/* ==========================================================================
   RIMC THEME DESIGN SYSTEM v2.0 — PIXEL-PERFECT REGIMENTAL EDITION
   Zero Blue Palette: Emerald (Math), Burgundy (English), Bronze/Amber (GK),
   and Regimental Cypress (Main Hub).
   ========================================================================== */

:root {
  --rimc-primary: #165b4c;
  --rimc-primary-dark: #0d3d33;
  --rimc-primary-light: #1f7a67;
  --rimc-primary-soft: rgba(22, 91, 76, 0.08);
  --rimc-primary-glow: rgba(22, 91, 76, 0.22);
  --rimc-accent: #831843;
  --rimc-accent-soft: rgba(131, 24, 67, 0.08);
  --rimc-gold: #b45309;
  --rimc-gold-soft: rgba(180, 83, 9, 0.12);
  --rimc-text: #0f172a;
  --rimc-text-secondary: #334155;
  --rimc-text-muted: #64748b;
  --rimc-bg-card: #ffffff;
  --rimc-bg-subtle: #f8fafc;
  --rimc-bg-page: #f1f5f9;
  --rimc-border: #e2e8f0;
  --rimc-border-subtle: rgba(0, 0, 0, 0.06);
  --rimc-shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.04);
  --rimc-shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06), 0 1px 2px rgba(0, 0, 0, 0.04);
  --rimc-shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08), 0 2px 4px rgba(0, 0, 0, 0.04);
  --rimc-shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.1), 0 4px 8px rgba(0, 0, 0, 0.04);
  --rimc-header-bg: linear-gradient(135deg, rgba(22, 91, 76, 0.08) 0%, rgba(131, 24, 67, 0.04) 50%, rgba(180, 83, 9, 0.07) 100%);
  --rimc-header-border: rgba(22, 91, 76, 0.16);
  --radius-xl: 16px;
  --radius-lg: 12px;
  --radius-md: 8px;
  --radius-sm: 6px;
  --radius-full: 999px;
  --font-base: "DM Sans", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-smooth: 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Mathematics Subject Palette: Deep Forest Emerald & Jade */
body[data-subject="mathematics"] {
  --rimc-primary: #065f46;
  --rimc-primary-dark: #022c22;
  --rimc-primary-light: #047857;
  --rimc-primary-soft: rgba(6, 95, 70, 0.07);
  --rimc-primary-glow: rgba(6, 95, 70, 0.20);
  --rimc-accent: #b45309;
  --rimc-accent-soft: rgba(180, 83, 9, 0.08);
  --rimc-gold: #d97706;
  --rimc-gold-soft: rgba(217, 119, 6, 0.10);
  --rimc-header-bg: linear-gradient(135deg, rgba(6, 95, 70, 0.09) 0%, rgba(4, 120, 87, 0.04) 50%, rgba(217, 119, 6, 0.06) 100%);
  --rimc-header-border: rgba(6, 95, 70, 0.16);
}

/* English Subject Palette: Imperial Burgundy & Stately Wine */
body[data-subject="english"] {
  --rimc-primary: #831843;
  --rimc-primary-dark: #4c0519;
  --rimc-primary-light: #9f1239;
  --rimc-primary-soft: rgba(131, 24, 67, 0.07);
  --rimc-primary-glow: rgba(131, 24, 67, 0.20);
  --rimc-accent: #b45309;
  --rimc-accent-soft: rgba(180, 83, 9, 0.08);
  --rimc-gold: #d97706;
  --rimc-gold-soft: rgba(217, 119, 6, 0.10);
  --rimc-header-bg: linear-gradient(135deg, rgba(131, 24, 67, 0.09) 0%, rgba(159, 18, 57, 0.04) 50%, rgba(217, 119, 6, 0.06) 100%);
  --rimc-header-border: rgba(131, 24, 67, 0.16);
}

/* General Knowledge Subject Palette: Burnished Bronze & Warm Amber */
body[data-subject="general-knowledge"] {
  --rimc-primary: #92400e;
  --rimc-primary-dark: #451a03;
  --rimc-primary-light: #b45309;
  --rimc-primary-soft: rgba(146, 64, 14, 0.07);
  --rimc-primary-glow: rgba(146, 64, 14, 0.20);
  --rimc-accent: #166534;
  --rimc-accent-soft: rgba(22, 101, 52, 0.08);
  --rimc-gold: #b45309;
  --rimc-gold-soft: rgba(180, 83, 9, 0.10);
  --rimc-header-bg: linear-gradient(135deg, rgba(146, 64, 14, 0.09) 0%, rgba(180, 83, 9, 0.04) 50%, rgba(22, 101, 52, 0.06) 100%);
  --rimc-header-border: rgba(146, 64, 14, 0.16);
}

