/* =========================================================
   Spark Learning – Design System
   ========================================================= */

/* ── CSS Variables ── */
:root {
  --primary:     #2C3E50;
  --secondary:   #48C9B0;
  --accent:      #F4D03F;
  --success:     #2ECC71;
  --error:       #FF6B6B;
  --bg:          #F8F9FA;
  --bg-card:     #FFFFFF;
  --text:        #212529;
  --text-muted:  #6C757D;
  --border:      #DEE2E6;
  --radius:      14px;
  --shadow:      0 4px 20px rgba(0,0,0,0.08);
  --shadow-lg:   0 8px 40px rgba(0,0,0,0.12);
  --transition:  0.25s ease;
  --header-h:    64px;

  /* Contrast text on colored backgrounds */
  --on-primary:  #fff;
  --on-accent:   #1a1a1a;
  --on-success:  #fff;
  --on-error:    #fff;

  /* Spacing scale */
  --space-xs:  4px;
  --space-sm:  8px;
  --space-md:  16px;
  --space-lg:  24px;
  --space-xl:  32px;
  --space-2xl: 48px;

  /* Z-index scale */
  --z-header:     100;
  --z-scroll-top: 200;
  --z-toast:      300;
  --z-confetti:   400;
  --z-skip:       500;

  /* Border widths */
  --border-width:    1px;
  --border-width-lg: 2px;
}

[data-theme="dark"] {
  --primary:     #8AB4F8;
  --secondary:   #3A8979;
  --accent:      #D4AC0D;
  --error:       #D65A5A;
  --bg:          #121212;
  --bg-card:     #1E1E1E;
  --text:        #E9ECEF;
  --text-muted:  #ADB5BD;
  --border:      #2C2C2C;
  --shadow:      0 4px 20px rgba(0,0,0,0.3);
  --shadow-lg:   0 8px 40px rgba(0,0,0,0.5);
  --on-primary:  #121212;
  --on-accent:   #121212;
  --on-success:  #121212;
  --on-error:    #121212;
}

/* ── Accessibility ── */
.skip-to-content {
  position: absolute;
  top: -100%;
  left: 16px;
  z-index: var(--z-skip);
  padding: 12px 24px;
  background: var(--primary);
  color: var(--on-primary);
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
  transition: top 0.2s ease;
}
.skip-to-content:focus {
  top: 12px;
}

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

:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}
:focus:not(:focus-visible) {
  outline: none;
}

.tab-btn:focus-visible { outline-offset: -2px; border-radius: 4px; }
.module-card:focus-visible { outline-offset: 2px; box-shadow: var(--shadow-lg); }
.level-card:focus-visible { outline-offset: 4px; }
.keyword-tag:focus-visible { outline-offset: 2px; }
.search-clear:focus-visible { outline-offset: 2px; }

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

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  transition: background var(--transition), color var(--transition);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

h1, h2, h3, h4, h5, h6 {
  font-family: 'Poppins', sans-serif;
  font-weight: 700;
  line-height: 1.25;
}

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

button { cursor: pointer; border: none; background: none; font-family: inherit; font-size: inherit; }

a { color: inherit; text-decoration: none; }

main { flex: 1; }

/* ── Layout ── */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ── Header ── */
.header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  height: var(--header-h);
  background: rgba(var(--bg-rgb, 248,249,250), 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}

/* Hack for rgba variable */
[data-theme="light"] .header { background: rgba(248,249,250,0.85); }
[data-theme="dark"]  .header { background: rgba(18,18,18,0.9); }

.header-inner {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  height: var(--header-h);
}

/* ── Logo ── */
.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  flex-shrink: 0;
}

.logo-img {
  height: 36px;
  width: auto;
  border-radius: 6px;
  object-fit: contain;
}

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

.logo-text {
  font-family: 'Poppins', sans-serif;
  font-weight: 800;
  font-size: 1.25rem;
  white-space: nowrap;
}

.logo-spark    { color: var(--primary); }
.logo-learning { color: var(--accent); }

/* ── Nav ── */
.nav {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
}

.nav-link {
  padding: 8px 16px;
  border-radius: var(--radius);
  font-weight: 500;
  color: var(--text-muted);
  transition: color var(--transition), background var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary);
  background: color-mix(in srgb, var(--primary) 8%, transparent);
}

/* ── Theme Toggle ── */
.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  transition: transform var(--transition), background var(--transition);
  flex-shrink: 0;
}

.theme-toggle:hover { transform: rotate(20deg); }

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition), opacity var(--transition);
  border: 2px solid transparent;
  line-height: 1;
  white-space: nowrap;
}

.btn:hover { transform: translateY(-2px); box-shadow: var(--shadow); }
.btn:active { transform: translateY(0); }

.btn-primary {
  background: var(--accent);
  color: var(--on-accent);
  border-color: var(--accent);
}
.btn-primary:hover { box-shadow: 0 6px 20px rgba(244,208,63,0.4); }

.btn-secondary {
  background: transparent;
  color: var(--primary);
  border-color: var(--primary);
}
.btn-secondary:hover { background: color-mix(in srgb, var(--primary) 8%, transparent); }

.btn-success {
  background: var(--success);
  color: var(--on-success);
  border-color: var(--success);
}

.btn-hint {
  background: color-mix(in srgb, var(--secondary) 15%, transparent);
  color: var(--secondary);
  border-color: var(--secondary);
  font-size: 0.85rem;
  padding: 8px 16px;
}
.btn-hint:hover { background: color-mix(in srgb, var(--secondary) 25%, transparent); }

.btn-sm { padding: 8px 16px; font-size: 0.875rem; }

/* ── Badge / Pill ── */
.badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 100px;
  font-size: 0.75rem;
  font-weight: 600;
  background: color-mix(in srgb, var(--primary) 12%, transparent);
  color: var(--primary);
  white-space: nowrap;
}

.badge-accent {
  background: color-mix(in srgb, var(--accent) 20%, transparent);
  color: color-mix(in srgb, var(--accent) 80%, #000);
}

