@charset "UTF-8";
/**
 * Full Skin — 008-math
 * Primary:  #4f46e5 (indigo)   Accent: #22c55e (fresh green)
 * Hero:     Clean white + premium indigo gradient
 * Feel:     Khan Academy × Apple — authoritative, bright, premium math
 */

/* ═══ Font Import ═══ */
@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&display=swap');

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

/* ═══ Base Overrides ═══ */
html { scroll-behavior: smooth; }

::selection { background: var(--site-primary-light, #eef2ff); color: var(--site-primary-dark, #312e81); }
::-moz-selection { background: var(--site-primary-light, #eef2ff); color: var(--site-primary-dark, #312e81); }

*:focus-visible {
  outline: 3px solid var(--site-primary, #4f46e5);
  outline-offset: 2px;
  border-radius: var(--radius-sm, 6px);
}

/* ═══ Scrollbar ═══ */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--site-primary-light, #eef2ff); }
::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--site-primary, #4f46e5) 0%, var(--site-primary-hover, #4338ca) 100%);
  border-radius: 5px;
  border: 2px solid var(--site-primary-light, #eef2ff);
}
::-webkit-scrollbar-thumb:hover {
  background: linear-gradient(180deg, var(--site-primary-hover, #4338ca) 0%, var(--site-primary-dark, #312e81) 100%);
}
html { scrollbar-color: var(--site-primary, #4f46e5) var(--site-primary-light, #eef2ff); }

/* ═══ Body Background ═══ */
body {
  background: linear-gradient(160deg, #eef2ff 0%, #ffffff 50%, #f0fdf4 100%);
  background-attachment: fixed;
  color: var(--site-text, #111827);
  font-family: var(--font-body);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ═══ Typography ═══ */
.page-header h1 {
  font-family: var(--font-heading);
  font-size: var(--text-3xl, 2rem);
  font-weight: 800;
  color: var(--site-primary-dark, #312e81);
  line-height: 1.2;
  letter-spacing: -0.03em;
}

.page-header .subtitle {
  color: var(--site-text-light, #4b5563);
  font-size: 1.05rem;
  margin-top: 0.4rem;
}

/* ═══ Hero ═══ */
.page-header {
  background: #ffffff;
  border-bottom: 1px solid var(--site-primary-border, #c7d2fe);
  padding: 1.5rem 1.5rem 1rem;
}

.hero {
  background: linear-gradient(160deg, #eef2ff 0%, #ffffff 60%, #f0fdf4 100%);
  border-bottom: 2px solid var(--site-primary-border, #c7d2fe);
  padding: 4rem 2rem 3rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}

/* Hero decorative orbs */
.hero::before {
  content: '';
  position: absolute;
  top: -60px; right: -60px;
  width: 280px; height: 280px;
  background: radial-gradient(circle, rgba(79, 70, 229, 0.10) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
  z-index: 0;
}
.hero::after {
  content: '';
  position: absolute;
  bottom: -40px; left: -50px;
  width: 200px; height: 200px;
  background: radial-gradient(circle, rgba(34, 197, 94, 0.09) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
  z-index: 0;
}

.hero h1 {
  font-family: var(--font-heading);
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  font-weight: 800;
  color: var(--site-primary-dark, #312e81);
  letter-spacing: -0.035em;
  line-height: 1.15;
  position: relative;
  z-index: 1;
}

.hero .subtitle {
  font-size: 1.125rem;
  color: var(--site-text-light, #4b5563);
  margin-top: 0.875rem;
  max-width: 560px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.6;
  position: relative;
  z-index: 1;
}

/* Hero stats */
.hero-stats {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  margin-top: 2rem;
  flex-wrap: wrap;
  position: relative;
  z-index: 1;
}

.stat-item {
  text-align: center;
  padding: 1rem 1.5rem;
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-lg, 14px);
  box-shadow: var(--shadow-sm);
  transition: transform var(--dur-normal) var(--ease-default),
              box-shadow var(--dur-normal) var(--ease-default),
              border-color var(--dur-normal) var(--ease-default);
  min-width: 120px;
}

.stat-item:hover {
  transform: translateY(-3px);
  border-color: var(--site-primary, #4f46e5);
  box-shadow: var(--shadow-md);
}

.stat-number {
  display: block;
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--site-primary, #4f46e5);
  font-variant-numeric: tabular-nums lining-nums;
  font-feature-settings: "tnum" 1, "lnum" 1;
  letter-spacing: -0.02em;
}

.stat-label {
  display: block;
  font-size: var(--text-xs, 0.75rem);
  font-weight: 600;
  color: var(--site-text-muted, #6b7280);
  margin-top: 0.2rem;
  text-transform: uppercase;
  letter-spacing: 0.07em;
}

/* ═══ Grade Badge Indicators ═══ */
.grade-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem 0.75rem;
  border-radius: var(--radius-pill);
  font-size: var(--text-xs, 0.75rem);
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  font-family: var(--font-heading);
}

.grade-badge--k   { background: #fef9c3; color: #854d0e; border: 1px solid #fde047; }
.grade-badge--g1  { background: #fee2e2; color: #991b1b; border: 1px solid #fca5a5; }
.grade-badge--g2  { background: #ffedd5; color: #9a3412; border: 1px solid #fdba74; }
.grade-badge--g3  { background: var(--site-primary-light, #eef2ff); color: var(--site-primary-dark, #312e81); border: 1px solid var(--site-primary-border, #c7d2fe); }
.grade-badge--g4  { background: #f0fdf4; color: #166534; border: 1px solid #bbf7d0; }
.grade-badge--g5  { background: #fdf4ff; color: #7e22ce; border: 1px solid #e9d5ff; }

/* ═══ Breadcrumb ═══ */
.breadcrumb {
  padding: 0.6rem 1rem;
  margin-bottom: 1rem;
}

.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem;
  list-style: none;
  padding: 0;
  margin: 0;
  font-size: var(--text-sm, 0.875rem);
  color: var(--site-text-muted, #6b7280);
}

.breadcrumb a {
  color: var(--site-primary, #4f46e5);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease-default);
}

