:root {
  /* Default: Clean Professional Light Theme */
  --bg-body: #f8fafc;
  --bg-surface: #ffffff;
  --bg-card: #ffffff;
  --bg-card-hover: #f1f5f9;
  --border-color: #e2e8f0;
  --border-subtle: #cbd5e1;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-tertiary: #64748b;

  --brand-gold: #d97706;
  --brand-gold-glow: rgba(217, 119, 6, 0.12);
  --brand-blue: #2563eb;
  --brand-blue-hover: #1d4ed8;
  --success: #059669;
  --danger: #dc2626;

  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-card: 0 10px 25px -5px rgba(15, 23, 42, 0.08), 0 8px 10px -6px rgba(15, 23, 42, 0.04);
  --shadow-lg: 0 20px 25px -5px rgba(15, 23, 42, 0.12), 0 8px 10px -6px rgba(15, 23, 42, 0.06);
  --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
  --bg-body: #070b14;
  --bg-surface: #0e1626;
  --bg-card: #131d31;
  --bg-card-hover: #1a2742;
  --border-color: #1e293b;
  --border-subtle: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-tertiary: #64748b;

  --brand-gold: #f59e0b;
  --brand-gold-glow: rgba(245, 158, 11, 0.15);
  --brand-blue: #3b82f6;
  --brand-blue-hover: #2563eb;

  --shadow-card: 0 10px 25px -5px rgba(0, 0, 0, 0.6);
  --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.7);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background-color: var(--bg-body);
  color: var(--text-primary);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.65;
  transition: background-color 0.3s ease, color 0.3s ease;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.container { max-width: 1240px; margin: 0 auto; padding: 0 24px; width: 100%; }

/* Navigation */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(12px);
  transition: background-color 0.3s ease;
}
.nav-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 74px;
}
.logo-anchor {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--text-primary);
}
.logo-text {
  font-size: 1.3rem;
  font-weight: 900;
  letter-spacing: -0.03em;
}
.logo-tag {
  font-size: 0.68rem;
  font-weight: 800;
  color: var(--brand-gold);
  background: var(--brand-gold-glow);
  padding: 3px 8px;
  border-radius: 4px;
  border: 1px solid rgba(217, 119, 6, 0.3);
  text-transform: uppercase;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 24px;
  list-style: none;
}
.nav-link {
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 0.92rem;
  font-weight: 600;
  transition: var(--transition);
}
.nav-link:hover, .nav-link.active { color: var(--brand-blue); }

.btn-theme {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  width: 40px;
  height: 40px;
  border-radius: 8px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}
.btn-theme:hover { background: var(--bg-card-hover); }

/* Buttons & Badges */
.btn-cta {
  padding: 10px 20px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 700;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  border: 1px solid transparent;
  transition: var(--transition);
}
.btn-cta-gold {
  background: linear-gradient(135deg, #b45309, #d97706);
  color: #ffffff;
  box-shadow: 0 4px 12px rgba(217, 119, 6, 0.25);
}
.btn-cta-gold:hover {
  background: linear-gradient(135deg, #d97706, #f59e0b);
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(217, 119, 6, 0.35);
}
.btn-cta-blue {
  background: var(--brand-blue);
  color: #ffffff;
}
.btn-cta-blue:hover {
  background: var(--brand-blue-hover);
  transform: translateY(-2px);
}
.btn-cta-ghost {
  border-color: var(--border-color);
  background: var(--bg-card);
  color: var(--text-primary);
}
.btn-cta-ghost:hover { background: var(--bg-card-hover); border-color: var(--border-subtle); }

/* Hero */
.hero {
  padding: 80px 0 60px;
  text-align: center;
  border-bottom: 1px solid var(--border-color);
  background: radial-gradient(circle at 50% 20%, var(--brand-gold-glow) 0%, transparent 65%);
}
.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--brand-gold-glow);
  border: 1px solid rgba(217, 119, 6, 0.3);
  color: var(--brand-gold);
  padding: 6px 14px;
  border-radius: 30px;
  font-size: 0.8rem;
  font-weight: 800;
  text-transform: uppercase;
  margin-bottom: 22px;
}
.hero h1 {
  font-size: clamp(2.2rem, 4.5vw, 3.6rem);
  font-weight: 900;
  letter-spacing: -0.03em;
  line-height: 1.18;
  margin-bottom: 18px;
}
.hero p {
  color: var(--text-secondary);
  font-size: 1.15rem;
  max-width: 720px;
  margin: 0 auto 34px;
}