.badge-secondary {
  background: color-mix(in srgb, var(--secondary) 15%, transparent);
  color: var(--secondary);
}

/* ── Cards (base) ── */
.card {
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.card-base {
  background: var(--bg-card);
  border-radius: var(--radius);
  border: var(--border-width) solid var(--border);
  transition: transform var(--transition), box-shadow var(--transition);
}

/* ── Disabled button state ── */
.btn-disabled {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
}

/* ── Progress Bar ── */
.progress-bar {
  width: 100%;
  height: 6px;
  background: var(--border);
  border-radius: 3px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--secondary), var(--success));
  border-radius: 3px;
  transition: width 0.6s cubic-bezier(0.4,0,0.2,1);
}

/* ────────────────────────────────────────
   HOME – HERO
──────────────────────────────────────── */
.hero {
  padding: 80px 0 60px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 70% 60% at 50% 0%, color-mix(in srgb, var(--primary) 8%, transparent), transparent);
  pointer-events: none;
}

.hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 100px;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  background: color-mix(in srgb, var(--accent) 20%, transparent);
  color: color-mix(in srgb, var(--accent) 80%, #000);
  margin-bottom: 20px;
}

.hero-title {
  font-family: 'Poppins', sans-serif;
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  line-height: 1.15;
  max-width: 800px;
  margin: 0 auto 20px;
}

.hero-title .highlight {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 560px;
  margin: 0 auto 36px;
}

.hero-cta {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 60px;
}

/* Floating math decorations */
.hero-math-floats {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
}

.math-float {
  position: absolute;
  font-size: 1.2rem;
  opacity: 0.07;
  font-family: 'Poppins', sans-serif;
  font-weight: 700;
  color: var(--primary);
  animation: float 6s ease-in-out infinite;
  white-space: nowrap;
}

.math-float:nth-child(1) { top: 10%; left: 5%;  animation-delay: 0s; }
.math-float:nth-child(2) { top: 20%; right: 8%; animation-delay: 1s; }
.math-float:nth-child(3) { top: 55%; left: 3%;  animation-delay: 2s; }
.math-float:nth-child(4) { top: 65%; right: 5%; animation-delay: 0.5s; }
.math-float:nth-child(5) { top: 35%; left: 10%; animation-delay: 1.5s; }
.math-float:nth-child(6) { top: 40%; right: 10%;animation-delay: 2.5s; }

@keyframes float {
  0%, 100% { transform: translateY(0px) rotate(-3deg); }
  50%       { transform: translateY(-12px) rotate(3deg); }
}

/* Hero stats */
.hero-stats {
  display: flex;
  justify-content: center;
  gap: 48px;
  flex-wrap: wrap;
}

.hero-stat {
  text-align: center;
}

.hero-stat-number {
  font-family: 'Poppins', sans-serif;
  font-size: 2rem;
  font-weight: 800;
  color: var(--primary);
  line-height: 1;
}

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

/* ── Features section ── */
.section {
  padding: 64px 0;
}

.section-title {
  font-size: clamp(1.5rem, 3vw, 2rem);
  text-align: center;
  margin-bottom: 8px;
}

.section-subtitle {
  text-align: center;
  color: var(--text-muted);
  margin-bottom: 40px;
}

/* ── Continue section ── */
.continue-section {
  background: color-mix(in srgb, var(--primary) 4%, var(--bg));
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.continue-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-md);
}

.continue-card {
  padding: 20px;
  background: var(--bg-card);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition);
}
.continue-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); }

.continue-card-top {
  display: flex;
  align-items: center;
  gap: 12px;
}
.continue-card-icon { font-size: 1.8rem; }
.continue-card-title { font-family: 'Poppins', sans-serif; font-weight: 600; font-size: 0.95rem; }
.continue-card-level { font-size: 0.8rem; color: var(--text-muted); }

/* ── Stats dashboard ── */
.stats-section {
  padding: 48px 0;
}

.stats-overview {
  display: grid;
  grid-template-columns: 1fr 1.5fr;
  gap: var(--space-lg);
  align-items: start;
}

.stats-global {
  background: var(--bg-card);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  padding: 28px 24px;
  text-align: center;
}
.stats-global-number {
  font-family: 'Poppins', sans-serif;
  font-size: 2.8rem;
  font-weight: 800;
  color: var(--primary);
  line-height: 1;
}
.stats-global-total {
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--text-muted);
}
.stats-global-label {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-top: 6px;
}

.stats-levels {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.stats-level-card {
  padding: var(--space-md) 20px;
}
.stats-level-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
  font-size: 0.9rem;
  font-weight: 600;
}
.stats-level-count {
  color: var(--text-muted);
  font-weight: 500;
}

@media (max-width: 600px) {
  .stats-overview { grid-template-columns: 1fr; }
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
}

.feature-card {
  padding: 28px var(--space-lg);
}

.feature-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }

.feature-icon {
  font-size: 2rem;
  margin-bottom: 14px;
}

.feature-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.feature-desc {
  color: var(--text-muted);
  font-size: 0.9rem;
  line-height: 1.6;
}

/* ────────────────────────────────────────
   LEVELS PAGE
──────────────────────────────────────── */
.page-header {
  padding: 48px 0 32px;
  text-align: center;
}

.page-title {
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
  margin-bottom: 10px;
}

.page-subtitle {
  color: var(--text-muted);
  font-size: 1rem;
}

.levels-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
  padding-bottom: 60px;
}

.level-card {
  padding: 32px 28px;
  border-radius: var(--radius);
  background: var(--bg-card);
  border: 2px solid var(--border);
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.level-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  border-radius: var(--radius) var(--radius) 0 0;
  background: var(--level-color, var(--primary));
}

.level-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
  border-color: var(--level-color, var(--primary));
}

.level-card-icon { font-size: 2.8rem; margin-bottom: 16px; }

.level-card-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.level-card-subtitle {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 16px;
}