/* Dark Mode Global Base (No Blue!) */
body.dark-mode {
  --rimc-primary: #2dd4bf;
  --rimc-primary-dark: #14b8a6;
  --rimc-primary-light: #5eead4;
  --rimc-primary-soft: rgba(45, 212, 191, 0.12);
  --rimc-primary-glow: rgba(45, 212, 191, 0.25);
  --rimc-accent: #fb7185;
  --rimc-accent-soft: rgba(251, 113, 133, 0.12);
  --rimc-gold: #fbbf24;
  --rimc-gold-soft: rgba(251, 191, 36, 0.12);
  --rimc-text: #f1f5f9;
  --rimc-text-secondary: #cbd5e1;
  --rimc-text-muted: #94a3b8;
  --rimc-bg-card: #1e293b;
  --rimc-bg-subtle: #0f172a;
  --rimc-bg-page: #020617;
  --rimc-border: #334155;
  --rimc-border-subtle: rgba(255, 255, 255, 0.08);
  --rimc-shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.3);
  --rimc-shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.35);
  --rimc-shadow-md: 0 4px 14px rgba(0, 0, 0, 0.45);
  --rimc-shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.55);
  --rimc-header-bg: linear-gradient(135deg, rgba(45, 212, 191, 0.10) 0%, rgba(251, 113, 133, 0.05) 50%, rgba(251, 191, 36, 0.07) 100%);
  --rimc-header-border: rgba(45, 212, 191, 0.22);
}

/* Dark Mode Subject Overrides */
body.dark-mode[data-subject="mathematics"] {
  --rimc-primary: #34d399;
  --rimc-primary-dark: #059669;
  --rimc-primary-light: #6ee7b7;
  --rimc-primary-soft: rgba(52, 211, 153, 0.12);
  --rimc-primary-glow: rgba(52, 211, 153, 0.25);
  --rimc-accent: #fbbf24;
  --rimc-accent-soft: rgba(251, 191, 36, 0.12);
  --rimc-gold: #f59e0b;
  --rimc-gold-soft: rgba(245, 158, 11, 0.12);
  --rimc-header-bg: linear-gradient(135deg, rgba(52, 211, 153, 0.10) 0%, rgba(16, 185, 129, 0.05) 50%, rgba(251, 191, 36, 0.07) 100%);
  --rimc-header-border: rgba(52, 211, 153, 0.22);
}

body.dark-mode[data-subject="english"] {
  --rimc-primary: #fb7185;
  --rimc-primary-dark: #e11d48;
  --rimc-primary-light: #fda4af;
  --rimc-primary-soft: rgba(251, 113, 133, 0.12);
  --rimc-primary-glow: rgba(251, 113, 133, 0.25);
  --rimc-accent: #fbbf24;
  --rimc-accent-soft: rgba(251, 191, 36, 0.12);
  --rimc-gold: #f59e0b;
  --rimc-gold-soft: rgba(245, 158, 11, 0.12);
  --rimc-header-bg: linear-gradient(135deg, rgba(251, 113, 133, 0.10) 0%, rgba(244, 63, 94, 0.05) 50%, rgba(251, 191, 36, 0.07) 100%);
  --rimc-header-border: rgba(251, 113, 133, 0.22);
}

body.dark-mode[data-subject="general-knowledge"] {
  --rimc-primary: #fbbf24;
  --rimc-primary-dark: #d97706;
  --rimc-primary-light: #fde68a;
  --rimc-primary-soft: rgba(251, 191, 36, 0.12);
  --rimc-primary-glow: rgba(251, 191, 36, 0.25);
  --rimc-accent: #4ade80;
  --rimc-accent-soft: rgba(74, 222, 128, 0.12);
  --rimc-gold: #f59e0b;
  --rimc-gold-soft: rgba(245, 158, 11, 0.12);
  --rimc-header-bg: linear-gradient(135deg, rgba(251, 191, 36, 0.10) 0%, rgba(217, 119, 6, 0.05) 50%, rgba(74, 222, 128, 0.07) 100%);
  --rimc-header-border: rgba(251, 191, 36, 0.22);
}

/* Dark Mode Contrast Optimization for Active Controls */
body.dark-mode .main-tabs-nav .tab-btn.active,
body.dark-mode .q-solution-toggle.active,
body.dark-mode .sub-nav-item.active,
body.dark-mode .topic-nav-btn.next {
  color: #090d16 !important;
  font-weight: 800;
}

/* ==========================================================================
   BASE LAYOUT & OVERFLOW GUARD
   ========================================================================== */
html, body.exam-ui {
  max-width: 100%;
  overflow-x: clip;
}

.rimc-hub-container,
.topic-container,
.subject-container {
  max-width: 1080px;
  margin: 1.25rem auto 3.5rem;
  padding: 0 1.25rem;
  font-family: var(--font-base);
  animation: rimcFadeUp 0.4s ease-out;
  min-width: 0;
}

