position: sticky;
  top: 0;
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  padding: 0 var(--space-xl);
  height: var(--nav-h);
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-light);
}

.nav-brand a {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 800;
  font-size: 1.05rem;
  color: var(--primary);
}
.nav-brand .brand-icon {
  width: 36px; height: 36px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, var(--primary), var(--c6));
  color: #fff; border-radius: var(--radius-md);
  font-size: 1.05rem;
}
.nav-brand small { display: block; font-size: 0.65rem; font-weight: 600; color: var(--text-muted); letter-spacing: 0.04em; }

.nav-links { display: flex; align-items: center; gap: 0.25rem; }
.nav-link {
  display: inline-flex; align-items: center; gap: 0.45rem;
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-weight: 600; font-size: 0.9rem;
  transition: all var(--t-fast);
}
.nav-link:hover { background: var(--bg-hover); color: var(--primary); }
.nav-link.active { background: var(--primary); color: #fff; }

.nav-progress { display: flex; align-items: center; gap: 0.6rem; font-weight: 700; font-size: 0.9rem; color: var(--primary); }
.nav-toggle { display: none; background: none; border: none; font-size: 1.4rem; color: var(--text-primary); cursor: pointer; }

/* ============ Hero ============ */
.hero {
  background: linear-gradient(135deg, #1e3a8a 0%, #2563eb 55%, #4f46e5 100%);
  color: #fff;
  padding: var(--space-2xl) var(--space-xl);
  text-align: center;
}
.hero h1 { color: #fff; font-size: 2.1rem; margin-bottom: 0.5rem; }
.hero p { color: rgba(255,255,255,0.9); max-width: 640px; margin: 0 auto; font-size: 1.05rem; }
.hero .badge-pill {
  display: inline-block;
  background: rgba(255,255,255,0.18);
  border: 1px solid rgba(255,255,255,0.3);
  color: #fff;
  padding: 0.3rem 0.9rem;
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 600;
  margin-bottom: 0.8rem;
}
.hero .hero-stats {
  display: flex; justify-content: center; gap: var(--space-xl);
  margin-top: var(--space-xl);
  flex-wrap: wrap;
}
.hero .stat { text-align: center; }
.hero .stat .num { font-size: 1.6rem; font-weight: 800; }
.hero .stat .lbl { font-size: 0.8rem; opacity: 0.85; }

/* ============ Container / Layout ============ */
.container { width: 100%; max-width: 1200px; margin: 0 auto; padding: var(--space-xl); }
.container-narrow { max-width: 860px; }

.section-title {
  display: flex; align-items: center; gap: 0.6rem;
  font-size: 1.4rem;
  margin: var(--space-xl) 0 var(--space-lg);
}
.section-title i { color: var(--primary); }

/* ============ Card Grid ============ */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.4rem;
}

/* ============ Cards ============ */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  box-shadow: var(--shadow-sm);
  transition: transform var(--t-normal), box-shadow var(--t-normal), border-color var(--t-normal);
  position: relative;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); border-color: var(--border-medium); }

.unit-card { cursor: pointer; }
.unit-card.locked { opacity: 0.6; cursor: not-allowed; }
.unit-card.completed { border-color: var(--success); }
.unit-card.completed::after {
  content: '\f00c'; font-family: 'Font Awesome 6 Free'; font-weight: 900;
  position: absolute; top: 0.9rem; right: 0.9rem;
  background: var(--success); color: #fff;
  width: 26px; height: 26px; border-radius: var(--radius-full);
  display: grid; place-items: center; font-size: 0.75rem;
}

.card-icon {
  width: 52px; height: 52px;
  border-radius: var(--radius-md);
  display: grid; place-items: center;
  font-size: 1.4rem;
  color: #fff;
  margin-bottom: var(--space-md);
}
.card-icon.c-1 { background: linear-gradient(135deg, var(--c1), #60a5fa); }
.card-icon.c-2 { background: linear-gradient(135deg, var(--c2), #a78bfa); }
.card-icon.c-3 { background: linear-gradient(135deg, var(--c3), #22d3ee); }
.card-icon.c-4 { background: linear-gradient(135deg, var(--c4), #34d399); }
.card-icon.c-5 { background: linear-gradient(135deg, var(--c5), #fbbf24); }