.level-card-count {
  display: inline-block;
  padding: 4px 14px;
  border-radius: 100px;
  font-size: 0.8rem;
  font-weight: 600;
  background: color-mix(in srgb, var(--level-color, var(--primary)) 12%, transparent);
  color: var(--level-color, var(--primary));
}

/* ────────────────────────────────────────
   MODULES GRID
──────────────────────────────────────── */

/* ── Level switcher tabs ── */
.level-switcher {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 32px 0 0;
  border-bottom: 2px solid var(--border);
  margin-bottom: 20px;
}

.level-switch-tabs {
  display: flex;
  gap: 4px;
  margin-bottom: -2px;
}

.level-switch-btn {
  padding: 10px 18px;
  font-family: 'Poppins', sans-serif;
  font-weight: 600;
  font-size: 0.88rem;
  border: none;
  border-bottom: 2px solid transparent;
  border-radius: 8px 8px 0 0;
  background: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: color var(--transition), border-color var(--transition), background var(--transition);
  white-space: nowrap;
}

.level-switch-btn:hover {
  color: var(--primary);
  background: color-mix(in srgb, var(--primary) 5%, var(--bg-card));
}

.level-switch-btn.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

/* ── Search bar ── */
.search-bar-wrapper {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--bg-card);
  border: var(--border-width) solid var(--border);
  border-radius: var(--radius);
  padding: 10px 16px;
  margin-bottom: 16px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.search-bar-wrapper:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 12%, transparent);
}

.search-icon { font-size: 1rem; flex-shrink: 0; opacity: 0.45; }

.search-input {
  flex: 1;
  border: none;
  background: none;
  font-size: 0.95rem;
  font-family: 'Inter', sans-serif;
  color: var(--text);
  outline: none;
  min-width: 0;
}

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

.search-clear {
  display: flex;
  align-items: center;
  justify-content: center;
  border: none;
  background: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.9rem;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  flex-shrink: 0;
  transition: background var(--transition), color var(--transition);
}

.search-clear:hover {
  background: color-mix(in srgb, var(--error) 12%, transparent);
  color: var(--error);
}

/* ── Search tools row ── */
.search-tools-row {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--space-md);
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.sort-selector { flex-shrink: 0; }

.sort-select {
  padding: 7px 14px;
  border-radius: 100px;
  border: var(--border-width) solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  font-size: 0.82rem;
  font-family: 'Inter', sans-serif;
  cursor: pointer;
  transition: border-color var(--transition);
}
.sort-select:focus { border-color: var(--primary); }

/* ── Keyword filter tags ── */
.keyword-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  flex: 1;
}

.keyword-tag {
  padding: 5px 14px;
  border-radius: 100px;
  border: var(--border-width) solid var(--border);
  background: var(--bg-card);
  color: var(--text-muted);
  font-size: 0.82rem;
  font-family: 'Inter', sans-serif;
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
}

.keyword-tag:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: color-mix(in srgb, var(--primary) 8%, var(--bg-card));
}

.keyword-tag.active {
  border-color: var(--primary);
  background: var(--primary);
  color: var(--on-primary);
}

/* ── No results ── */
.no-results {
  text-align: center;
  padding: 48px 20px;
  color: var(--text-muted);
  font-size: 1rem;
  line-height: 1.6;
}

/* ── Level card progress ── */
.level-card-progress {
  margin-top: 14px;
}

.level-card-progress-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.level-card-progress-bar {
  height: 5px;
  background: color-mix(in srgb, var(--level-color, var(--primary)) 20%, transparent);
  border-radius: 100px;
  overflow: hidden;
}

.level-card-progress-fill {
  height: 100%;
  background: var(--level-color, var(--primary));
  border-radius: 100px;
  transition: width 0.6s ease;
}

/* ── Module prev/next navigation ── */
.module-nav-arrows {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  padding: 28px 0 40px;
  border-top: 1px solid var(--border);
  margin-top: 32px;
}

.module-nav-counter {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-family: 'Poppins', sans-serif;
  white-space: nowrap;
  flex-shrink: 0;
}

.btn-nav {
  max-width: 42%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  font-size: 0.875rem;
}

.modules-header {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 40px 0 28px;
}

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  border: 1px solid var(--border);
  background: var(--bg-card);
  transition: color var(--transition), background var(--transition), border-color var(--transition);
}

.btn-back:hover {
  color: var(--primary);
  border-color: var(--primary);
  background: color-mix(in srgb, var(--primary) 5%, var(--bg-card));
}

.modules-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
  padding-bottom: 60px;
}

.module-card {
  padding: var(--space-lg);
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.module-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary);
}

.module-card-top {
  display: flex;
  align-items: flex-start;
  gap: 14px;
}

.module-card-icon {
  font-size: 2rem;
  flex-shrink: 0;
  line-height: 1;
  padding-top: 2px;
}

.module-card-info { flex: 1; min-width: 0; }

.module-card-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 4px;
  line-height: 1.3;
}

.module-card-subtitle {
  color: var(--text-muted);
  font-size: 0.8rem;
}

.module-card-keywords {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.module-card-physics {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-style: italic;
}

.module-card-progress {
  margin-top: 4px;
}

.progress-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-bottom: 4px;
}

/* ────────────────────────────────────────
   MODULE DETAIL (tabs)
──────────────────────────────────────── */
.module-detail {
  padding-bottom: 60px;
}

.module-detail-header {
  padding: 36px 0 0;
}

.module-breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.breadcrumb-sep { opacity: 0.4; }

.breadcrumb-link {
  color: var(--primary);
  cursor: pointer;
  font-weight: 500;
  background: none;
  border: none;
  font-family: inherit;
  font-size: inherit;
  padding: 0;
}
.breadcrumb-link:hover { text-decoration: underline; }

.module-detail-title-row {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: 8px;
  flex-wrap: wrap;
}

.module-detail-icon {
  font-size: 2.5rem;
  line-height: 1;
}

.module-detail-title {
  font-size: clamp(1.4rem, 3vw, 2rem);
  font-family: 'Poppins', sans-serif;
  font-weight: 800;
}