@keyframes rimcFadeUp {
  0% {
    opacity: 0;
    transform: translateY(12px);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==========================================================================
   BREADCRUMBS — Compact pill, proper spacing
   ========================================================================== */
.breadcrumbs {
  margin-bottom: 1.25rem;
  font-size: 0.8rem;
  color: var(--rimc-text-muted);
  background: var(--rimc-bg-card);
  display: inline-flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.35rem;
  padding: 0.4rem 1rem;
  border-radius: var(--radius-full);
  border: 1px solid var(--rimc-border);
  box-shadow: var(--rimc-shadow-xs);
  line-height: 1.4;
}
.breadcrumbs a {
  color: var(--rimc-primary);
  text-decoration: none;
  font-weight: 700;
  transition: color var(--transition-fast);
}
.breadcrumbs a:hover {
  color: var(--rimc-primary-light);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1.5px;
}
.breadcrumbs i {
  font-size: 0.6rem;
  color: var(--rimc-text-muted);
  opacity: 0.55;
}

/* ==========================================================================
   HERO HEADERS — Refined gradient glassmorphism
   ========================================================================== */
.rimc-header,
.topic-header,
.subject-header {
  background: var(--rimc-header-bg);
  border: 1px solid var(--rimc-header-border);
  border-radius: var(--radius-xl);
  padding: 2rem 1.75rem 2.25rem;
  margin-bottom: 1.5rem;
  text-align: center;
  position: relative;
  overflow: hidden;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: var(--rimc-shadow-sm);
}
.rimc-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.9rem;
  border-radius: var(--radius-full);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  background: var(--rimc-primary-soft);
  color: var(--rimc-primary);
  border: 1px solid var(--rimc-primary-glow);
  margin-bottom: 0.85rem;
}
.rimc-header h1,
.topic-header h1,
.subject-header h1 {
  font-family: var(--font-base);
  font-size: clamp(1.5rem, 3.2vw, 2.2rem);
  font-weight: 800;
  color: var(--rimc-text);
  margin-bottom: 0.6rem;
  line-height: 1.22;
  letter-spacing: -0.03em;
}
.rimc-header p,
.topic-header p,
.subject-header p {
  color: var(--rimc-text-secondary);
  font-size: clamp(0.88rem, 1.6vw, 0.98rem);
  line-height: 1.7;
  max-width: 780px;
  margin: 0 auto;
}
.rimc-meta-chips {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 1.15rem;
}
.rimc-chip {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.78rem;
  font-weight: 700;
  padding: 0.3rem 0.75rem;
  border-radius: var(--radius-full);
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  color: var(--rimc-text-secondary);
  box-shadow: var(--rimc-shadow-xs);
  transition: all var(--transition-fast);
}
.rimc-chip i {
  color: var(--rimc-primary);
  font-size: 0.78rem;
}

/* ==========================================================================
   SUBJECT NAVIGATION SWITCHER
   ========================================================================== */
.subject-nav {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.35rem;
  overflow-x: auto;
  padding: 0.25rem 0 0.5rem;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}
.subject-nav::-webkit-scrollbar {
  display: none;
}
.sub-nav-item {
  padding: 0.5rem 1.1rem;
  text-decoration: none;
  color: var(--rimc-text-muted);
  font-size: 0.84rem;
  font-weight: 700;
  border-radius: var(--radius-full);
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  transition: all var(--transition-smooth);
  white-space: nowrap;
  flex-shrink: 0;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  box-shadow: var(--rimc-shadow-xs);
}
.sub-nav-item:hover {
  color: var(--rimc-primary);
  background: var(--rimc-primary-soft);
  border-color: var(--rimc-primary);
  transform: translateY(-1px);
  box-shadow: var(--rimc-shadow-sm);
}
.sub-nav-item.active {
  background: var(--rimc-primary);
  color: #fff;
  border-color: var(--rimc-primary);
  box-shadow: 0 3px 12px var(--rimc-primary-glow);
}

/* ==========================================================================
   STICKY MAIN TABS NAVIGATION — Polished pill bar
   ========================================================================== */
.main-tabs-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  padding: 0.35rem;
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-full);
  margin-bottom: 1.5rem;
  position: sticky;
  top: 72px;
  z-index: 90;
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  box-shadow: var(--rimc-shadow-md);
  justify-content: center;
}
.main-tabs-nav .tab-btn {
  border: none;
  background: transparent;
  color: var(--rimc-text-muted);
  padding: 0.55rem 1.15rem;
  border-radius: var(--radius-full);
  cursor: pointer;
  font-weight: 700;
  font-size: 0.85rem;
  font-family: var(--font-base);
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  transition: all var(--transition-smooth);
  white-space: nowrap !important;
  flex: 0 0 auto !important;
  width: auto !important;
  min-width: max-content !important;
  height: auto !important;
  min-height: 0 !important;
  position: relative;
}
.main-tabs-nav .tab-btn i {
  font-size: 0.78rem;
  opacity: 0.8;
}
.main-tabs-nav .tab-btn:hover {
  background: var(--rimc-primary-soft);
  color: var(--rimc-primary);
}
.main-tabs-nav .tab-btn.active {
  background: var(--rimc-primary);
  color: #fff;
  box-shadow: 0 2px 8px var(--rimc-primary-glow);
}
.main-tabs-nav .tab-btn.active i {
  opacity: 1;
}