.card h3 { margin-bottom: 0.35rem; }
.card .sub { color: var(--text-secondary); font-size: 0.85rem; margin-bottom: var(--space-md); }
.card .tags { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.tag {
  font-size: 0.72rem; font-weight: 600;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
  background: var(--bg-muted); color: var(--text-secondary);
}
.tag.core { background: var(--info-bg); color: var(--primary-dark); }
.tag.elec { background: var(--warning-bg); color: var(--warning); }
.tag.lab { background: #f3e8ff; color: #7c3aed; }

/* ============ Breadcrumb ============ */
.breadcrumb {
  display: flex; align-items: center; gap: 0.5rem;
  font-size: 0.85rem; color: var(--text-muted);
  padding: var(--space-md) var(--space-xl) 0;
  flex-wrap: wrap;
}
.breadcrumb a { color: var(--text-secondary); font-weight: 500; }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb .sep { color: var(--border-medium); }

/* ============ Unit / Subject header ============ */
.unit-header {
  padding: var(--space-xl);
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-light);
}
.unit-header .unit-badge {
  display: inline-block;
  background: var(--unit-color, var(--primary));
  color: #fff;
  font-weight: 700;
  font-size: 0.8rem;
  padding: 0.3rem 0.9rem;
  border-radius: var(--radius-full);
  letter-spacing: 0.03em;
  margin-bottom: var(--space-sm);
}
.unit-header h1 { font-size: 1.8rem; margin-bottom: 0.3rem; }
.unit-header .unit-subtitle { color: var(--text-secondary); max-width: 720px; }
.unit-header .meta {
  display: flex; flex-wrap: wrap; gap: var(--space-lg);
  margin-top: var(--space-md); font-size: 0.85rem; color: var(--text-secondary);
}
.unit-header .meta i { margin-right: 0.35rem; color: var(--primary); }

/* ============ Content sections ============ */
.content-container { padding: var(--space-xl); max-width: 900px; margin: 0 auto; }

.content-section {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin-bottom: var(--space-lg);
  box-shadow: var(--shadow-sm);
}
.content-section h2 { display: flex; align-items: center; gap: 0.6rem; margin-bottom: var(--space-md); }
.content-section h2 i { color: var(--unit-color, var(--primary)); }
.content-section h3 { margin: var(--space-lg) 0 var(--space-sm); }
.content-section h3 i { color: var(--unit-color, var(--primary)); margin-right: 0.4rem; }

.content-section p, .content-section li { color: var(--text-primary); }
.content-section ul, .content-section ol { margin: var(--space-sm) 0; }

/* Key points / info boxes */
.key-points {
  background: var(--warning-bg);
  border-left: 4px solid var(--warning);
  border-radius: var(--radius-md);
  padding: var(--space-md) var(--space-lg);
  margin: var(--space-lg) 0;
}
.key-points h3 { margin: 0 0 var(--space-sm) 0; color: var(--warning); }
.key-points h3 i { margin-right: 0.35rem; }
.key-points ul { margin: 0; }

.info-box {
  background: var(--info-bg);
  border-left: 4px solid var(--primary);
  border-radius: var(--radius-md);
  padding: var(--space-md) var(--space-lg);
  margin: var(--space-md) 0;
}
.info-box h3 { margin: 0 0 0.4rem; color: var(--primary-dark); }
.info-box h3 i { margin-right: 0.35rem; }

.success-box {
  background: var(--success-bg);
  border-left: 4px solid var(--success);
  border-radius: var(--radius-md);
  padding: var(--space-md) var(--space-lg);
  margin: var(--space-md) 0;
}
.success-box h3 { margin: 0 0 0.4rem; color: var(--success); }
.success-box h3 i { margin-right: 0.35rem; }