.breadcrumb a:hover {
  color: var(--site-primary-hover, #4338ca);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.breadcrumb li:not(:last-child)::after {
  content: '›';
  color: var(--site-border-dark, #d1d5db);
  font-weight: 600;
  margin-left: 0.3rem;
}

.breadcrumb li:last-child {
  color: var(--site-text, #111827);
  font-weight: 600;
}

/* ═══ Set Switcher ═══ */
.set-switcher {
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-xl, 20px);
  box-shadow: var(--shadow-sm);
}

.set-switcher-label {
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 700;
  color: var(--site-text, #111827);
}

.set-btn {
  background: #ffffff;
  border: 2px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-md, 10px);
  color: var(--site-text, #111827);
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: background var(--dur-fast) var(--ease-default),
              border-color var(--dur-fast) var(--ease-default),
              color var(--dur-fast) var(--ease-default),
              box-shadow var(--dur-fast) var(--ease-default);
}

.set-btn:hover {
  border-color: var(--site-primary, #4f46e5);
  background: var(--site-primary-light, #eef2ff);
  box-shadow: var(--shadow-sm);
}

.set-btn.active {
  background: linear-gradient(135deg, var(--site-primary, #4f46e5) 0%, var(--site-primary-hover, #4338ca) 100%);
  color: #ffffff;
  border-color: var(--site-primary-hover, #4338ca);
  box-shadow: var(--shadow-brand);
}

/* ═══ Buttons ═══ */
.btn {
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  border: 2px solid transparent;
  border-radius: var(--radius-button, 12px);
  background: #ffffff;
  color: var(--site-text, #111827);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--dur-fast) var(--ease-default),
              transform var(--dur-fast) var(--ease-default),
              background var(--dur-fast) var(--ease-default),
              border-color var(--dur-fast) var(--ease-default);
  -webkit-font-smoothing: antialiased;
}

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

.btn:active {
  transform: translateY(0) scale(0.97);
  box-shadow: var(--shadow-sm);
  transition-duration: 80ms;
}

.btn-primary {
  background: linear-gradient(135deg, var(--site-primary, #4f46e5) 0%, var(--site-primary-hover, #4338ca) 100%);
  color: #ffffff;
  border-color: var(--site-primary-hover, #4338ca);
  min-height: 44px;
}

.btn-primary:hover {
  background: linear-gradient(135deg, var(--site-primary-hover, #4338ca) 0%, var(--site-primary-dark, #312e81) 100%);
  box-shadow: var(--shadow-brand);
}

.btn-primary:active {
  background: var(--site-primary-dark, #312e81);
  box-shadow: var(--shadow-md);
}

.btn-success,
.btn-answers {
  background: linear-gradient(135deg, var(--site-accent, #22c55e) 0%, var(--site-accent-hover, #16a34a) 100%);
  color: #ffffff;
  border-color: var(--site-accent-hover, #16a34a);
  min-height: 44px;
}

.btn-success:hover,
.btn-answers:hover {
  background: linear-gradient(135deg, var(--site-accent-hover, #16a34a) 0%, var(--site-accent-dark, #15803d) 100%);
  box-shadow: var(--shadow-green);
}

.btn-check {
  background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
  color: #ffffff;
  border-color: #d97706;
  min-height: 44px;
}

.btn-check:hover {
  background: linear-gradient(135deg, #d97706 0%, #b45309 100%);
  box-shadow: 0 6px 20px rgba(245, 158, 11, 0.30);
}

.btn:focus-visible {
  outline: 3px solid var(--site-primary, #4f46e5);
  outline-offset: 3px;
}

.btn.loading {
  pointer-events: none;
  opacity: 0.7;
}

.btn-outline {
  display: inline-block;
  padding: 0.5rem 1rem;
  border: 1.5px solid var(--site-primary, #4f46e5);
  border-radius: var(--radius-button, 12px);
  color: var(--site-primary, #4f46e5);
  background: transparent;
  text-decoration: none;
  font-size: var(--text-sm, 0.875rem);
  font-weight: 600;
  transition: background var(--dur-normal) var(--ease-default),
              color var(--dur-normal) var(--ease-default);
}

.btn-outline:hover {
  background: var(--site-primary, #4f46e5);
  color: #ffffff;
}

.nav-links-group {
  display: flex;
  gap: 0.75rem;
  align-items: center;
  flex-wrap: wrap;
}

/* ═══ Intro Section ═══ */
.intro,
.intro-section {
  background: linear-gradient(135deg, var(--site-primary-light, #eef2ff) 0%, #e0e7ff 100%);
  border: 1px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-card, 14px);
  padding: 1.25rem 1.5rem;
  margin: 1rem 0;
}

.intro h3,
.intro-section h3 {
  font-family: var(--font-heading);
  font-weight: 700;
  color: var(--site-primary-dark, #312e81);
}

.intro p,
.intro-section p { color: var(--site-text-light, #4b5563); line-height: 1.7; }
.intro strong,
.intro-section strong { color: var(--site-primary-dark, #312e81); }

/* ═══ Body Content / Worksheet ═══ */
.body-content {
  background: #ffffff;
  border-radius: 0 0 var(--radius-card, 14px) var(--radius-card, 14px);
  border: 1px solid var(--site-primary-border, #c7d2fe);
  border-top: none;
}

.body-content h2 {
  font-family: var(--font-heading);
  color: var(--site-primary-dark, #312e81);
  font-size: var(--text-2xl, 1.5rem);
  font-weight: 700;
  border-bottom: 2px solid var(--site-primary-light, #eef2ff);
}

.body-content p  { color: var(--site-text, #111827); }
.body-content ul,
.body-content ol { color: var(--site-text, #111827); }
.body-content li strong { color: var(--site-primary, #4f46e5); font-weight: 600; }
.body-content ul li::marker { color: var(--site-primary, #4f46e5); }

.problems-grid { border-top: 2px solid var(--site-primary-border, #c7d2fe); }

.problem {
  background: #ffffff;
  border-bottom: 1px solid var(--site-border, #e5e7eb);
  border-left: 5px solid var(--site-primary, #4f46e5);
  font-size: var(--text-lg, 1.125rem);
  color: var(--site-text, #111827);
  transition: transform var(--dur-fast) var(--ease-default),
              box-shadow var(--dur-fast) var(--ease-default);
}