/* MathJax Accessibility */
mjx-assistive-mml {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  overflow: hidden !important;
  clip: rect(1px, 1px, 1px, 1px) !important;
}

/* ==========================================================================
   TAB PANELS — Smooth reveal
   ========================================================================== */
.tab-panel {
  display: none;
  animation: rimcFadeUp 0.3s ease-out;
  min-width: 0;
}
.tab-panel.active {
  display: block;
}

/* ==========================================================================
   CARD FOUNDATIONS — Consistent elevation, tight spacing
   ========================================================================== */
.theory-block,
.card-premium {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem 1.65rem;
  margin-bottom: 1.25rem;
  box-shadow: var(--rimc-shadow-sm);
  line-height: 1.72;
  color: var(--rimc-text-secondary);
  min-width: 0;
  word-wrap: break-word;
  overflow-wrap: break-word;
}
.theory-block h2,
.card-title {
  font-family: var(--font-base);
  font-size: 1.22rem;
  font-weight: 800;
  color: var(--rimc-text);
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.55rem;
  border-bottom: 2px solid var(--rimc-primary-soft);
  padding-bottom: 0.6rem;
  letter-spacing: -0.01em;
}
.theory-block h2 i,
.card-title i {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 8px;
  background: var(--rimc-primary-soft);
  color: var(--rimc-primary);
  font-size: 0.88rem;
  flex-shrink: 0;
}
.theory-subheading {
  font-family: var(--font-base);
  font-size: 1.04rem;
  font-weight: 800;
  color: var(--rimc-text);
  margin: 1.35rem 0 0.6rem;
  display: flex;
  align-items: center;
  gap: 0.45rem;
  letter-spacing: -0.005em;
}
.theory-subheading i {
  color: var(--rimc-primary);
  font-size: 0.88rem;
}

/* ==========================================================================
   FORMULAS — Clean card stack
   ========================================================================== */
.formula-showcase {
  background: var(--rimc-bg-subtle);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-lg);
  padding: 1.15rem;
  margin: 1.15rem 0;
}
.formula-card {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-left: 3.5px solid var(--rimc-primary);
  border-radius: var(--radius-md);
  padding: 0.9rem 1.15rem;
  margin-bottom: 0.75rem;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  min-width: 0;
  box-shadow: var(--rimc-shadow-xs);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.formula-card:hover {
  border-color: var(--rimc-primary-glow);
  box-shadow: var(--rimc-shadow-sm);
}
.formula-card:last-child {
  margin-bottom: 0;
}
.formula-label {
  font-weight: 800;
  color: var(--rimc-primary);
  font-size: 0.85rem;
  margin-bottom: 0.3rem;
  letter-spacing: 0.015em;
}
.formula-math {
  overflow-x: auto;
  max-width: 100%;
}

/* ==========================================================================
   CALLOUT CARDS — Exam Tips, Traps, Tricks
   ========================================================================== */
.exam-tip,
.cadet-strategy {
  padding: 1rem 1.25rem;
  border-radius: var(--radius-md);
  margin: 1rem 0;
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  font-size: 0.9rem;
  line-height: 1.62;
  background: var(--rimc-primary-soft);
  border-left: 3.5px solid var(--rimc-primary);
  color: var(--rimc-text);
  min-width: 0;
}
.rimc-descriptive-box {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-primary-glow);
  border-radius: var(--radius-lg);
  padding: 1.25rem 1.35rem;
  margin: 1.15rem 0;
  box-shadow: var(--rimc-shadow-xs);
}
.rimc-step {
  margin-bottom: 0.75rem;
  padding: 0.7rem 1rem 0.7rem 1.1rem;
  border-left: 3px solid var(--rimc-gold);
  background: var(--rimc-bg-subtle);
  border-radius: var(--radius-sm);
  min-width: 0;
  transition: background var(--transition-fast);
}
.rimc-step:hover {
  background: var(--rimc-gold-soft);
}
.rimc-step-title {
  font-weight: 800;
  color: var(--rimc-primary);
  font-size: 0.9rem;
  margin-bottom: 0.2rem;
}