/* ============ Mermaid diagram ============ */
.diagram-wrapper {
  position: relative;
  margin: var(--space-lg) 0;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  background: var(--bg-card);
  overflow: auto;
}
.diagram-controls {
  position: absolute; top: 0.5rem; right: 0.5rem;
  display: flex; gap: 0.25rem; z-index: 10;
}
.diagram-controls button {
  width: 2rem; height: 2rem;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  cursor: pointer;
  transition: all var(--t-fast);
  color: var(--text-secondary);
}
.diagram-controls button:hover { background: var(--primary); color: #fff; border-color: var(--primary); }
.diagram-container { display: flex; justify-content: center; min-height: 120px; transform-origin: top left; transition: transform var(--t-normal); }
.mermaid { margin: 0; }

/* ============ Tables ============ */
.table-wrap { overflow-x: auto; margin: var(--space-md) 0; }
table.data-table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
table.data-table th, table.data-table td { text-align: left; padding: 0.6rem 0.8rem; border-bottom: 1px solid var(--border-light); }
table.data-table thead th { background: var(--bg-muted); font-weight: 700; color: var(--text-secondary); }
table.data-table tbody tr:hover { background: var(--bg-hover); }

/* ============ Progress ============ */
.progress-wrapper { margin-bottom: var(--space-md); }
.progress-bar {
  height: 12px; background: var(--bg-muted);
  border-radius: var(--radius-full);
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--c4));
  border-radius: var(--radius-full);
  transition: width var(--t-normal);
  width: 0;
}
.progress-text { display: flex; justify-content: space-between; margin-top: 0.4rem; font-size: 0.85rem; color: var(--text-secondary); }

.progress-ring {
  --pg: 0;
  width: 72px; height: 72px; border-radius: 50%;
  background: conic-gradient(var(--primary) calc(var(--pg) * 1%), var(--bg-muted) 0);
  display: grid; place-items: center;
  position: relative;
}
.progress-ring::before { content: ''; position: absolute; inset: 8px; border-radius: 50%; background: var(--bg-card); }
.progress-ring span { position: relative; font-weight: 800; font-size: 0.9rem; }

/* ============ Topic / component navigation ============ */
.topic-toc {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
}
.topic-toc h3 { margin-bottom: var(--space-md); display: flex; align-items: center; gap: 0.5rem; }
.topic-toc h3 i { color: var(--unit-color, var(--primary)); }
.topic-list { list-style: none; padding: 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(250px,1fr)); gap: 0.6rem; }
.topic-list li a {
  display: flex; align-items: center; gap: 0.6rem;
  padding: 0.65rem 0.9rem;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-weight: 600; font-size: 0.9rem;
  transition: all var(--t-fast);
}
.topic-list li a:hover { border-color: var(--unit-color, var(--primary)); background: var(--bg-hover); color: var(--unit-color, var(--primary)); }
.topic-list li a .num { background: var(--unit-color, var(--primary)); color: #fff; width: 26px; height: 26px; border-radius: var(--radius-sm); display: grid; place-items: center; font-size: 0.75rem; flex-shrink: 0; }

/* ============ Quiz / Activity ============ */
.activity-container { max-width: 820px; margin: 0 auto; padding: var(--space-xl); }
.activity-header { text-align: center; margin-bottom: var(--space-lg); }
.activity-header h1 { display: flex; align-items: center; justify-content: center; gap: 0.6rem; margin-bottom: 0.3rem; }
.activity-header h1 i { color: var(--primary); }
.activity-header p { color: var(--text-secondary); }

.quiz-container { margin-top: var(--space-md); }
.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-sm);
  animation: fadeIn 0.3s ease forwards;
}
.q-count { font-size: 0.8rem; color: var(--text-muted); font-weight: 700; margin-bottom: 0.5rem; }
.question-text { font-size: 1.1rem; font-weight: 700; margin-bottom: var(--space-lg); }