.problem:hover { transform: translateX(2px); }

/* Problem number badge */
.problem .num {
  background: var(--site-primary-light, #eef2ff);
  color: var(--site-primary, #4f46e5);
  font-family: var(--font-heading);
  font-weight: 700;
  font-variant-numeric: tabular-nums lining-nums;
  font-feature-settings: "tnum" 1, "lnum" 1;
}

/* Answer badge */
.problem .answer {
  color: #ffffff;
  font-weight: 700;
  background: linear-gradient(135deg, var(--site-accent, #22c55e), var(--site-accent-hover, #16a34a));
  border: none;
  border-radius: var(--radius-md, 10px);
}

/* Show answers state */
.show-answers .problem {
  background: linear-gradient(135deg, #f8f9ff 0%, var(--site-primary-light, #eef2ff) 100%);
  border-left-color: var(--site-primary, #4f46e5);
}

/* ═══ Variant Chip ═══ */
.variant-chip {
  font-size: var(--text-xs, 0.75rem);
  font-weight: 700;
  letter-spacing: 0.06em;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-pill);
  color: var(--site-primary, #4f46e5);
  background: var(--site-primary-light, #eef2ff);
  border: 1px solid var(--site-primary-border, #c7d2fe);
  text-transform: uppercase;
  font-variant-numeric: tabular-nums;
}

.variant-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 0.3rem 0 0.9rem;
}

/* ═══ Category Cards ═══ */
.section-header { margin: 1.5rem 0 1rem; }

.section-header h2 {
  font-family: var(--font-heading);
  font-size: var(--text-2xl, 1.5rem);
  font-weight: 800;
  color: var(--site-text, #111827);
  letter-spacing: -0.02em;
}

.section-header h2::after {
  content: '';
  display: block;
  width: 48px;
  height: 3px;
  margin-top: 0.45rem;
  background: linear-gradient(90deg, var(--site-primary, #4f46e5), var(--site-accent, #22c55e));
  border-radius: 2px;
}

.section-header p { color: var(--site-text-muted, #6b7280); margin-top: 0.25rem; }
.categories-section { padding: 0 0.5rem; }

.categories-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
  margin: 1rem 0;
}

.category-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.5rem;
  padding: 1.75rem;
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-card, 14px);
  box-shadow: var(--shadow-sm);
  text-decoration: none;
  color: inherit;
  position: relative;
  overflow: hidden;
  transition: transform var(--dur-normal) var(--ease-default),
              box-shadow var(--dur-normal) var(--ease-default),
              border-color var(--dur-normal) var(--ease-default);
}

/* Bottom accent bar animation */
.category-card::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  right: 50%;
  height: 3px;
  background: linear-gradient(90deg, var(--site-primary, #4f46e5), var(--site-accent, #22c55e));
  border-radius: 0 0 var(--radius-card) var(--radius-card);
  transition: left var(--dur-normal) var(--ease-default),
              right var(--dur-normal) var(--ease-default);
}

.category-card:hover::after { left: 0; right: 0; }

.category-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--site-primary, #4f46e5);
}

.category-icon {
  font-size: 2.25rem;
  line-height: 1;
  transition: transform var(--dur-normal) var(--ease-default);
}

.category-card:hover .category-icon { transform: scale(1.08); }

.category-card h3 {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--site-primary-dark, #312e81);
  letter-spacing: -0.015em;
  margin: 0;
}

.category-card p {
  font-size: var(--text-sm, 0.875rem);
  color: var(--site-text-muted, #6b7280);
  line-height: 1.5;
  margin: 0;
}

.category-meta {
  font-size: var(--text-xs, 0.75rem);
  font-weight: 700;
  color: var(--site-primary, #4f46e5);
  margin-top: auto;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-family: var(--font-heading);
}

/* ═══ Subcategory Cards ═══ */
.subcategories-section { margin: 1.5rem 0; }
.difficulty-icon { font-size: 1.3rem; }

.subcategories-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
}

.subcategory-card {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  padding: 1.375rem 1.25rem;
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-card, 14px);
  text-decoration: none;
  color: inherit;
  position: relative;
  overflow: hidden;
  transition: transform var(--dur-normal) var(--ease-default),
              box-shadow var(--dur-normal) var(--ease-default),
              border-color var(--dur-normal) var(--ease-default);
}

.subcategory-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--site-primary, #4f46e5), var(--site-accent, #22c55e));
  transform: scaleX(0);
  transition: transform var(--dur-normal) var(--ease-default);
}

.subcategory-card:hover::before { transform: scaleX(1); }

.subcategory-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--site-primary, #4f46e5);
}

.subcategory-card h3 {
  font-family: var(--font-heading);
  font-weight: 700;
  color: var(--site-text, #111827);
  font-size: 1.05rem;
  letter-spacing: -0.01em;
}

.subcategory-card p {
  font-size: var(--text-sm, 0.875rem);
  color: var(--site-text-muted, #6b7280);
}

.subcategory-arrow {
  font-size: var(--text-xs, 0.75rem);
  font-weight: 700;
  color: var(--site-primary, #4f46e5);
  margin-top: auto;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-family: var(--font-heading);
}

/* ═══ Worksheet Grid ═══ */
.worksheets-section { margin: 1.5rem 0; }

.worksheets-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 0.75rem;
}

.worksheet-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
  padding: 1rem 0.75rem;
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-bottom: 3px solid var(--site-primary, #4f46e5);
  border-radius: var(--radius-md, 10px);
  text-decoration: none;
  color: inherit;
  text-align: center;
  transition: transform var(--dur-fast) var(--ease-default),
              box-shadow var(--dur-fast) var(--ease-default),
              border-color var(--dur-fast) var(--ease-default),
              background var(--dur-fast) var(--ease-default);
}

.worksheet-card:hover {
  border-bottom-color: var(--site-accent, #22c55e);
  background: var(--site-primary-light, #eef2ff);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.worksheet-number {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.375rem;
  color: var(--site-primary, #4f46e5);
  width: 2.4rem;
  height: 2.4rem;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--site-primary-light, #eef2ff);
  border-radius: 50%;
  font-variant-numeric: tabular-nums lining-nums;
  font-feature-settings: "tnum" 1, "lnum" 1;
}