.module-detail-subtitle {
  color: var(--text-muted);
  margin-bottom: 4px;
}

.module-detail-physics {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  color: var(--secondary);
  font-weight: 500;
}

/* ── Tab Bar ── */
.tab-bar {
  display: flex;
  gap: 4px;
  border-bottom: 2px solid var(--border);
  margin: 24px 0 0;
  overflow-x: auto;
  scrollbar-width: none;
}
.tab-bar::-webkit-scrollbar { display: none; }

.tab-btn {
  padding: 12px 20px;
  font-family: 'Poppins', sans-serif;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-muted);
  border: none;
  background: transparent;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  margin-bottom: -2px;
  white-space: nowrap;
  transition: color var(--transition), border-color var(--transition);
}

.tab-btn:hover { color: var(--primary); }

.tab-btn.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

/* ── Tab Content ── */
.tab-content { padding: 32px 0; }

/* ── COURS ── */
.cours-content { max-width: 760px; }

.cours-intro {
  font-size: 1.05rem;
  color: var(--text-muted);
  line-height: 1.7;
  margin-bottom: 28px;
  padding: 20px 24px;
  background: color-mix(in srgb, var(--primary) 5%, var(--bg-card));
  border-left: 4px solid var(--primary);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.cours-section {
  margin-bottom: 32px;
}

.cours-section-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 16px;
  color: var(--primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.cours-steps {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.cours-step {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}

.step-number {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--primary);
  color: var(--on-primary);
  font-family: 'Poppins', sans-serif;
  font-weight: 700;
  font-size: 0.8rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

[data-theme="dark"] .step-number { background: var(--primary); color: var(--bg); }

.step-text {
  flex: 1;
  padding-top: 4px;
  font-size: 0.95rem;
  line-height: 1.6;
}

.formulas-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 8px;
}

.formula-chip {
  padding: 10px 18px;
  background: color-mix(in srgb, var(--primary) 8%, var(--bg-card));
  border: 1px solid color-mix(in srgb, var(--primary) 20%, transparent);
  border-radius: var(--radius);
  font-size: 1rem;
  color: var(--text);
}

.piege-box {
  display: flex;
  gap: 12px;
  padding: 16px 20px;
  background: color-mix(in srgb, var(--error) 8%, transparent);
  border: 1px solid color-mix(in srgb, var(--error) 25%, transparent);
  border-radius: var(--radius);
  font-size: 0.9rem;
  line-height: 1.6;
}

.piege-icon { font-size: 1.2rem; flex-shrink: 0; }

/* ── ERREUR / CONSEIL CARD ── */
.erreur-conseil-card {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
}
.erreur-conseil-card.single { grid-template-columns: 1fr; }
@media (max-width: 600px) {
  .erreur-conseil-card { grid-template-columns: 1fr; }
}
.erreur-panel,
.conseil-panel {
  padding: 18px 20px;
  font-size: 0.9rem;
  line-height: 1.65;
}
.erreur-panel {
  background: color-mix(in srgb, var(--error) 8%, var(--bg-card));
  border-right: 1px solid color-mix(in srgb, var(--error) 20%, transparent);
}
.erreur-conseil-card.single .erreur-panel { border-right: none; }
@media (max-width: 600px) {
  .erreur-panel { border-right: none; border-bottom: 1px solid color-mix(in srgb, var(--error) 20%, transparent); }
}
.conseil-panel { background: color-mix(in srgb, var(--success) 8%, var(--bg-card)); }
.panel-label {
  display: flex;
  align-items: center;
  gap: 6px;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 10px;
}
.erreur-panel .panel-label { color: var(--error); }
.conseil-panel .panel-label { color: var(--success); }
.panel-icon { font-size: 1rem; }
.panel-text { margin: 0; color: var(--text); }

/* ── QUIZ ── */
.quiz-card {
  max-width: 680px;
  margin: 0 auto;
}

.quiz-progress-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}

.quiz-question-text {
  font-family: 'Poppins', sans-serif;
  font-size: 1.15rem;
  font-weight: 600;
  line-height: 1.5;
  margin-bottom: 24px;
  color: var(--text);
}

.quiz-options {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 20px;
}

.quiz-option {
  padding: 14px 18px;
  border-radius: var(--radius);
  border: 2px solid var(--border);
  background: var(--bg-card);
  cursor: pointer;
  transition: border-color var(--transition), background var(--transition), transform var(--transition);
  font-size: 0.95rem;
  text-align: left;
  display: flex;
  align-items: center;
  gap: 12px;
}

.quiz-option-letter {
  flex-shrink: 0;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: var(--bg);
  font-size: 0.75rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Poppins', sans-serif;
}

.quiz-option:hover:not([disabled]) {
  border-color: var(--primary);
  background: color-mix(in srgb, var(--primary) 5%, var(--bg-card));
  transform: translateX(4px);
}

.quiz-option.correct {
  border-color: var(--success);
  background: color-mix(in srgb, var(--success) 10%, var(--bg-card));
}
.quiz-option.correct .quiz-option-letter {
  background: var(--success);
  border-color: var(--success);
  color: var(--on-success);
}

.quiz-option.wrong {
  border-color: var(--error);
  background: color-mix(in srgb, var(--error) 10%, var(--bg-card));
}
.quiz-option.wrong .quiz-option-letter {
  background: var(--error);
  border-color: var(--error);
  color: var(--on-error);
}

.quiz-option[disabled] { cursor: not-allowed; }

.quiz-correction {
  padding: 14px 18px;
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--secondary) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--secondary) 30%, transparent);
  font-size: 0.9rem;
  line-height: 1.6;
  animation: slide-down var(--transition);
  margin-bottom: 16px;
}

.quiz-nav { display: flex; justify-content: flex-end; }

/* Quiz results */
.quiz-results {
  text-align: center;
  padding: 40px 24px;
}

.score-display {
  font-family: 'Poppins', sans-serif;
  font-size: 5rem;
  font-weight: 800;
  color: var(--primary);
  line-height: 1;
  margin-bottom: 8px;
}