.options { display: flex; flex-direction: column; gap: 0.6rem; }
.option-btn {
  display: flex; align-items: center; gap: 0.7rem;
  width: 100%;
  padding: 0.8rem 1rem;
  border: 1.5px solid var(--border-light);
  border-radius: var(--radius-md);
  background: var(--bg-card);
  cursor: pointer;
  font-family: inherit; font-size: 0.95rem; color: var(--text-primary);
  text-align: left;
  transition: all var(--t-fast);
}
.option-btn:hover:not(:disabled) { border-color: var(--primary); background: var(--bg-hover); }
.option-btn .option-letter {
  width: 28px; height: 28px; flex-shrink: 0;
  border-radius: var(--radius-full);
  background: var(--bg-muted);
  display: grid; place-items: center;
  font-weight: 800; font-size: 0.8rem;
}
.option-btn.selected { border-color: var(--primary); background: var(--info-bg); }
.option-btn.selected .option-letter { background: var(--primary); color: #fff; }
.option-btn.correct { border-color: var(--success); background: var(--success-bg); }
.option-btn.correct .option-letter { background: var(--success); color: #fff; }
.option-btn.incorrect { border-color: var(--danger); background: var(--danger-bg); }
.option-btn.incorrect .option-letter { background: var(--danger); color: #fff; }
.option-btn:disabled { cursor: not-allowed; }

.explanation {
  margin-top: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-muted);
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  animation: fadeIn 0.3s ease;
}
.explanation strong { color: var(--primary-dark); }

.quiz-nav { display: flex; justify-content: space-between; gap: var(--space-md); margin-top: var(--space-lg); }
.quiz-nav .btn { flex: 1; justify-content: center; }
.quiz-nav .btn:disabled { opacity: 0.45; }

/* Results */
.results-panel {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-2xl);
  text-align: center;
  box-shadow: var(--shadow-md);
  animation: scaleIn 0.4s ease;
}
.results-score { margin-bottom: var(--space-md); }
.score-number { font-size: 3.4rem; font-weight: 800; color: var(--primary); }
.score-total { font-size: 1.6rem; color: var(--text-muted); font-weight: 600; }
.results-percent { font-size: 1rem; color: var(--text-secondary); margin-bottom: var(--space-md); }
.results-message { font-size: 1.05rem; margin-bottom: var(--space-lg); }
.results-message .fa-trophy { color: var(--warning); }
.results-message .fa-medal { color: var(--primary); }
.results-actions { display: flex; justify-content: center; gap: var(--space-md); flex-wrap: wrap; }
.results-ring { margin: 0 auto var(--space-md); width: 120px; height: 120px; --pg: 0; }
.results-ring::before { inset: 12px; }
.results-ring span { font-size: 1.3rem; }

/* ============ PYQ / repeated questions ============ */
.pyq-stage {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
  box-shadow: var(--shadow-sm);
}
.pyq-stage h2 { display: flex; align-items: center; gap: 0.6rem; margin-bottom: var(--space-md); font-size: 1.1rem; }
.pyq-stage h2 .stage-badge {
  background: var(--warning); color: #fff; font-size: 0.7rem; font-weight: 700;
  padding: 0.2rem 0.6rem; border-radius: var(--radius-full);
}
.pyq-stage h2 i { color: var(--warning); }
.pyq-item {
  padding: var(--space-md);
  border-left: 3px solid var(--border-medium);
  margin-bottom: var(--space-sm);
  background: var(--bg-body);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}
.pyq-item.frequent { border-left-color: var(--danger); }
.pyq-item .freq-badge {
  display: inline-block;
  background: var(--danger-bg); color: var(--danger);
  font-size: 0.68rem; font-weight: 800;
  padding: 0.15rem 0.5rem;
  border-radius: var(--radius-full);
  margin-bottom: 0.35rem;
}
.pyq-item .q { font-weight: 600; }
.pyq-item .marks { font-size: 0.75rem; color: var(--text-muted); margin-top: 0.2rem; }