.worksheet-card h3 {
  font-size: var(--text-xs, 0.75rem);
  margin: 0;
  color: var(--site-text, #111827);
  font-weight: 600;
}

.worksheet-problems {
  font-size: var(--text-xs, 0.75rem);
  color: #9ca3af;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  font-weight: 600;
}

/* ═══ Worksheet Content (detail page) ═══ */
.worksheet-content {
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  box-shadow: var(--detail-card-shadow);
}

.worksheet-header {
  border-bottom: 2px solid var(--site-primary-light, #eef2ff);
}

.worksheet-title {
  font-family: var(--font-heading);
  font-size: 1.375rem;
  font-weight: 800;
  color: var(--site-primary-dark, #312e81);
  letter-spacing: -0.02em;
}

.worksheet-meta {
  font-size: var(--text-sm, 0.875rem);
  font-weight: 600;
  color: var(--site-primary, #4f46e5);
  background: var(--site-primary-light, #eef2ff);
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  box-shadow: var(--shadow-sm);
}

/* ═══ Content Toggle ═══ */
.body-content--collapsible {
  margin: 1rem 0;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-card, 14px);
  overflow: hidden;
}

.content-toggle {
  border: 1px solid var(--site-primary-border, #c7d2fe);
  background: #ffffff;
}

.content-toggle summary {
  padding: 0.9rem 1.25rem;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--site-primary-dark, #312e81);
  cursor: pointer;
  background: var(--site-primary-light, #eef2ff);
  border-bottom: 1px solid transparent;
  transition: background var(--dur-fast) var(--ease-default);
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.content-toggle summary::-webkit-details-marker { display: none; }

.content-toggle summary::before {
  content: '▶';
  display: inline-block;
  margin-right: 0.5rem;
  font-size: 0.7em;
  transition: transform var(--dur-normal) var(--ease-default);
  color: var(--site-primary, #4f46e5);
}

.content-toggle[open] summary::before { transform: rotate(90deg); }
.content-toggle summary:hover { background: #e0e7ff; }
.content-toggle[open] summary { border-bottom-color: var(--site-primary-border, #c7d2fe); }

.content-toggle-panel { padding: 1.25rem 1.5rem; border-top: 1px solid var(--site-border, #e5e7eb); }

.content-toggle-panel h2 {
  font-family: var(--font-heading);
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--site-primary-dark, #312e81);
  margin: 1rem 0 0.5rem;
}

.content-toggle-panel h3 {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--site-primary-hover, #4338ca);
  margin: 0.75rem 0 0.4rem;
}

.content-toggle-panel p  { line-height: 1.7; color: #374151; margin: 0.4rem 0; }
.content-toggle-panel ul,
.content-toggle-panel ol { padding-left: 1.25rem; margin: 0.5rem 0; color: #374151; }
.content-toggle-panel li { margin: 0.3rem 0; line-height: 1.6; }
.content-toggle-panel strong { color: var(--site-primary-dark, #312e81); }

/* ═══ Score Panel ═══ */
.score-panel {
  display: none;
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-card, 14px);
  padding: 1.25rem 1.5rem;
  margin-top: 1rem;
  transition: all var(--dur-normal) var(--ease-default);
}

.score-panel.score-visible {
  display: block;
  animation: scoreSlide 300ms var(--ease-out);
}

@keyframes scoreSlide {
  from { opacity: 0; transform: translateX(-20px); }
  to   { opacity: 1; transform: translateX(0); }
}

.score-inner {
  position: relative;
  background: #ffffff;
  border: 2px solid var(--site-primary-border, #c7d2fe);
  box-shadow: var(--shadow-sm);
}

.score-inner::after {
  content: "";
  display: block;
  height: 6px;
  margin-top: 0.75rem;
  background: linear-gradient(90deg, var(--site-primary, #4f46e5), var(--site-accent, #22c55e));
  border-radius: 3px;
  overflow: hidden;
}

.score-icon { font-size: 1.5rem; line-height: 1; }
.score-detail { font-size: 1rem; font-weight: 600; color: var(--site-text, #111827); }
.score-text { font-size: 1.1rem; font-weight: 600; color: var(--site-text, #111827); }
.score-text strong { color: var(--site-primary, #4f46e5); }
.score-label { color: var(--site-text-muted, #6b7280); font-size: 0.9rem; }

.score-pct {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--site-primary, #4f46e5);
  font-variant-numeric: tabular-nums lining-nums;
  font-feature-settings: "tnum" 1, "lnum" 1;
}

/* ═══ Content Section ═══ */
.content-section {
  padding: 1.5rem;
  margin: 1rem 0;
  background: #ffffff;
  border: 1px solid var(--site-primary-border, #c7d2fe);
  box-shadow: var(--shadow-sm);
}

.content-section h2 {
  font-family: var(--font-heading);
  color: var(--site-primary-dark, #312e81);
  font-weight: 700;
  margin-bottom: 0.75rem;
  border-bottom: 1px solid var(--site-primary-light, #eef2ff);
}

.content-section h3 {
  font-family: var(--font-heading);
  color: var(--site-primary-hover, #4338ca);
  font-weight: 600;
  letter-spacing: -0.01em;
}

.content-section p { line-height: 1.7; color: #374151; }
.content-section strong { color: var(--site-primary-dark, #312e81); font-weight: 600; }

.content-section a,
.intro a {
  color: var(--site-primary, #4f46e5);
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
  text-decoration-color: color-mix(in srgb, var(--site-primary) 40%, transparent);
}

.content-section a:hover,
.intro a:hover {
  text-decoration-color: var(--site-primary, #4f46e5);
}

/* ═══ Interactive Answer Input ═══ */
.answer-input {
  border: 2px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-md, 10px);
  background: #ffffff;
  color: var(--site-text, #111827);
  font-family: var(--font-mono);
  font-size: var(--text-lg, 1.125rem);
  font-weight: 700;
  transition: border-color var(--dur-normal) var(--ease-default),
              box-shadow var(--dur-normal) var(--ease-default),
              background var(--dur-normal) var(--ease-default);
}

.answer-input:focus {
  border-color: var(--site-primary, #4f46e5);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.12);
  background: var(--site-primary-light, #eef2ff);
}