/* Tab Filters */
.institute-tabs {
  display: flex;
  gap: 10px;
  overflow-x: auto;
  padding: 24px 0 16px;
  scrollbar-width: thin;
}
.tab-institute {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 9px 18px;
  border-radius: 30px;
  font-size: 0.88rem;
  font-weight: 700;
  white-space: nowrap;
  cursor: pointer;
  transition: var(--transition);
}
.tab-institute:hover { border-color: var(--brand-blue); color: var(--text-primary); }
.tab-institute.active {
  background: var(--brand-blue);
  color: #ffffff;
  border-color: var(--brand-blue);
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.25);
}

/* Grid Cards */
.grid-tests {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
  gap: 26px;
  margin: 30px 0 80px;
}
.card-test {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 14px;
  padding: 28px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  box-shadow: var(--shadow-card);
  transition: var(--transition);
}
.card-test:hover {
  transform: translateY(-5px);
  border-color: var(--brand-blue);
  box-shadow: var(--shadow-lg);
}
.badge-institute {
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  color: var(--brand-gold);
  background: var(--brand-gold-glow);
  padding: 4px 10px;
  border-radius: 6px;
}
.badge-status {
  font-size: 0.72rem;
  font-weight: 800;
  padding: 4px 10px;
  border-radius: 6px;
}
.status-free { background: rgba(5, 150, 105, 0.12); color: var(--success); border: 1px solid rgba(5, 150, 105, 0.3); }
.status-pro { background: rgba(220, 38, 38, 0.12); color: var(--danger); border: 1px solid rgba(220, 38, 38, 0.3); }

/* Pricing Section */
.pricing-section {
  padding: 90px 0;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-color);
  text-align: center;
}
.pricing-card {
  max-width: 520px;
  margin: 36px auto 0;
  background: var(--bg-card);
  border: 2px solid var(--border-color);
  border-radius: 20px;
  padding: 40px;
  box-shadow: var(--shadow-lg);
}
.pricing-price {
  font-size: 3.2rem;
  font-weight: 900;
  color: var(--brand-gold);
  margin: 16px 0;
}
.qr-container {
  width: 200px;
  height: 200px;
  background: #ffffff;
  border: 2px solid var(--border-color);
  border-radius: 12px;
  padding: 14px;
  margin: 24px auto;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* SEO Keyword Rich Section */
.seo-keyword-silo {
  padding: 60px 0;
  border-top: 1px solid var(--border-color);
  background: var(--bg-body);
}
.keyword-tags-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 18px;
}
.keyword-pill {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-tertiary);
  font-size: 0.75rem;
  padding: 5px 12px;
  border-radius: 20px;
  text-decoration: none;
  transition: var(--transition);
}
.keyword-pill:hover {
  border-color: var(--brand-blue);
  color: var(--brand-blue);
}

/* Executive Footer */
.site-footer {
  margin-top: auto;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-color);
  padding: 70px 0 30px;
  color: var(--text-secondary);
  font-size: 0.9rem;
}
.footer-grid {
  display: grid;
  grid-template-columns: 2.2fr 1fr 1fr 1.2fr;
  gap: 40px;
  margin-bottom: 50px;
}
.footer-col h5 {
  color: var(--text-primary);
  font-size: 0.98rem;
  font-weight: 800;
  margin-bottom: 20px;
  letter-spacing: -0.01em;
  position: relative;
}
.footer-col h5::after {
  content: "";
  position: absolute;
  bottom: -6px;
  left: 0;
  width: 24px;
  height: 2px;
  background: var(--brand-gold);
}
.footer-links { list-style: none; }
.footer-links li { margin-bottom: 12px; }
.footer-links a { color: var(--text-secondary); text-decoration: none; transition: var(--transition); }
.footer-links a:hover { color: var(--brand-blue); padding-left: 4px; }
.live-status {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--success);
  margin-top: 14px;
}
.live-status::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--success);
  box-shadow: 0 0 8px var(--success);
}
.copyright-area {
  border-top: 1px solid var(--border-color);
  padding-top: 30px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.82rem;
  color: var(--text-tertiary);
}

/* Bottom to Top Floating Button */
.back-to-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
  cursor: pointer;
  z-index: 999;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: all 0.3s ease;
}
.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top:hover {
  background: var(--brand-blue);
  color: #ffffff;
  border-color: var(--brand-blue);
  transform: translateY(-4px);
}

@media (max-width: 900px) {
  .footer-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 600px) {
  .footer-grid { grid-template-columns: 1fr; }
  .nav-links { display: none; }
}