/* ============ Accordion ============ */
.accordion-item { border: 1px solid var(--border-light); border-radius: var(--radius-md); margin-bottom: 0.6rem; overflow: hidden; background: var(--bg-card); }
.accordion-btn {
  width: 100%; display: flex; align-items: center; justify-content: space-between;
  padding: 0.9rem 1.1rem;
  background: none; border: none;
  font-family: inherit; font-size: 0.95rem; font-weight: 700; color: var(--text-primary);
  cursor: pointer; text-align: left;
}
.accordion-btn:hover { background: var(--bg-hover); }
.accordion-btn i.fa-chevron-down { transition: transform var(--t-normal); color: var(--text-muted); }
.accordion-item.open .accordion-btn i.fa-chevron-down { transform: rotate(180deg); }
.accordion-body { display: none; padding: 0 var(--space-lg) var(--space-lg); }
.accordion-item.open .accordion-body { display: block; animation: fadeIn 0.25s ease; }

/* ============ Glossaray / grid ============ */
.glossary-search { margin-bottom: var(--space-lg); }
.glossary-search input {
  width: 100%; max-width: 480px;
  padding: 0.7rem 1rem;
  border: 1.5px solid var(--border-light);
  border-radius: var(--radius-md);
  font-family: inherit; font-size: 0.95rem;
}
.glossary-search input:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--info-bg); }

/* ============ Footer ============ */
.site-footer {
  border-top: 1px solid var(--border-light);
  background: var(--bg-card);
  padding: var(--space-lg) var(--space-xl);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: var(--space-2xl);
}
.site-footer a { color: var(--text-secondary); }
.site-footer a:hover { color: var(--primary); }

/* ============ Unit nav (prev/next) ============ */
.unit-nav {
  display: flex; justify-content: space-between; gap: var(--space-md);
  padding: 0 var(--space-xl) var(--space-xl);
  max-width: 900px; margin: 0 auto;
  flex-wrap: wrap;
}
.unit-nav .nav-group { display: flex; gap: var(--space-md); }

/* ============ Toast ============ */
.toast-container { position: fixed; top: 72px; right: 20px; z-index: 9999; display: flex; flex-direction: column; gap: 0.6rem; }
.toast {
  background: var(--text-primary); color: #fff;
  padding: 0.7rem 1.1rem;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  font-size: 0.9rem;
  animation: slideInRight 0.3s ease;
  display: flex; align-items: center; gap: 0.5rem;
}
.toast.success { background: var(--success); }
.toast.error { background: var(--danger); }
.toast.info { background: var(--primary); }
.toast.fade-out { opacity: 0; transition: opacity 0.3s ease; }

/* ============ Confetti ============ */
#confetti-container {
  position: fixed; inset: 0; pointer-events: none;
  z-index: 9998; overflow: hidden;
}
.confetti-piece {
  position: absolute; top: -20px;
  width: 10px; height: 16px;
  border-radius: 2px;
  animation: confettiFall linear forwards;
  will-change: transform, opacity;
}

/* ============ Animations ============ */
@keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }
@keyframes slideInRight { from { opacity: 0; transform: translateX(30px); } to { opacity: 1; transform: translateX(0); } }
@keyframes slideInLeft { from { opacity: 0; transform: translateX(-30px); } to { opacity: 1; transform: translateX(0); } }
@keyframes scaleIn { from { opacity: 0; transform: scale(0.92); } to { opacity: 1; transform: scale(1); } }
@keyframes confettiFall {
  0%   { transform: translateY(-5vh)   rotate(0deg);   opacity: 1; }
  100% { transform: translateY(110vh)  rotate(720deg); opacity: 0.7; }
}
@keyframes pulse { 0%,100% { transform: scale(1); } 50% { transform: scale(1.05); } }
@keyframes floaty { 0%,100% { transform: translateY(0); } 50% { transform: translateY(-8px); } }