.answer-input::placeholder { color: #9ca3af; font-weight: 400; }

/* Problem states */
.problem.is-correct .answer-input {
  border-color: var(--site-accent, #22c55e);
  background: var(--color-success-bg, #f0fdf4);
  color: var(--color-success-text, #166534);
  box-shadow: 0 0 0 3px rgba(34, 197, 94, 0.12);
}

.problem.is-wrong .answer-input {
  border-color: var(--color-error, #ef4444);
  background: var(--color-error-bg, #fef2f2);
  color: var(--color-error-text, #991b1b);
  box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.12);
}

.problem.is-empty .answer-input {
  border-color: var(--color-warning, #f59e0b);
  background: var(--color-warning-bg, #fffbeb);
}

.problem.is-correct {
  border-left-color: var(--site-accent, #22c55e) !important;
  background: linear-gradient(135deg, #f0fdf4 0%, #dcfce7 100%) !important;
}

.problem.is-wrong {
  border-left-color: var(--color-error, #ef4444) !important;
  background: linear-gradient(135deg, #fef2f2 0%, #fee2e2 100%) !important;
}

/* When show-answers is active, hide inputs */
.show-answers .answer-input { display: none; }

/* ═══ Score Retry Button ═══ */
.score-retry {
  background: var(--site-primary-light, #eef2ff);
  color: var(--site-primary, #4f46e5);
  border: 2px solid var(--site-primary-border, #c7d2fe);
  cursor: pointer;
  transition: all var(--dur-fast) var(--ease-default);
}

.score-retry:hover {
  background: var(--site-primary, #4f46e5);
  color: #ffffff;
  border-color: var(--site-primary-hover, #4338ca);
  transform: translateY(-1px);
}

/* ═══ Utility Animations ═══ */
@keyframes fadeIn    { from { opacity: 0; } to { opacity: 1; } }
@keyframes slideUp   { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
@keyframes fadeInUp  { from { opacity: 0; transform: translateY(16px); } to { opacity: 1; transform: translateY(0); } }

.fade-in  { animation: fadeIn  300ms var(--ease-out); }
.slide-up { animation: slideUp 300ms var(--ease-out); }

/* Staggered card entrance */
.category-card,
.subcategory-card,
.worksheet-card,
.seo-block {
  animation: fadeInUp 350ms var(--ease-out) both;
}

.category-card:nth-child(1),  .subcategory-card:nth-child(1),  .worksheet-card:nth-child(1),  .seo-block:nth-child(1)  { animation-delay:   0ms; }
.category-card:nth-child(2),  .subcategory-card:nth-child(2),  .worksheet-card:nth-child(2),  .seo-block:nth-child(2)  { animation-delay:  50ms; }
.category-card:nth-child(3),  .subcategory-card:nth-child(3),  .worksheet-card:nth-child(3),  .seo-block:nth-child(3)  { animation-delay: 100ms; }
.category-card:nth-child(4),  .subcategory-card:nth-child(4),  .worksheet-card:nth-child(4),  .seo-block:nth-child(4)  { animation-delay: 150ms; }
.category-card:nth-child(5),  .subcategory-card:nth-child(5),  .worksheet-card:nth-child(5),  .seo-block:nth-child(5)  { animation-delay: 200ms; }
.category-card:nth-child(n+6),.subcategory-card:nth-child(n+6),.worksheet-card:nth-child(n+6),.seo-block:nth-child(n+6) { animation-delay: 250ms; }

/* ═══ SEO Components ═══ */
.seo-components { margin: 1.5rem 0; border-top: 1px solid var(--site-primary-light, #eef2ff); padding-top: 1rem; }
.seo-components--primary { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.2rem; }
.seo-components--secondary { margin-top: 1rem; }
.seo-more-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1.2rem; }

.seo-block {
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-card, 14px);
  padding: 1.25rem 1.375rem;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--dur-normal) var(--ease-default),
              transform var(--dur-normal) var(--ease-default);
}

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

/* SEO Card — header band */
.seo-card {
  background: #ffffff;
  border-color: var(--site-border, #e5e7eb);
  border-top: none;
}

.seo-card::before {
  content: '';
  display: block;
  height: 4px;
  border-radius: 2px;
  margin-bottom: 0.875rem;
  background: var(--site-primary, #4f46e5);
}

.seo-card:hover {
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.12);
}

/* Card band — primary/accent alternating */
.seo-card.features::before        { background: var(--site-primary, #4f46e5); }
.seo-card.benefits::before        { background: var(--site-accent, #22c55e); }
.seo-card.faq::before             { background: var(--site-primary-hover, #4338ca); }
.seo-card.tips::before            { background: var(--site-accent, #22c55e); }
.seo-card.steps::before           { background: var(--site-primary, #4f46e5); }
.seo-card.tutorial::before        { background: var(--site-accent, #22c55e); }
.seo-card.examples::before        { background: var(--site-primary-hover, #4338ca); }
.seo-card.use-cases::before       { background: var(--site-accent, #22c55e); }
.seo-card.common-mistakes::before { background: #f59e0b; }
.seo-card.practice::before        { background: var(--site-accent, #22c55e); }
.seo-card.requirements::before    { background: var(--site-primary-hover, #4338ca); }
.seo-card.resources::before       { background: var(--site-accent, #22c55e); }
.seo-card.next-steps::before      { background: var(--site-primary, #4f46e5); }
.seo-card.summary::before         { background: var(--site-accent, #22c55e); }
.seo-card.related::before         { background: var(--site-primary-hover, #4338ca); }

/* Secondary seo-blocks: left-bar */
.seo-components--secondary .seo-block { background: var(--site-primary-light, #eef2ff); }
.seo-block.tutorial      { border-left: 3px solid var(--site-primary, #4f46e5); }
.seo-block.examples      { border-left: 3px solid var(--site-accent, #22c55e); }
.seo-block.use-cases     { border-left: 3px solid var(--site-primary-hover, #4338ca); }
.seo-block.common-mistakes { border-left: 3px solid #f59e0b; }
.seo-block.practice      { border-left: 3px solid var(--site-accent, #22c55e); }
.seo-block.requirements  { border-left: 3px solid var(--site-primary-hover, #4338ca); }
.seo-block.resources     { border-left: 3px solid var(--site-accent, #22c55e); }
.seo-block.next-steps    { border-left: 3px solid #f59e0b; }
.seo-block.summary       { border-left: 3px solid var(--site-primary, #4f46e5); }
.seo-block.related       { border-left: 3px solid var(--site-accent, #22c55e); }