/* ==========================================================================
   PREMIUM TABLES — Precise alignment & hover micro-interaction
   ========================================================================== */
.premium-table-container {
  width: 100%;
  max-width: 100%;
  overflow-x: auto;
  margin: 1.15rem 0;
  border-radius: var(--radius-md);
  border: 1px solid var(--rimc-border);
  box-shadow: var(--rimc-shadow-xs);
  background: var(--rimc-bg-card);
  -webkit-overflow-scrolling: touch;
}
.premium-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  text-align: left;
}
.premium-table th {
  background: var(--rimc-primary-soft);
  color: var(--rimc-primary);
  font-weight: 800;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.75rem 1rem;
  border-bottom: 2px solid var(--rimc-border);
  white-space: nowrap;
  position: sticky;
  top: 0;
}
.premium-table td {
  padding: 0.72rem 1rem;
  border-bottom: 1px solid var(--rimc-border-subtle);
  color: var(--rimc-text-secondary);
  line-height: 1.6;
  vertical-align: top;
}
.premium-table tr:last-child td {
  border-bottom: none;
}
.premium-table tbody tr {
  transition: background var(--transition-fast);
}
.premium-table tbody tr:hover td {
  background: var(--rimc-bg-subtle);
}

/* ==========================================================================
   TAGS & CHIPS — Consistent micro-badges
   ========================================================================== */
.syllabus-tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.85rem;
}
.syllabus-tag {
  font-size: 0.72rem;
  font-weight: 800;
  padding: 0.22rem 0.6rem;
  border-radius: var(--radius-sm);
  background: var(--rimc-primary-soft);
  color: var(--rimc-primary);
  border: 1px solid var(--rimc-primary-glow);
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}
.syllabus-tag i {
  font-size: 0.65rem;
}

/* ==========================================================================
   PRACTICE QUESTION CARDS — Elevated interaction design
   ========================================================================== */
.practice-q-card {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-lg);
  padding: 1.35rem 1.5rem;
  margin-bottom: 1rem;
  box-shadow: var(--rimc-shadow-xs);
  transition: all var(--transition-smooth);
  min-width: 0;
  word-wrap: break-word;
  overflow-wrap: break-word;
}
.practice-q-card:hover {
  border-color: var(--rimc-primary-glow);
  box-shadow: var(--rimc-shadow-md);
  transform: translateY(-1px);
}
.q-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
  gap: 0.5rem;
}
.q-badge {
  background: var(--rimc-primary-soft);
  color: var(--rimc-primary);
  font-weight: 800;
  font-size: 0.76rem;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
  border: 1px solid var(--rimc-primary-glow);
  letter-spacing: 0.02em;
}
.q-marks {
  font-size: 0.74rem;
  font-weight: 800;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
  background: var(--rimc-gold-soft);
  color: var(--rimc-gold);
  border: 1px solid var(--rimc-gold-soft);
}
.q-text {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--rimc-text);
  margin-bottom: 0.85rem;
  line-height: 1.65;
}
.q-solution-toggle {
  background: var(--rimc-bg-card);
  border: 1.5px solid var(--rimc-primary);
  color: var(--rimc-primary);
  font-weight: 700;
  font-size: 0.82rem;
  padding: 0.42rem 1.05rem;
  border-radius: var(--radius-full);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  transition: all var(--transition-smooth);
  box-shadow: var(--rimc-shadow-xs);
}
.q-solution-toggle:hover {
  background: var(--rimc-primary-soft);
  transform: translateY(-1px);
  box-shadow: var(--rimc-shadow-sm);
}
.q-solution-toggle.active {
  background: var(--rimc-primary);
  color: #fff;
  border-color: var(--rimc-primary);
  box-shadow: 0 3px 10px var(--rimc-primary-glow);
}
.q-solution-body {
  display: none;
  margin-top: 0.85rem;
  padding: 1.05rem 1.25rem;
  background: var(--rimc-bg-subtle);
  border-radius: var(--radius-md);
  border-left: 3.5px solid var(--rimc-primary);
  font-size: 0.9rem;
  line-height: 1.68;
  min-width: 0;
}
.q-solution-body.open {
  display: block;
  animation: rimcFadeUp 0.2s ease-out;
}

/* ==========================================================================
   TOPIC NAVIGATION FOOTER — Polished pagination buttons
   ========================================================================== */
.topic-nav-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.85rem;
  margin: 2rem 0;
  padding-top: 1.25rem;
  border-top: 1px solid var(--rimc-border);
}
.topic-nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.6rem 1.25rem;
  border-radius: var(--radius-full);
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  color: var(--rimc-text-secondary);
  font-size: 0.85rem;
  font-weight: 700;
  text-decoration: none;
  transition: all var(--transition-smooth);
  box-shadow: var(--rimc-shadow-xs);
  max-width: 48%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.topic-nav-btn:hover {
  color: var(--rimc-primary);
  border-color: var(--rimc-primary);
  background: var(--rimc-primary-soft);
  transform: translateY(-1px);
  box-shadow: var(--rimc-shadow-sm);
}
.topic-nav-btn.next {
  background: var(--rimc-primary);
  color: #fff;
  border-color: var(--rimc-primary);
  margin-left: auto;
  box-shadow: 0 3px 10px var(--rimc-primary-glow);
}
.topic-nav-btn.next:hover {
  background: var(--rimc-primary-dark);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 14px var(--rimc-primary-glow);
}