.score-fraction {
  font-size: 1.1rem;
  color: var(--text-muted);
  margin-bottom: 24px;
}

.score-message {
  font-size: 1.1rem;
  color: var(--text);
  margin-bottom: 32px;
  max-width: 400px;
  margin-left: auto;
  margin-right: auto;
}

/* ── EXERCICE ── */
.card-exercise {
  max-width: 700px;
  margin: 0 auto;
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 2px solid var(--border);
  padding: 32px;
  transition: border-color 0.3s, box-shadow 0.3s;
  position: relative;
}

.card-exercise.state-error {
  border-color: var(--error);
  animation: shake 0.5s ease;
}

.card-exercise.state-success {
  border-color: var(--success);
  animation: glow-success 1s ease;
}

.exercice-statement {
  font-size: 1.05rem;
  line-height: 1.7;
  margin-bottom: 28px;
}

.exercice-input-row {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.exercice-input {
  flex: 1;
  min-width: 120px;
  max-width: 200px;
  padding: 12px 16px;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  font-family: 'Inter', sans-serif;
  font-size: 1rem;
  background: var(--bg);
  color: var(--text);
  transition: border-color var(--transition);
  outline: none;
}
.exercice-input:focus { border-color: var(--primary); }

.exercice-unit {
  font-size: 0.9rem;
  color: var(--text-muted);
  font-weight: 500;
}

.exercice-feedback {
  margin-top: 12px;
  padding: 12px 16px;
  border-radius: var(--radius);
  font-size: 0.9rem;
  line-height: 1.6;
  animation: slide-down 0.25s ease;
}

.feedback-error {
  background: color-mix(in srgb, var(--error) 10%, transparent);
  border: 1px solid color-mix(in srgb, var(--error) 30%, transparent);
  color: var(--text);
}

.feedback-success {
  background: color-mix(in srgb, var(--success) 10%, transparent);
  border: 1px solid color-mix(in srgb, var(--success) 30%, transparent);
  color: var(--text);
}

.hint-box {
  margin-top: 16px;
  padding: 16px 20px;
  background: color-mix(in srgb, var(--secondary) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--secondary) 30%, transparent);
  border-radius: var(--radius);
  font-size: 0.9rem;
  line-height: 1.6;
  animation: slide-down 0.3s ease;
}

.hint-box-title {
  font-weight: 600;
  color: var(--secondary);
  margin-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.solution-reveal {
  margin-top: 16px;
  animation: slide-down 0.3s ease;
}

.step-solution {
  display: flex;
  gap: 14px;
  align-items: flex-start;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
  line-height: 1.6;
}

.step-solution:last-child { border-bottom: none; }

.step-solution-num {
  flex-shrink: 0;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: color-mix(in srgb, var(--primary) 15%, transparent);
  color: var(--primary);
  font-weight: 700;
  font-size: 0.75rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.exercice-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 20px;
}

/* ── PROBLEME ── */
.probleme-content { max-width: 760px; }

.probleme-context {
  padding: 20px 24px;
  background: color-mix(in srgb, var(--accent) 8%, var(--bg-card));
  border: 1px solid color-mix(in srgb, var(--accent) 25%, transparent);
  border-radius: var(--radius);
  font-size: 0.95rem;
  line-height: 1.7;
  margin-bottom: 24px;
}

.probleme-context-label {
  font-weight: 700;
  color: color-mix(in srgb, var(--accent) 70%, #000);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 8px;
}

.probleme-tasks {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  margin-bottom: 28px;
}

.task-item {
  padding: 16px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.task-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.task-label {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 4px;
}

.task-text {
  font-size: 0.95rem;
  line-height: 1.6;
}

.task-solution {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--text);
  animation: slide-down 0.3s ease;
}

.task-solution-label {
  font-weight: 700;
  color: var(--success);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 6px;
}

.final-answer-box {
  padding: 16px 20px;
  background: color-mix(in srgb, var(--success) 10%, transparent);
  border: 2px solid var(--success);
  border-radius: var(--radius);
  font-weight: 600;
  text-align: center;
  animation: glow-success 1.5s ease;
}

.module-complete-banner {
  text-align: center;
  padding: 32px;
  background: linear-gradient(135deg, color-mix(in srgb, var(--success) 10%, var(--bg-card)), color-mix(in srgb, var(--secondary) 10%, var(--bg-card)));
  border-radius: var(--radius);
  border: 1px solid var(--border);
  margin-top: 24px;
  animation: slide-down 0.5s ease;
}

.module-complete-icon { font-size: 3rem; margin-bottom: 12px; }
.module-complete-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--success);
}

/* ────────────────────────────────────────
   EVALUATION
──────────────────────────────────────── */
.eval-content { max-width: 760px; }

.eval-header { margin-bottom: 24px; }

.eval-title-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

.eval-badge {
  font-family: 'Poppins', sans-serif;
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
}

.eval-duration {
  font-size: 0.85rem;
  color: var(--text-muted);
  padding: 4px 12px;
  background: color-mix(in srgb, var(--primary) 8%, transparent);
  border-radius: 20px;
}

.eval-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 2px solid var(--border);
  padding: 32px;
  transition: border-color 0.3s, box-shadow 0.3s;
}

.eval-progress-row {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.eval-statement {
  font-size: 1.05rem;
  line-height: 1.7;
  margin-bottom: 28px;
}

.eval-placeholder {
  text-align: center;
  padding: 60px 20px;
}

.eval-results {
  text-align: center;
  animation: slide-down 0.3s ease;
}

.eval-corrections {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  margin-top: 8px;
  text-align: left;
}

.eval-correction-item {
  padding: 16px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  border-left: 4px solid var(--border);
}

.eval-correction-item.correct { border-left-color: var(--success); }
.eval-correction-item.incorrect { border-left-color: var(--error); }

.eval-correction-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 8px;
}

.eval-q-num {
  font-weight: 700;
  font-size: 0.8rem;
  color: var(--primary);
  text-transform: uppercase;
}

.eval-q-points {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-left: auto;
}

.eval-q-statement {
  font-size: 0.92rem;
  line-height: 1.6;
  margin-bottom: 8px;
}