/* SEO block typography */
.seo-block h2 {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--site-primary-dark, #312e81);
  margin: 0 0 0.6rem;
  letter-spacing: -0.01em;
}

.seo-block h3 {
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 600;
  color: var(--site-primary-hover, #4338ca);
  margin: 0.6rem 0 0.4rem;
  letter-spacing: -0.01em;
}

.seo-block h4 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--site-primary, #4f46e5);
  margin: 0.5rem 0 0.3rem;
}

.seo-block p {
  font-size: 0.92rem;
  line-height: 1.7;
  color: #374151;
  margin: 0.35rem 0;
  max-width: 68ch;
}

.seo-block ul,
.seo-block ol { padding-left: 1.2rem; margin: 0.4rem 0; }

.seo-block li {
  font-size: 0.92rem;
  line-height: 1.6;
  color: #374151;
  margin: 0.25rem 0;
}

.seo-block strong { color: var(--site-primary-dark, #312e81); }

.seo-block a {
  color: var(--site-primary, #4f46e5);
  text-decoration: none;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
  text-decoration-color: color-mix(in srgb, var(--site-primary) 40%, transparent);
}

.seo-block a:hover {
  text-decoration: underline;
  text-decoration-color: var(--site-primary, #4f46e5);
}

.seo-block blockquote {
  border-left: 3px solid var(--site-primary, #4f46e5);
  padding: 0.75rem 1.25rem;
  margin: 1rem 0;
  font-style: italic;
  color: var(--site-text-muted, #6b7280);
  background: color-mix(in srgb, var(--site-primary) 4%, white);
  border-radius: 0 var(--radius-sm, 6px) var(--radius-sm, 6px) 0;
}

/* FAQ details */
.seo-block details { border-bottom: 1px solid var(--site-primary-border, #c7d2fe); padding: 0.5rem 0; }
.seo-block details:last-child { border-bottom: none; }

.seo-block details summary {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.92rem;
  cursor: pointer;
  list-style: none;
  color: var(--site-primary-hover, #4338ca);
  letter-spacing: -0.01em;
  line-height: 1.4;
}

.seo-block details summary::-webkit-details-marker { display: none; }

.seo-block details summary::before {
  content: "▸";
  margin-right: 0.4rem;
  color: var(--site-primary, #4f46e5);
  display: inline-block;
  transition: transform var(--dur-fast) var(--ease-default);
}

.seo-block details[open] summary::before { transform: rotate(90deg); }
.seo-block details p { padding: 0.3rem 0 0.3rem 1rem; color: #4b5563; font-size: 0.88rem; line-height: 1.7; max-width: 60ch; }

/* ═══ Page Navigation ═══ */
.page-navigation {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem;
  margin-top: 1.5rem;
  padding: 1.25rem;
  background: #ffffff;
  border: 1.5px solid var(--site-primary-border, #c7d2fe);
  border-radius: var(--radius-xl, 20px);
  box-shadow: var(--shadow-sm);
}

.btn-nav {
  display: inline-flex;
  align-items: center;
  padding: 0.625rem 1.125rem;
  border-radius: var(--radius-md, 10px);
  color: var(--site-primary, #4f46e5);
  border: 2px solid var(--site-primary-border, #c7d2fe);
  text-decoration: none;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.9375rem;
  box-shadow: var(--shadow-sm);
  transition: background var(--dur-normal) var(--ease-default),
              border-color var(--dur-normal) var(--ease-default),
              transform var(--dur-normal) var(--ease-default),
              box-shadow var(--dur-normal) var(--ease-default);
}

.btn-nav:hover {
  background: var(--site-primary-light, #eef2ff);
  border-color: var(--site-primary, #4f46e5);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
  text-decoration: none;
}

.btn-nav.disabled {
  color: var(--site-border-dark, #d1d5db);
  cursor: not-allowed;
  opacity: 0.5;
  transform: none;
}

.btn-nav.disabled:hover {
  background: transparent;
  border-color: var(--site-border-dark, #d1d5db);
  box-shadow: none;
  transform: none;
}

.btn-nav.back-to-list {
  background: linear-gradient(135deg, var(--site-primary, #4f46e5) 0%, var(--site-primary-hover, #4338ca) 100%);
  color: #ffffff;
  border-color: var(--site-primary-hover, #4338ca);
  box-shadow: var(--shadow-brand);
}

.btn-nav.back-to-list:hover {
  background: linear-gradient(135deg, var(--site-primary-hover, #4338ca) 0%, var(--site-primary-dark, #312e81) 100%);
  border-color: var(--site-primary-dark, #312e81);
  box-shadow: var(--shadow-xl);
  transform: translateY(-2px);
}

/* ═══ Homepage / Static Pages ═══ */
.homepage > .content {
  background: #ffffff;
  border: 1px solid var(--site-primary-border, #c7d2fe);
  box-shadow: var(--shadow-sm);
}

.homepage > .content h2 {
  font-family: var(--font-heading);
  color: var(--site-primary-dark, #312e81);
  border-bottom-color: var(--site-primary-light, #eef2ff);
  font-weight: 700;
}

.homepage > .content p  { color: var(--site-text-light, #4b5563); }
.homepage > .content li { color: var(--site-text-light, #4b5563); }

.static-page .page-header { padding: 2.5rem 2.5rem 2rem; }

.static-page .content {
  background: #ffffff;
  border: 1px solid var(--site-primary-border, #c7d2fe);
  box-shadow: var(--shadow-sm);
}

.static-page .content h2 {
  font-family: var(--font-heading);
  color: var(--site-primary-dark, #312e81);
  font-size: var(--text-2xl, 1.5rem);
  font-weight: 700;
  border-bottom: 2px solid var(--site-primary-light, #eef2ff);
}