/* ==========================================================================
   FAQs — Polished accordion micro-interactions
   ========================================================================== */
.faq-accordion {
  margin: 1.15rem 0;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.faq-item {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--rimc-shadow-xs);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.faq-item[open] {
  border-color: var(--rimc-primary-glow);
  box-shadow: var(--rimc-shadow-sm);
}
.faq-question {
  padding: 0.85rem 1.15rem;
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--rimc-text);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  list-style: none;
  gap: 0.75rem;
  transition: background var(--transition-fast);
  -webkit-user-select: none;
  user-select: none;
}
.faq-question:hover {
  background: var(--rimc-bg-subtle);
}
.faq-question::-webkit-details-marker {
  display: none;
}
.faq-question:after {
  content: "\f078";
  font-family: "Font Awesome 6 Free";
  font-weight: 900;
  font-size: 0.68rem;
  color: var(--rimc-primary);
  transition: transform var(--transition-fast);
  flex-shrink: 0;
}
.faq-item[open] .faq-question:after {
  transform: rotate(180deg);
}
.faq-answer {
  padding: 0.75rem 1.15rem 1rem;
  font-size: 0.88rem;
  color: var(--rimc-text-secondary);
  line-height: 1.68;
  border-top: 1px solid var(--rimc-border-subtle);
  background: var(--rimc-bg-subtle);
}

/* ==========================================================================
   HUB TOPIC GRID & CARDS — Consistent elevation, smooth hover
   ========================================================================== */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}
.topic-card {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-lg);
  padding: 1.25rem 1.35rem;
  text-decoration: none;
  color: inherit;
  transition: all var(--transition-smooth);
  display: flex;
  flex-direction: column;
  box-shadow: var(--rimc-shadow-xs);
  position: relative;
}
.topic-card:hover {
  transform: translateY(-3px);
  border-color: var(--rimc-primary);
  box-shadow: var(--rimc-shadow-lg);
}
.topic-card-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 0.55rem;
}
.topic-number {
  font-size: 0.72rem;
  font-weight: 800;
  color: var(--rimc-primary);
  background: var(--rimc-primary-soft);
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--rimc-primary-glow);
}
.topic-card h3 {
  font-size: 1.04rem;
  font-weight: 800;
  color: var(--rimc-text);
  margin: 0 0 0.4rem;
  line-height: 1.35;
  letter-spacing: -0.01em;
}
.topic-card p {
  font-size: 0.84rem;
  color: var(--rimc-text-muted);
  margin: 0 0 0.85rem;
  line-height: 1.52;
  flex-grow: 1;
}
.topic-card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 0.75rem;
  border-top: 1px solid var(--rimc-border-subtle);
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--rimc-primary);
}
.topic-card-footer span:last-child i {
  transition: transform var(--transition-fast);
}
.topic-card:hover .topic-card-footer span:last-child i {
  transform: translateX(4px);
}

/* ==========================================================================
   DESCRIPTIVE RUBRIC GRID — Clear tiered cards
   ========================================================================== */
.rubric-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
  margin: 1.15rem 0;
}
.rubric-card {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-top: 3px solid var(--rimc-primary);
  border-radius: var(--radius-md);
  padding: 1.05rem;
  position: relative;
  min-width: 0;
  box-shadow: var(--rimc-shadow-xs);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}
.rubric-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--rimc-shadow-md);
}
.rubric-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}
.rubric-card-title {
  font-weight: 800;
  font-size: 0.9rem;
  color: var(--rimc-primary);
}