.animate-fadeIn { animation: fadeIn 0.3s ease forwards; }
.animate-slideIn { animation: slideInRight 0.3s ease forwards; }
.animate-pulse { animation: pulse 2s ease infinite; }

/* ============ Utility ============ */
.text-center { text-align: center; }
.mt-0 { margin-top: 0; } .mt-1 { margin-top: var(--space-sm); } .mt-2 { margin-top: var(--space-md); }
.mt-3 { margin-top: var(--space-lg); } .mt-4 { margin-top: var(--space-xl); }
.mb-2 { margin-bottom: var(--space-md); } .mb-3 { margin-bottom: var(--space-lg); }
.gap-2 { gap: var(--space-md); }
.flex-col { display: flex; flex-direction: column; gap: var(--space-md); }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-lg); }
.muted { color: var(--text-secondary); }
.small { font-size: 0.85rem; }
strong, b { font-weight: 700; }

code, .code {
  font-family: var(--font-mono);
  background: var(--bg-muted);
  padding: 0.15rem 0.4rem;
  border-radius: var(--radius-sm);
  font-size: 0.85em;
}
pre.code-block {
  background: #0f172a; color: #e2e8f0;
  padding: var(--space-lg);
  border-radius: var(--radius-md);
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 1.6;
  margin: var(--space-md) 0;
}
pre.code-block .tok-k { color: #c084fc; }
pre.code-block .tok-s { color: #86efac; }
pre.code-block .tok-c { color: #64748b; font-style: italic; }
pre.code-block .tok-n { color: #67e8f9; }
pre.code-block .tok-f { color: #fbbf24; }

/* ============ Responsive ============ */
@media (max-width: 900px) {
  .nav-links { display: none; position: absolute; top: var(--nav-h); left: 0; right: 0;
    background: var(--bg-card); flex-direction: column; padding: var(--space-md);
    border-bottom: 1px solid var(--border-light); box-shadow: var(--shadow-md); gap: 0.4rem; }
  .nav-links.open { display: flex; }
  .nav-toggle { display: block; }
  .card-grid { grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
  .grid-2 { grid-template-columns: 1fr; }
  .hero h1 { font-size: 1.6rem; }
}

@media (max-width: 600px) {
  .card-grid { grid-template-columns: 1fr; }
  .container, .content-container, .activity-container { padding: var(--space-md); }
  .unit-header, .content-section { padding: var(--space-lg); }
  .content-section { padding: var(--space-md); }
  .topic-list { grid-template-columns: 1fr; }
  .results-actions { flex-direction: column; }
  .results-actions .btn { width: 100%; justify-content: center; }
  .hero { padding: var(--space-xl) var(--space-md); }
  .hero .hero-stats { gap: var(--space-lg); }
  .unit-nav { flex-direction: column; }
  .quiz-nav .btn { font-size: 0.85rem; }
}

/* ═══════════════════════════════════════════════════════════════
   CELEBOT AI ASSISTANT WIDGET
   ═══════════════════════════════════════════════════════════════ */

:root {
  --celebot: #34d399;
  --celebot-dark: #059669;
  --celebot-glow: rgba(52, 211, 153, 0.2);
  --cw-bg: #ffffff;
  --cw-bg2: #f8fafc;
  --cw-border: #e2e8f0;
  --cw-text: #1e293b;
  --cw-text2: #64748b;
  --cw-msg-user: #eff6ff;
  --cw-msg-bot: #f0fdf4;
}