.static-page .content p   { color: var(--site-text, #111827); font-size: 0.9375rem; }
.static-page .content ul  { color: var(--site-text, #111827); }
.static-page .content strong { color: var(--site-primary, #4f46e5); font-weight: 600; }

/* ═══ Variant Themes (detail page) ═══ */
:root {
  --detail-bg-gradient-start: #f5f3ff;
  --detail-bg-gradient-end:   #eef2ff;
  --detail-card-shadow:       0 2px 8px rgba(79, 70, 229, 0.08);
  --detail-card-shadow-hover: 0 10px 28px rgba(79, 70, 229, 0.16);
  --detail-theme-primary:     var(--site-primary, #4f46e5);
  --detail-theme-secondary:   var(--site-primary-hover, #4338ca);
  --detail-theme-soft:        var(--site-primary-light, #eef2ff);
  --detail-theme-border:      var(--site-primary-border, #c7d2fe);
}

.detail-page.variant-theme-1 {
  --detail-theme-primary:   #4f46e5;
  --detail-theme-secondary: #4338ca;
  --detail-theme-soft:      #eef2ff;
  --detail-theme-border:    #c7d2fe;
}

.detail-page.variant-theme-2 {
  --detail-theme-primary:   #0d9488;
  --detail-theme-secondary: #0f766e;
  --detail-theme-soft:      #f0fdfa;
  --detail-theme-border:    #99f6e4;
}

.detail-page.variant-theme-3 {
  --detail-theme-primary:   #7c3aed;
  --detail-theme-secondary: #6d28d9;
  --detail-theme-soft:      #f5f3ff;
  --detail-theme-border:    #ddd6fe;
}

.detail-page.variant-theme-4 {
  --detail-theme-primary:   #ea580c;
  --detail-theme-secondary: #c2410c;
  --detail-theme-soft:      #fff7ed;
  --detail-theme-border:    #fed7aa;
}

.detail-page.variant-theme-5 {
  --detail-theme-primary:   #be123c;
  --detail-theme-secondary: #9f1239;
  --detail-theme-soft:      #fff1f2;
  --detail-theme-border:    #fecdd3;
}

/* ═══ Dark Mode ═══ */
@media (prefers-color-scheme: dark) {
  body {
    background: linear-gradient(160deg, #0a0a1a 0%, #12102e 50%, #071a0f 100%);
    background-attachment: fixed;
    color: #e5e7eb;
  }

  .hero {
    background: linear-gradient(160deg, #12102e 0%, #0a0a1a 60%, #071a0f 100%);
    border-bottom-color: rgba(79, 70, 229, 0.4);
  }

  .hero::before { background: radial-gradient(circle, rgba(79, 70, 229, 0.15) 0%, transparent 70%); }
  .hero::after  { background: radial-gradient(circle, rgba(34, 197, 94, 0.10) 0%, transparent 70%); }
  .hero h1      { color: #e0e7ff; }
  .hero .subtitle { color: #a5b4fc; }

  .page-header {
    background: #12102e;
    border-bottom-color: rgba(79, 70, 229, 0.3);
  }

  .page-header h1   { color: #e0e7ff; }
  .page-header .subtitle { color: #a5b4fc; }

  .breadcrumb {
  }
  .breadcrumb ol { color: #9ca3af; }
  .breadcrumb a  { color: #818cf8; }
  .breadcrumb li:last-child { color: #e5e7eb; }

  .stat-item {
    background: rgba(79, 70, 229, 0.08);
    border-color: rgba(79, 70, 229, 0.25);
  }
  .stat-number { color: #818cf8; }
  .stat-label  { color: #9ca3af; }

  .category-card,
  .subcategory-card,
  .worksheet-card {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.25);
    color: #e5e7eb;
  }

  .category-card:hover,
  .subcategory-card:hover,
  .worksheet-card:hover {
    background: #1e1b4b;
    border-color: rgba(79, 70, 229, 0.5);
    box-shadow: 0 12px 28px rgba(0, 0, 0, 0.5);
  }

  .category-card h3,
  .subcategory-card h3 { color: #e0e7ff; }
  .category-card p,
  .subcategory-card p  { color: #9ca3af; }
  .category-meta,
  .subcategory-arrow   { color: #818cf8; }
  .worksheet-number    { background: rgba(79, 70, 229, 0.15); color: #818cf8; }
  .worksheet-card h3   { color: #e5e7eb; }

  .body-content {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.2);
  }
  .body-content h2 { color: #a5b4fc; border-bottom-color: rgba(79, 70, 229, 0.2); }
  .body-content p,
  .body-content ul,
  .body-content ol { color: #d1d5db; }
  .body-content li strong { color: #818cf8; }

  .set-switcher {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.25);
  }
  .set-btn {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.25);
    color: #e5e7eb;
  }
  .set-btn:hover { background: #1e1b4b; border-color: #4f46e5; }
  .set-btn.active { background: linear-gradient(135deg, #4f46e5, #4338ca); color: #fff; }

  .btn {
    background: #1a1a2e;
    color: #e5e7eb;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  }

  .intro,
  .intro-section {
    background: linear-gradient(135deg, #12102e 0%, #1a1a2e 100%);
    border-color: rgba(79, 70, 229, 0.25);
  }
  .intro h3,
  .intro-section h3 { color: #a5b4fc; }
  .intro p,
  .intro-section p  { color: #d1d5db; }

  .content-toggle { background: #1a1a2e; border-color: rgba(79, 70, 229, 0.2); }
  .content-toggle summary { background: #12102e; color: #a5b4fc; }
  .content-toggle summary:hover { background: #1e1b4b; }
  .content-toggle-panel { background: #1a1a2e; border-top-color: rgba(79, 70, 229, 0.15); }
  .content-toggle-panel h2 { color: #a5b4fc; }
  .content-toggle-panel h3 { color: #818cf8; }
  .content-toggle-panel p  { color: #d1d5db; }
  .content-toggle-panel strong { color: #a5b4fc; }

  .score-panel  { background: #1a1a2e; border-color: rgba(79, 70, 229, 0.25); }
  .score-inner  { background: #1a1a2e; border-color: rgba(79, 70, 229, 0.25); }
  .score-inner::after { background: linear-gradient(90deg, rgba(79,70,229,0.4), rgba(34,197,94,0.3)); }
  .score-text   { color: #e5e7eb; }
  .score-text strong { color: #818cf8; }
  .score-pct    { color: #818cf8; }