.eval-q-correction {
  font-size: 0.88rem;
  line-height: 1.6;
  color: var(--text-muted);
  padding-top: 8px;
  border-top: 1px solid var(--border);
}

/* ────────────────────────────────────────
   FOOTER
──────────────────────────────────────── */
.footer {
  padding: 28px 0;
  border-top: 1px solid var(--border);
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
  background: var(--bg-card);
  transition: background var(--transition), border-color var(--transition);
}

/* ────────────────────────────────────────
   ANIMATIONS
──────────────────────────────────────── */
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%       { transform: translateX(-8px); }
  40%       { transform: translateX(8px); }
  60%       { transform: translateX(-5px); }
  80%       { transform: translateX(5px); }
}

@keyframes glow-success {
  0%, 100% { box-shadow: 0 0 0 0 rgba(46, 204, 113, 0.4); }
  50%       { box-shadow: 0 0 0 14px rgba(46, 204, 113, 0); }
}

@keyframes slide-down {
  from { opacity: 0; transform: translateY(-10px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes confetti-fall {
  0%   { transform: translateY(-20px) rotate(0deg); opacity: 1; }
  100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
}

@keyframes fade-in {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes tab-fade-in {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ── Confetti ── */
.confetti-container {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: var(--z-confetti);
  overflow: hidden;
}

.confetti-piece {
  position: absolute;
  top: -20px;
  width: 10px;
  height: 10px;
  border-radius: 2px;
  animation: confetti-fall 3s ease-in forwards;
}

/* ────────────────────────────────────────
   KATEX OVERRIDES
──────────────────────────────────────── */
.katex { font-size: 1.05em; }
.katex-display { margin: 16px 0; }

/* ────────────────────────────────────────
   UTILITIES
──────────────────────────────────────── */
.text-center   { text-align: center; }
.text-muted    { color: var(--text-muted); }
.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; }
.gap-8 { gap: 8px; }

.flex       { display: flex; }
.flex-wrap  { flex-wrap: wrap; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.justify-center  { justify-content: center; }

.divider {
  height: 1px;
  background: var(--border);
  margin: 32px 0;
}

/* ── Toast notifications ── */
.toast {
  position: fixed;
  bottom: 28px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  z-index: var(--z-toast);
  padding: 14px 28px;
  border-radius: var(--radius);
  font-family: 'Inter', sans-serif;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--on-success);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transition: opacity 0.3s ease, transform 0.3s ease;
  cursor: pointer;
  max-width: 90vw;
  text-align: center;
}
.toast-visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}
.toast-exit {
  opacity: 0;
  transform: translateX(-50%) translateY(20px);
}
.toast-success {
  background: var(--success);
}
.toast-achievement {
  background: linear-gradient(135deg, #F4D03F 0%, #D4AC0D 100%);
  color: #2C3E50;
}

/* ── Scroll to top button ── */
.scroll-top-btn {
  position: fixed;
  bottom: 28px;
  right: 28px;
  z-index: var(--z-scroll-top);
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: none;
  background: var(--primary);
  color: var(--on-primary);
  font-size: 1.3rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: var(--shadow);
  backdrop-filter: blur(8px);
  opacity: 0;
  transform: translateY(16px);
  pointer-events: none;
  transition: opacity 0.25s ease, transform 0.25s ease, background 0.2s ease;
}
.scroll-top-btn.visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}
.scroll-top-btn:hover {
  background: var(--secondary);
  transform: translateY(-2px);
}
[data-theme="dark"] .scroll-top-btn {
  background: var(--bg-card);
  color: var(--primary);
  border: 1px solid var(--border);
}
[data-theme="dark"] .scroll-top-btn:hover {
  background: var(--border);
}

/* ── Contact button & panel ── */
.contact-btn {
  position: fixed;
  bottom: 28px;
  left: 28px;
  z-index: var(--z-toast);
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: none;
  background: var(--secondary);
  color: var(--on-primary);
  font-size: 1.4rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: var(--shadow);
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition);
}
.contact-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  background: var(--primary);
}
.contact-btn.active {
  transform: rotate(45deg);
  background: var(--error);
}
[data-theme="dark"] .contact-btn {
  background: var(--bg-card);
  color: var(--secondary);
  border: 1px solid var(--border);
}
[data-theme="dark"] .contact-btn:hover {
  background: var(--border);
}
[data-theme="dark"] .contact-btn.active {
  background: var(--error);
  color: var(--on-error);
  border-color: var(--error);
}

/* Panel */
.contact-panel {
  position: fixed;
  bottom: 88px;
  left: 28px;
  z-index: var(--z-toast);
  width: 340px;
  max-width: calc(100vw - 56px);
  background: var(--bg-card);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transform: translateY(12px) scale(0.95);
  pointer-events: none;
  transition: opacity 0.2s ease, transform 0.2s ease;
}
.contact-panel.open {
  opacity: 1;
  transform: translateY(0) scale(1);
  pointer-events: auto;
}

.contact-panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 20px 12px;
  border-bottom: 1px solid var(--border);
}
.contact-panel-title {
  font-family: 'Poppins', sans-serif;
  font-weight: 700;
  font-size: 1rem;
}
.contact-panel-close {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  color: var(--text-muted);
  line-height: 1;
  padding: 0 4px;
}
.contact-panel-close:hover { color: var(--text); }

.contact-form {
  padding: 16px 20px 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.contact-categories {
  border: none;
  padding: 0;
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}
.contact-cat input { position: absolute; opacity: 0; pointer-events: none; }
.contact-cat-chip {
  display: inline-block;
  padding: 6px 14px;
  border-radius: 20px;
  border: 1px solid var(--border);
  background: var(--bg);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition);
}
.contact-cat input:checked + .contact-cat-chip {
  background: var(--primary);
  color: var(--on-primary);
  border-color: var(--primary);
}
.contact-cat input:focus-visible + .contact-cat-chip {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.contact-message {
  width: 100%;
  min-height: 90px;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', sans-serif;
  font-size: 0.9rem;
  resize: vertical;
  transition: border-color var(--transition);
}
.contact-message:focus {
  outline: none;
  border-color: var(--primary);
}