.celebot-fab {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--celebot), var(--celebot-dark));
  color: #fff;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  box-shadow: 0 4px 20px var(--celebot-glow), 0 2px 8px rgba(0,0,0,0.15);
  z-index: 9999;
  transition: transform 0.2s, box-shadow 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}
.celebot-fab:hover {
  transform: scale(1.1);
  box-shadow: 0 6px 28px var(--celebot-glow), 0 4px 12px rgba(0,0,0,0.2);
}
.celebot-fab.open {
  transform: rotate(90deg) scale(0.9);
  background: linear-gradient(135deg, #ef4444, #dc2626);
}

.celebot-widget {
  position: fixed;
  bottom: 5.5rem;
  right: 1.5rem;
  width: 400px;
  max-width: calc(100vw - 2rem);
  height: 560px;
  max-height: calc(100vh - 8rem);
  background: var(--cw-bg);
  border-radius: 16px;
  box-shadow: 0 12px 48px rgba(0,0,0,0.15), 0 0 0 1px var(--cw-border);
  z-index: 9998;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  opacity: 0;
  transform: translateY(20px) scale(0.95);
  pointer-events: none;
  transition: opacity 0.25s, transform 0.25s;
}
.celebot-widget.open {
  opacity: 1;
  transform: translateY(0) scale(1);
  pointer-events: auto;
}

.cw-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 1rem;
  background: linear-gradient(135deg, var(--celebot), var(--celebot-dark));
  color: #fff;
}
.cw-header-left {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.cw-icon {
  font-size: 1.3rem;
  animation: cw-pulse 2s ease-in-out infinite;
}
@keyframes cw-pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}
.cw-title { font-weight: 700; font-size: 0.95rem; }
.cw-subtitle { font-size: 0.7rem; opacity: 0.85; }
.cw-header-actions { display: flex; gap: 0.3rem; }
.cw-btn-icon {
  background: rgba(255,255,255,0.15);
  border: none;
  color: #fff;
  width: 30px;
  height: 30px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.8rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s;
}
.cw-btn-icon:hover { background: rgba(255,255,255,0.3); }

.cw-api-bar {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 0.75rem;
  background: var(--cw-bg2);
  border-bottom: 1px solid var(--cw-border);
}
.cw-api-bar input {
  flex: 1;
  padding: 0.35rem 0.6rem;
  border: 1px solid var(--cw-border);
  border-radius: 6px;
  font-size: 0.75rem;
  background: var(--cw-bg);
  color: var(--cw-text);
}
.cw-api-save {
  background: var(--celebot);
  color: #fff;
  border: none;
  border-radius: 6px;
  padding: 0.35rem 0.6rem;
  cursor: pointer;
  font-size: 0.75rem;
}
.cw-api-status {
  font-size: 0.65rem;
  color: var(--cw-text2);
}

.cw-messages {
  flex: 1;
  overflow-y: auto;
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.cw-msg {
  max-width: 88%;
  padding: 0.6rem 0.8rem;
  border-radius: 12px;
  font-size: 0.82rem;
  line-height: 1.5;
  word-break: break-word;
}
.cw-bot {
  align-self: flex-start;
  background: var(--cw-msg-bot);
  border: 1px solid #dcfce7;
  border-bottom-left-radius: 4px;
}
.cw-user {
  align-self: flex-end;
  background: var(--cw-msg-user);
  border: 1px solid #bfdbfe;
  border-bottom-right-radius: 4px;
}
.cw-msg-label {
  font-size: 0.65rem;
  font-weight: 600;
  color: var(--celebot-dark);
  margin-bottom: 0.2rem;
  display: flex;
  align-items: center;
  gap: 0.3rem;
}
.cw-user .cw-msg-label { color: #2563eb; }
.cw-msg-body { color: var(--cw-text); }
.cw-msg-body code {
  background: rgba(0,0,0,0.06);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  font-size: 0.78rem;
  font-family: 'JetBrains Mono', monospace;
}
.cw-msg-body pre {
  background: #1e293b;
  color: #e2e8f0;
  padding: 0.6rem;
  border-radius: 8px;
  overflow-x: auto;
  font-size: 0.75rem;
  margin: 0.4rem 0;
  font-family: 'JetBrains Mono', monospace;
}