/* Trap & Trick Cards — Warning/Caution callouts */
.trap-card {
  background: rgba(225, 29, 72, 0.04);
  border: 1px solid rgba(225, 29, 72, 0.15);
  border-left: 3.5px solid #e11d48;
  border-radius: var(--radius-md);
  padding: 1rem 1.25rem;
  margin-bottom: 0.85rem;
  min-width: 0;
}
.trap-header {
  font-weight: 800;
  color: #be123c;
  font-size: 0.9rem;
  margin-bottom: 0.35rem;
  display: flex;
  align-items: center;
  gap: 0.45rem;
}
body.dark-mode .trap-card {
  background: rgba(225, 29, 72, 0.08);
  border-color: rgba(225, 29, 72, 0.22);
}
body.dark-mode .trap-header {
  color: #fb7185;
}
.trick-card {
  background: rgba(217, 119, 6, 0.04);
  border: 1px solid rgba(217, 119, 6, 0.18);
  border-left: 3.5px solid #d97706;
  border-radius: var(--radius-md);
  padding: 1rem 1.25rem;
  margin-bottom: 0.85rem;
  min-width: 0;
}
.trick-header {
  font-weight: 800;
  color: #b45309;
  font-size: 0.9rem;
  margin-bottom: 0.35rem;
  display: flex;
  align-items: center;
  gap: 0.45rem;
}
body.dark-mode .trick-card {
  background: rgba(217, 119, 6, 0.08);
  border-color: rgba(217, 119, 6, 0.22);
}
body.dark-mode .trick-header {
  color: #fbbf24;
}
.cadet-model-snippet {
  background: var(--rimc-bg-subtle);
  border: 1px dashed var(--rimc-border);
  border-radius: var(--radius-sm);
  padding: 0.6rem 0.85rem;
  margin-top: 0.5rem;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Courier New", monospace;
  font-size: 0.82rem;
  color: var(--rimc-text);
  line-height: 1.5;
}
.section-divider-banner {
  background: var(--rimc-header-bg);
  border: 1px solid var(--rimc-header-border);
  border-radius: var(--radius-md);
  padding: 0.75rem 1.25rem;
  margin: 1.5rem 0 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-weight: 800;
  font-size: 0.9rem;
  color: var(--rimc-text);
  box-shadow: var(--rimc-shadow-xs);
}

/* ==========================================================================
   MATHJAX OVERFLOW CONTAINMENT
   ========================================================================== */
mjx-container {
  max-width: 100% !important;
  overflow-x: auto !important;
  overflow-y: hidden !important;
  -webkit-overflow-scrolling: touch;
}
mjx-container[display="true"] {
  display: block !important;
  max-width: 100% !important;
  overflow-x: auto !important;
  overflow-y: hidden !important;
  margin: 0.5rem 0 !important;
  padding: 0.2rem 0 !important;
}

/* ==========================================================================
   VECTOR DIAGRAMS, SCHEMATICS & CHARTS — Refined card
   ========================================================================== */
.diagram-container {
  background: var(--rimc-bg-card);
  border: 1px solid var(--rimc-border);
  border-radius: var(--radius-lg);
  margin: 1.35rem 0;
  overflow: hidden;
  box-shadow: var(--rimc-shadow-sm);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.diagram-container:hover {
  border-color: var(--rimc-primary-glow);
  box-shadow: var(--rimc-shadow-md);
}
.diagram-header {
  background: var(--rimc-bg-subtle);
  border-bottom: 1px solid var(--rimc-border);
  padding: 0.65rem 1.15rem;
  font-size: 0.8rem;
  font-weight: 800;
  color: var(--rimc-primary);
  display: flex;
  align-items: center;
  gap: 0.45rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.diagram-header i {
  font-size: 0.75rem;
  opacity: 0.85;
}
.diagram-canvas {
  padding: 1.25rem 1.15rem;
  display: flex;
  justify-content: center;
  align-items: center;
  background: var(--rimc-bg-card);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.diagram-canvas svg {
  max-width: 100%;
  height: auto;
  display: block;
}
.diagram-caption {
  background: var(--rimc-bg-subtle);
  border-top: 1px solid var(--rimc-border);
  padding: 0.65rem 1.15rem;
  font-size: 0.82rem;
  color: var(--rimc-text-secondary);
  line-height: 1.58;
}
.diagram-caption strong {
  color: var(--rimc-primary);
}

/* Dark Mode SVG diagram background inversion */
body.dark-mode .diagram-canvas svg rect[fill="#f8fafc"],
body.dark-mode .diagram-canvas svg rect[fill="#f8fafb"] {
  fill: var(--rimc-bg-card);
}
body.dark-mode .diagram-canvas svg rect[fill="#ffffff"] {
  fill: var(--rimc-bg-subtle);
}
body.dark-mode .diagram-canvas svg text[fill="#1e293b"],
body.dark-mode .diagram-canvas svg text[fill="#334155"] {
  fill: var(--rimc-text);
}
body.dark-mode .diagram-canvas svg text[fill="#64748b"] {
  fill: var(--rimc-text-muted);
}
body.dark-mode .diagram-canvas svg line[stroke="#1e293b"] {
  stroke: var(--rimc-text-muted);
}
body.dark-mode .diagram-canvas svg rect[fill="#e2e8f0"] {
  fill: var(--rimc-border);
}
body.dark-mode .diagram-canvas svg rect[stroke="#e2e8f0"],
body.dark-mode .diagram-canvas svg line[stroke="#e2e8f0"] {
  stroke: var(--rimc-border);
}