.contact-send {
  align-self: flex-end;
  padding: 10px 24px;
  font-size: 0.88rem;
}

.contact-success {
  text-align: center;
  padding: 24px 20px;
  font-size: 0.95rem;
  color: var(--text);
  line-height: 1.6;
}

/* ── Page & tab transitions ── */
#app > * { animation: fade-in 0.2s ease-out; }
.tab-content { animation: tab-fade-in 0.2s ease-out; }

/* ────────────────────────────────────────
   RESPONSIVE
──────────────────────────────────────── */

/* ── KaTeX overflow protection (all sizes) ── */
.katex-display { overflow-x: auto; overflow-y: hidden; }

/* ── Large tablet / small desktop (≤ 1024px) ── */
@media (max-width: 1024px) {
  .container { max-width: 900px; }
  .hero-stats { gap: 36px; }
  .stats-overview { grid-template-columns: 1fr 1.5fr; gap: var(--space-md); }
}

/* ── Tablet (≤ 768px) ── */
@media (max-width: 768px) {
  .container { max-width: 100%; }

  /* Header */
  .header-inner { gap: var(--space-sm); }
  .nav-link { padding: 8px 12px; font-size: 0.9rem; }

  /* Hero */
  .hero { padding: 60px 0 48px; }
  .hero-subtitle { font-size: 1.05rem; }
  .hero-stats { gap: 32px; }
  .hero-math-floats { display: none; }

  /* Sections */
  .section { padding: 48px 0; }
  .page-header { padding: 36px 0 24px; }

  /* Grids */
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .modules-grid  { grid-template-columns: repeat(2, 1fr); }
  .levels-grid   { grid-template-columns: repeat(2, 1fr); gap: var(--space-md); }

  /* Stats */
  .stats-overview { grid-template-columns: 1fr; }

  /* Tab bar — horizontal scroll */
  .tab-bar {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    gap: 4px;
    padding-bottom: 4px;
  }
  .tab-bar::-webkit-scrollbar { display: none; }

  /* Touch targets — minimum 44px */
  .tab-btn { white-space: nowrap; min-height: 44px; }
  .btn { min-height: 44px; }
  .quiz-option { min-height: 44px; }
  .keyword-tag { min-height: 36px; }
  .level-switch-btn { min-height: 44px; }
  .nav-link { min-height: 44px; display: inline-flex; align-items: center; }
  .theme-toggle { min-width: 44px; min-height: 44px; }
  .search-clear { min-width: 36px; min-height: 36px; }

  /* Level switcher — horizontal scroll */
  .level-switcher {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
  }
  .level-switcher::-webkit-scrollbar { display: none; }
  .level-switch-tabs { flex-shrink: 0; }

  /* Search tools */
  .search-tools-row { flex-direction: column; gap: var(--space-sm); }
  .sort-selector { align-self: flex-end; }

  /* Cours */
  .cours-content { max-width: 100%; }
  .cours-intro { padding: 16px 18px; font-size: 1rem; }

  /* Exercise / Evaluation */
  .card-exercise { padding: 24px 20px; }
  .eval-card { padding: 24px 20px; }
  .quiz-card { max-width: 100%; }
  .eval-content { max-width: 100%; }
  .probleme-content { max-width: 100%; }

  /* Module nav */
  .module-nav-arrows { flex-wrap: wrap; justify-content: center; }

  /* Contact panel */
  .contact-panel { width: 320px; }
}

/* ── Mobile (≤ 600px) ── */
@media (max-width: 600px) {
  /* Header — compact */
  .header { height: 56px; }
  .header-inner { height: 56px; }
  .logo-text { font-size: 1.05rem; }
  .logo-img { height: 28px; }
  .nav { gap: 2px; }
  .nav-link { padding: 6px 10px; font-size: 0.85rem; }

  /* Hero */
  .hero { padding: 40px 0 32px; }
  .hero-kicker { font-size: 0.72rem; padding: 5px 12px; margin-bottom: 14px; }
  .hero-subtitle { font-size: 0.95rem; margin-bottom: 24px; }
  .hero-cta { flex-direction: column; align-items: center; gap: 10px; margin-bottom: 40px; }
  .hero-cta .btn { width: 100%; max-width: 280px; justify-content: center; }
  .hero-stats { gap: 20px; }
  .hero-stat-number { font-size: 1.6rem; }
  .hero-stat-label { font-size: 0.78rem; }

  /* Sections */
  .section { padding: 36px 0; }
  .section-title { font-size: 1.3rem; }
  .section-subtitle { font-size: 0.9rem; margin-bottom: 28px; }
  .page-header { padding: 28px 0 20px; }
  .page-title { font-size: 1.5rem; }

  /* Grids — single column */
  .features-grid { grid-template-columns: 1fr; gap: var(--space-md); }
  .levels-grid { grid-template-columns: 1fr; }
  .modules-grid { grid-template-columns: 1fr; }
  .continue-grid { grid-template-columns: 1fr; }

  /* Feature cards */
  .feature-card { padding: 20px var(--space-md); }

  /* Level cards */
  .level-card { padding: 24px 20px; }
  .level-card-icon { font-size: 2.2rem; margin-bottom: 12px; }
  .level-card-title { font-size: 1.15rem; }

  /* Module cards */
  .module-card { padding: var(--space-md); }
  .module-card-icon { font-size: 1.6rem; }
  .module-card-title { font-size: 0.95rem; }

  /* Level switcher */
  .level-switcher { flex-wrap: nowrap; gap: 4px; padding-top: 20px; }
  .level-switch-btn { padding: 8px 12px; font-size: 0.8rem; }

  /* Search bar */
  .search-bar-wrapper { padding: 8px 12px; }
  .search-input { font-size: 0.9rem; }