.cw-think {
  background: #fefce8;
  border: 1px solid #fde68a;
  border-radius: 8px;
  padding: 0.5rem 0.7rem;
  margin-bottom: 0.4rem;
  font-size: 0.75rem;
  color: #92400e;
}
.cw-think-label {
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.3rem;
}
.cw-think-body {
  margin-top: 0.3rem;
  display: none;
  white-space: pre-wrap;
}
.cw-think.open .cw-think-body { display: block; }

.cw-skills {
  display: flex;
  gap: 0.3rem;
  padding: 0.4rem 0.75rem;
  overflow-x: auto;
  border-top: 1px solid var(--cw-border);
  background: var(--cw-bg2);
}
.cw-skill {
  flex-shrink: 0;
  padding: 0.3rem 0.6rem;
  border: 1px solid var(--celebot);
  border-radius: 20px;
  background: transparent;
  color: var(--celebot-dark);
  font-size: 0.7rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s;
  white-space: nowrap;
  display: flex;
  align-items: center;
  gap: 0.25rem;
}
.cw-skill:hover {
  background: var(--celebot);
  color: #fff;
}

.cw-input-row {
  display: flex;
  gap: 0.4rem;
  padding: 0.6rem 0.75rem;
  border-top: 1px solid var(--cw-border);
  background: var(--cw-bg);
}
.cw-input-row input {
  flex: 1;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--cw-border);
  border-radius: 24px;
  font-size: 0.82rem;
  outline: none;
  transition: border-color 0.15s;
  color: var(--cw-text);
}
.cw-input-row input:focus { border-color: var(--celebot); }
.cw-send {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: var(--celebot);
  color: #fff;
  border: none;
  cursor: pointer;
  font-size: 0.85rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s;
  flex-shrink: 0;
}
.cw-send:hover { background: var(--celebot-dark); }
.cw-send:disabled { opacity: 0.5; cursor: not-allowed; }

/* Config Modal */
.cw-config-modal {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 10000;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s;
}
.cw-config-modal.open {
  opacity: 1;
  pointer-events: auto;
}
.cw-config-card {
  background: var(--cw-bg);
  border-radius: 16px;
  padding: 1.5rem;
  width: 380px;
  max-width: 90vw;
  box-shadow: 0 20px 60px rgba(0,0,0,0.2);
}
.cw-config-card h3 {
  font-size: 1rem;
  margin-bottom: 1rem;
  color: var(--celebot-dark);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.cw-cfg-field {
  margin-bottom: 0.75rem;
}
.cw-cfg-field label {
  display: block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--cw-text2);
  margin-bottom: 0.3rem;
}
.cw-cfg-field select,
.cw-cfg-field input,
.cw-cfg-field textarea {
  width: 100%;
  padding: 0.45rem 0.6rem;
  border: 1px solid var(--cw-border);
  border-radius: 8px;
  font-size: 0.8rem;
  background: var(--cw-bg);
  color: var(--cw-text);
}
.cw-cfg-field textarea { resize: vertical; }
.cw-cfg-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
}
.cw-cfg-actions {
  display: flex;
  gap: 0.5rem;
  margin-top: 1rem;
}
.cw-cfg-actions button {
  flex: 1;
  padding: 0.5rem;
  border-radius: 8px;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid var(--cw-border);
  background: var(--cw-bg2);
  color: var(--cw-text);
}
.cw-cfg-save {
  background: var(--celebot) !important;
  color: #fff !important;
  border: none !important;
}

@media (max-width: 480px) {
  .celebot-widget {
    bottom: 0;
    right: 0;
    width: 100vw;
    max-width: 100vw;
    height: 100vh;
    max-height: 100vh;
    border-radius: 0;
  }
  .celebot-fab {
    bottom: 1rem;
    right: 1rem;
    width: 50px;
    height: 50px;
    font-size: 1.2rem;
  }
}