/* ==========================================================================
   TYPOGRAPHY POLISH — Lists, links, inline code
   ========================================================================== */
.theory-block ul,
.theory-block ol {
  padding-left: 1.35rem;
  margin: 0.5rem 0;
}
.theory-block ul li,
.theory-block ol li {
  margin-bottom: 0.4rem;
  line-height: 1.65;
}
.theory-block ul li::marker {
  color: var(--rimc-primary);
}
.theory-block a {
  color: var(--rimc-primary);
  text-decoration-color: var(--rimc-primary-glow);
  text-underline-offset: 2px;
  transition: color var(--transition-fast);
}
.theory-block a:hover {
  color: var(--rimc-primary-light);
  text-decoration-thickness: 2px;
}

/* ==========================================================================
   RESPONSIVE BREAKPOINTS — Mobile pixel perfection
   ========================================================================== */
@media (max-width: 768px) {
  .rimc-hub-container,
  .topic-container,
  .subject-container {
    padding: 0 0.75rem 2rem;
    margin-top: 0.5rem;
  }
  .rimc-header,
  .topic-header,
  .subject-header {
    padding: 1.35rem 1rem 1.5rem;
    border-radius: var(--radius-lg);
  }
  .main-tabs-nav {
    display: flex;
    flex-wrap: nowrap;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    justify-content: flex-start;
    border-radius: var(--radius-lg);
    top: 60px;
    padding: 0.3rem 0.4rem;
    gap: 0.3rem;
    max-height: 50px;
    height: 48px;
  }
  .main-tabs-nav::-webkit-scrollbar {
    display: none;
  }
  .main-tabs-nav .tab-btn {
    font-size: 0.78rem;
    padding: 0.4rem 0.75rem;
    height: 36px;
    line-height: 1;
    white-space: nowrap !important;
    flex: 0 0 auto !important;
    width: auto !important;
    min-width: max-content !important;
  }
  .topic-grid {
    grid-template-columns: 1fr;
  }
  .rubric-grid {
    grid-template-columns: 1fr;
  }
  .theory-block,
  .card-premium,
  .practice-q-card {
    padding: 1.15rem 1rem;
  }
  .theory-block h2,
  .card-title {
    font-size: 1.1rem;
    gap: 0.45rem;
  }
  .theory-block h2 i,
  .card-title i {
    width: 28px;
    height: 28px;
    font-size: 0.82rem;
    border-radius: 7px;
  }
  .q-header {
    flex-direction: row;
    gap: 0.4rem;
  }
  .topic-nav-footer {
    flex-direction: column;
    align-items: stretch;
  }
  .topic-nav-btn {
    justify-content: center;
    width: 100%;
    max-width: 100%;
  }
  .topic-nav-btn.next {
    margin-left: 0;
  }
  .diagram-canvas {
    padding: 0.85rem 0.65rem;
  }
  .diagram-header,
  .diagram-caption {
    padding: 0.55rem 0.85rem;
    font-size: 0.76rem;
  }
  .formula-showcase {
    padding: 0.85rem;
  }
  .formula-card {
    padding: 0.75rem 0.95rem;
  }
  .faq-question {
    font-size: 0.85rem;
    padding: 0.75rem 1rem;
  }
  .faq-answer {
    padding: 0.65rem 1rem 0.85rem;
    font-size: 0.84rem;
  }
  .premium-table th {
    font-size: 0.72rem;
    padding: 0.6rem 0.75rem;
  }
  .premium-table td {
    font-size: 0.82rem;
    padding: 0.6rem 0.75rem;
  }
}

/* Small mobile (< 400px) additional tightening */
@media (max-width: 400px) {
  .rimc-header h1,
  .topic-header h1,
  .subject-header h1 {
    font-size: 1.32rem;
  }
  .rimc-header p,
  .topic-header p,
  .subject-header p {
    font-size: 0.84rem;
  }
  .breadcrumbs {
    font-size: 0.72rem;
    padding: 0.3rem 0.7rem;
    gap: 0.25rem;
  }
  .rimc-chip {
    font-size: 0.7rem;
    padding: 0.25rem 0.6rem;
  }
  .main-tabs-nav .tab-btn {
    font-size: 0.72rem;
    padding: 0.35rem 0.6rem;
    height: 34px;
  }
}

/* ==========================================================================
   PRINT STYLES — Clean reading mode
   ========================================================================== */
@media print {
  .main-tabs-nav,
  .breadcrumbs,
  .topic-nav-footer,
  .q-solution-toggle,
  #header-container,
  #footer-container {
    display: none !important;
  }
  .tab-panel {
    display: block !important;
  }
  .q-solution-body {
    display: block !important;
  }
  .theory-block,
  .card-premium,
  .practice-q-card {
    break-inside: avoid;
    box-shadow: none;
    border: 1px solid #ccc;
  }
  .diagram-container {
    break-inside: avoid;
  }
}