  .content-section {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.18);
    box-shadow: none;
  }
  .content-section h2 { color: #a5b4fc; border-bottom-color: rgba(79, 70, 229, 0.2); }
  .content-section h3 { color: #818cf8; }
  .content-section p  { color: #d1d5db; }
  .content-section strong { color: #a5b4fc; }

  .seo-block {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.2);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.35);
  }
  .seo-block:hover { box-shadow: 0 8px 24px rgba(0, 0, 0, 0.55); }
  .seo-components--secondary .seo-block { background: #12102e; }
  .seo-block h2 { color: #a5b4fc; }
  .seo-block h3 { color: #818cf8; }
  .seo-block p,
  .seo-block li { color: #d1d5db; }
  .seo-block strong { color: #a5b4fc; }
  .seo-block a  { color: #818cf8; }
  .seo-block details { border-bottom-color: rgba(79, 70, 229, 0.2); }
  .seo-block details summary { color: #a5b4fc; }
  .seo-block details p { color: #b0b5bd; }
  .seo-block blockquote { background: rgba(79, 70, 229, 0.08); color: #9ca3af; }

  .page-navigation {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.25);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  }
  .btn-nav { color: #818cf8; border-color: rgba(79, 70, 229, 0.25); }
  .btn-nav:hover { background: #1e1b4b; border-color: #4f46e5; }
  .btn-nav.back-to-list { background: linear-gradient(135deg, #4f46e5, #4338ca); color: #fff; border-color: #4338ca; }
  .btn-nav.back-to-list:hover { background: linear-gradient(135deg, #4338ca, #312e81); }

  .answer-input {
    background: #12102e;
    border-color: rgba(79, 70, 229, 0.25);
    color: #e5e7eb;
  }
  .answer-input:focus {
    border-color: #4f46e5;
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.2);
    background: #1e1b4b;
  }

  .problem { color: #e5e7eb; border-left-color: rgba(79, 70, 229, 0.5); }
  .problem .num    { background: rgba(79, 70, 229, 0.15); color: #818cf8; }
  .problem .answer { background: rgba(34, 197, 94, 0.18); color: #4ade80; }
  .show-answers .problem { background: linear-gradient(135deg, #12102e 0%, #1e1b4b 100%); }

  .variant-chip {
    background: rgba(79, 70, 229, 0.12);
    color: #818cf8;
    border-color: rgba(79, 70, 229, 0.3);
  }

  .worksheet-content { background: #1a1a2e; border-color: rgba(79, 70, 229, 0.25); }
  .worksheet-header  { border-bottom-color: rgba(79, 70, 229, 0.2); }
  .worksheet-title   { color: #a5b4fc; }
  .worksheet-meta    { background: rgba(79, 70, 229, 0.12); border-color: rgba(79, 70, 229, 0.25); color: #818cf8; }

  .homepage > .content,
  .static-page .content {
    background: #1a1a2e;
    border-color: rgba(79, 70, 229, 0.18);
    box-shadow: none;
  }
  .homepage > .content h2,
  .static-page .content h2 { color: #a5b4fc; border-bottom-color: rgba(79, 70, 229, 0.2); }
  .homepage > .content p,
  .homepage > .content li,
  .static-page .content p,
  .static-page .content ul { color: #d1d5db; }
  .static-page .content strong { color: #818cf8; }

  .section-header h2  { color: #e5e7eb; }
  .section-header p   { color: #9ca3af; }
  .score-detail       { color: #e5e7eb; }
  .score-label        { color: #9ca3af; }

  ::selection { background: rgba(79, 70, 229, 0.35); color: #fff; }
  ::-moz-selection { background: rgba(79, 70, 229, 0.35); color: #fff; }
  ::-webkit-scrollbar-track { background: #12102e; }
  ::-webkit-scrollbar-thumb { border-color: #12102e; }
}

/* ═══ Print Styles ═══ */
.print-only { display: none; }

@media print {
  body { background: #fff !important; color: #000 !important; }
  .hero::before,
  .hero::after  { display: none !important; }
  .hero {
    background: #fff !important;
    border-bottom: 2px solid #4f46e5 !important;
    padding: 1rem !important;
  }
  .hero h1 { color: #312e81 !important; }

  .category-card,
  .subcategory-card,
  .worksheet-card,
  .seo-block {
    animation: none !important;
    box-shadow: none !important;
    break-inside: avoid;
  }

  .category-card::after { display: none !important; }
  .subcategory-card::before { display: none !important; }
  .page-navigation,
  .set-switcher,
  .score-retry { display: none !important; }
  .stat-item { background: #fff !important; border: 1pt solid #ccc !important; box-shadow: none !important; }
  .btn        { box-shadow: none !important; }
  .section-header h2::after { background: #4f46e5 !important; }
  .content-section { border: none !important; box-shadow: none !important; }

  * { box-shadow: none !important; text-shadow: none !important; }
  -webkit-print-color-adjust: exact;
  print-color-adjust: exact;
}

/* ═══ Responsive ═══ */
@media (max-width: 768px) {
  .hero { padding: 2.5rem 1.25rem 2rem; }
  .hero h1 { font-size: 1.875rem; }
  .hero .subtitle { max-width: 100%; font-size: 1rem; }
  .hero-stats { gap: 0.875rem; }
  .stat-number { font-size: 1.4rem; }
  .categories-grid { grid-template-columns: 1fr; }
  .subcategories-grid { grid-template-columns: 1fr; }
  .worksheets-grid { grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); }
  .seo-components--primary { grid-template-columns: 1fr; }
  .seo-more-grid { grid-template-columns: 1fr; }
  .page-navigation { flex-wrap: wrap; justify-content: center; }
}

@media (max-width: 480px) {
  .hero { padding: 2rem 1rem; }
  .hero h1 { font-size: 1.5rem; }
  .hero-stats { flex-direction: column; gap: 0.75rem; }
  .categories-grid { grid-template-columns: 1fr; }
  .subcategories-grid { grid-template-columns: 1fr; }
}