  /* Keywords */
  .keyword-tag { padding: 4px 10px; font-size: 0.78rem; }

  /* Module detail */
  .module-detail-header { padding: 24px 0 0; }
  .module-detail-icon { font-size: 2rem; }
  .module-detail-title-row { gap: 10px; }
  .module-breadcrumb { font-size: 0.8rem; gap: 6px; }

  /* Tabs */
  .tab-bar { margin: 16px 0 0; }
  .tab-btn { padding: 10px 14px; font-size: 0.82rem; }
  .tab-content { padding: 24px 0; }

  /* Cours */
  .cours-intro { padding: 14px 16px; font-size: 0.95rem; }
  .cours-section-title { font-size: 1rem; }
  .cours-step { gap: 10px; }
  .step-text { font-size: 0.9rem; }
  .formulas-grid { gap: 8px; }
  .formula-chip { padding: 8px 14px; font-size: 0.92rem; }
  .piege-box { padding: 14px 16px; font-size: 0.85rem; }

  /* Quiz */
  .quiz-question-text { font-size: 1.05rem; margin-bottom: 18px; }
  .quiz-option { padding: 12px 14px; font-size: 0.9rem; gap: 10px; }
  .quiz-correction { padding: 12px 14px; font-size: 0.85rem; }
  .score-display { font-size: 3.5rem; }
  .score-message { font-size: 1rem; }

  /* Exercise */
  .card-exercise { padding: 20px 16px; }
  .exercice-statement { font-size: 1rem; margin-bottom: 20px; }
  .exercice-input-row { flex-direction: column; align-items: stretch; }
  .exercice-input { max-width: 100%; }
  .exercice-actions { flex-direction: column; }
  .exercice-actions .btn { width: 100%; justify-content: center; }

  /* Problème */
  .probleme-context { padding: 16px 18px; font-size: 0.9rem; }
  .task-item { padding: 14px 16px; }
  .task-header { gap: 8px; }

  /* Evaluation */
  .eval-card { padding: 20px 16px; }
  .eval-title-row { flex-direction: column; align-items: flex-start; gap: 8px; }
  .eval-statement { font-size: 1rem; margin-bottom: 20px; }
  .eval-correction-item { padding: 14px 16px; }

  /* Erreur / Conseil */
  .erreur-conseil-card { grid-template-columns: 1fr; }
  .erreur-panel { border-right: none; border-bottom: 1px solid color-mix(in srgb, var(--error) 20%, transparent); }

  /* Module navigation */
  .module-nav-arrows { gap: 8px; }
  .btn-nav { max-width: 38%; font-size: 0.8rem; padding: 8px 12px; }
  .module-nav-counter { font-size: 0.75rem; }

  /* Buttons */
  .btn { padding: 10px 18px; font-size: 0.9rem; }
  .btn-back { padding: 6px 12px; font-size: 0.82rem; }
  .modules-header { padding: 28px 0 20px; gap: 10px; }

  /* Stats */
  .stats-global-number { font-size: 2.2rem; }
  .stats-global { padding: 20px 16px; }

  /* Footer */
  .footer { padding: 20px 0; font-size: 0.8rem; }

  /* Fixed buttons — smaller on mobile */
  .scroll-top-btn { width: 42px; height: 42px; font-size: 1.1rem; right: 16px; bottom: 20px; }
  .contact-btn { width: 42px; height: 42px; font-size: 1.2rem; left: 16px; bottom: 20px; }
  .contact-panel { left: 12px; bottom: 72px; width: calc(100vw - 24px); max-width: calc(100vw - 24px); }

  /* Toast */
  .toast { bottom: 72px; padding: 12px 20px; font-size: 0.85rem; }
}

/* ── Small mobile (≤ 400px) ── */
@media (max-width: 400px) {
  .container { padding: 0 12px; }
  .hero-title { font-size: 1.5rem; }
  .hero-subtitle { font-size: 0.88rem; }

  /* Hide logo text on very small screens */
  .logo-learning { display: none; }
  .logo-text { font-size: 1.1rem; }

  /* Even more compact UI */
  .level-card { padding: 20px 16px; }
  .module-card { padding: 14px; }
  .module-card-top { gap: 10px; }
  .module-card-icon { font-size: 1.4rem; }

  /* Tabs scroll gracefully */
  .tab-btn { padding: 8px 10px; font-size: 0.78rem; }

  /* Quiz / Exercise */
  .quiz-option { padding: 10px 12px; }
  .card-exercise { padding: 16px 12px; }
  .eval-card { padding: 16px 12px; }

  /* Score */
  .score-display { font-size: 2.8rem; }

  /* Contact */
  .contact-panel { left: 8px; width: calc(100vw - 16px); max-width: calc(100vw - 16px); }
  .contact-form { padding: 12px 14px 16px; }
  .contact-cat-chip { font-size: 0.75rem; padding: 5px 10px; }
}

/* ── Landscape phones ── */
@media (max-height: 500px) and (orientation: landscape) {
  .hero { padding: 24px 0 20px; }
  .hero-cta { margin-bottom: 20px; }
  .hero-stats { gap: 24px; }
  .hero-math-floats { display: none; }
  .section { padding: 28px 0; }
}

/* ── Hover only on devices that support it ── */
@media (hover: none) {
  .module-card:hover { transform: none; box-shadow: var(--shadow); }
  .level-card:hover { transform: none; box-shadow: var(--shadow); }
  .feature-card:hover { transform: none; }
  .continue-card:hover { transform: none; }
  .btn:hover { transform: none; }
  .quiz-option:hover:not([disabled]) { transform: none; }
  .theme-toggle:hover { transform: none; }

  /* Active states for touch feedback */
  .module-card:active { transform: scale(0.98); }
  .level-card:active { transform: scale(0.98); }
  .btn:active { transform: scale(0.97); }
  .quiz-option:active:not([disabled]) { transform: scale(0.98); }
}

/* ── Print styles ── */
@media print {
  .header, .footer, .scroll-top-btn, .contact-btn, .contact-panel, .hero-math-floats { display: none; }
  .hero { padding: 20px 0; }
  body { background: #fff; color: #000; }
}