:root {
  --blue: #1a56db;
  --blue-dark: #1e40af;
  --blue-light: #dbeafe;
  --red: #dc2626;
  --red-dark: #b91c1c;
  --red-light: #fee2e2;
  --bg: #f8fafc;
  --surface: #ffffff;
  --text: #1e293b;
  --text-muted: #64748b;
  --border: #e2e8f0;
  --radius: 10px;
  --radius-sm: 6px;
  --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 40px rgba(0,0,0,0.1);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

.container { max-width: 1100px; margin: 0 auto; padding: 0 24px; }

.section-title {
  font-size: 2rem; font-weight: 800; text-align: center; margin-bottom: 12px;
}
.section-sub { text-align: center; color: var(--text-muted); max-width: 560px; margin: 0 auto 48px; font-size: 1.05rem; }
.text-gradient { background: linear-gradient(135deg, var(--blue), var(--red)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.text-red { color: var(--red); }
.text-blue { color: var(--blue); }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  font-weight: 600; border-radius: var(--radius-sm); cursor: pointer;
  transition: all 0.2s; text-decoration: none; border: none; font-size: 0.9rem;
}
.btn-primary { background: var(--blue); color: #fff; padding: 12px 28px; }
.btn-primary:hover { background: var(--blue-dark); transform: translateY(-1px); }
.btn-outline { background: transparent; border: 2px solid var(--border); color: var(--text); padding: 10px 24px; }
.btn-outline:hover { border-color: var(--blue); color: var(--blue); }
.btn-sm { padding: 8px 16px; font-size: 0.82rem; }
.btn-lg { padding: 16px 36px; font-size: 1rem; }
.btn-full { width: 100%; }

/* Nav */
.nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(255,255,255,0.92); backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: 1100px; margin: 0 auto; padding: 0 24px;
  display: flex; align-items: center; justify-content: space-between; height: 64px;
}
.logo { font-size: 1.3rem; font-weight: 800; text-decoration: none; }
.logo-tueri { color: var(--blue); }
.logo-prep { color: var(--red); }
.nav-links { display: flex; gap: 28px; }
.nav-links a { color: var(--text-muted); text-decoration: none; font-weight: 500; font-size: 0.9rem; transition: color 0.15s; }
.nav-links a:hover { color: var(--blue); }
.nav-actions { display: flex; gap: 10px; }
.menu-toggle { display: none; flex-direction: column; gap: 5px; background: none; border: none; cursor: pointer; padding: 4px; }
.menu-toggle span { display: block; width: 24px; height: 2px; background: var(--text); border-radius: 2px; transition: 0.2s; }

/* Hero */
.hero {
  min-height: 100vh; display: flex; align-items: center;
  padding: 100px 0 60px; position: relative; overflow: hidden;
}
.hero-bg {
  position: absolute; inset: 0;
  background: radial-gradient(ellipse 80% 60% at 50% 0%, var(--blue-light), transparent),
              radial-gradient(ellipse 60% 50% at 80% 80%, var(--red-light), transparent);
  opacity: 0.6;
}
.hero .container { display: grid; grid-template-columns: 1fr 1fr; gap: 60px; align-items: center; position: relative; }
.hero-badge {
  display: inline-block; background: var(--blue-light); color: var(--blue-dark);
  font-size: 0.8rem; font-weight: 600; padding: 6px 14px; border-radius: 20px; margin-bottom: 20px;
}
.hero-content h1 { font-size: 3rem; font-weight: 800; line-height: 1.15; margin-bottom: 20px; }
.hero-content p { font-size: 1.1rem; color: var(--text-muted); margin-bottom: 28px; max-width: 480px; line-height: 1.7; }
.hero-cta { display: flex; align-items: center; gap: 16px; margin-bottom: 40px; flex-wrap: wrap; }
.hero-credit { font-size: 0.85rem; color: var(--red); font-weight: 600; }
.hero-stats { display: flex; gap: 32px; }
.stat { text-align: center; }
.stat-num { display: block; font-size: 1.5rem; font-weight: 800; color: var(--blue); }
.stat span:last-child { font-size: 0.8rem; color: var(--text-muted); }

.hero-visual { display: flex; justify-content: center; }
.hero-mockup { display: flex; gap: 16px; align-items: flex-start; }
.mockup-screen {
  background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow-lg);
  width: 280px; overflow: hidden; border: 1px solid var(--border);
}
.mockup-header { padding: 10px 14px; background: #f1f5f9; display: flex; gap: 6px; }
.mockup-dot { width: 10px; height: 10px; border-radius: 50%; background: var(--border); }
.mockup-body { padding: 16px; }
.mockup-q { font-size: 0.78rem; font-weight: 600; margin-bottom: 10px; color: var(--text); }
.mockup-opt {
  font-size: 0.75rem; padding: 8px 10px; margin-bottom: 6px;
  background: #f8fafc; border-radius: 4px; border: 1px solid var(--border);
}
.mockup-opt.selected { border-color: var(--blue); background: var(--blue-light); color: var(--blue-dark); font-weight: 600; }

.mockup-omr {
  background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow-lg);
  padding: 12px; border: 1px solid var(--border); width: 130px;
}
.omr-title { font-size: 0.65rem; font-weight: 700; color: var(--text-muted); text-align: center; margin-bottom: 8px; text-transform: uppercase; }
.omr-row { display: flex; align-items: center; gap: 4px; margin-bottom: 4px; padding: 3px 4px; border-radius: 4px; }
.omr-row.active { background: var(--blue-light); }
.omr-row span { font-size: 0.6rem; font-weight: 600; color: var(--text-muted); width: 16px; }
.omr-row i {
  font-style: normal; font-size: 0.55rem; width: 20px; height: 20px;
  border-radius: 50%; border: 1.5px solid var(--border); display: inline-flex;
  align-items: center; justify-content: center; color: var(--text-muted);
}
.omr-row i.filled { background: var(--blue); border-color: var(--blue); color: #fff; }

/* Features */
.features { padding: 80px 0; }
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; margin-top: 48px; }
.feature-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 28px; transition: all 0.2s;
}
.feature-card:hover { box-shadow: var(--shadow-lg); border-color: var(--blue); transform: translateY(-2px); }
.feature-icon { font-size: 2rem; margin-bottom: 14px; }
.feature-card h3 { font-size: 1.05rem; font-weight: 700; margin-bottom: 8px; }
.feature-card p { font-size: 0.9rem; color: var(--text-muted); line-height: 1.6; }

/* How It Works */
.how-it-works { padding: 80px 0; background: var(--surface); }
.steps { display: flex; align-items: flex-start; justify-content: center; gap: 16px; margin-top: 48px; flex-wrap: wrap; }
.step { text-align: center; max-width: 200px; flex: 1; min-width: 180px; }
.step-num {
  width: 48px; height: 48px; border-radius: 50%;
  background: linear-gradient(135deg, var(--blue), var(--red));
  color: #fff; font-size: 1.2rem; font-weight: 800;
  display: inline-flex; align-items: center; justify-content: center; margin-bottom: 16px;
}
.step h3 { font-size: 1rem; font-weight: 700; margin-bottom: 8px; }
.step p { font-size: 0.85rem; color: var(--text-muted); line-height: 1.5; }
.step-arrow { font-size: 1.5rem; color: var(--border); margin-top: 12px; }

/* Pricing */
.pricing { padding: 80px 0; }
.pricing-cards { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; max-width: 700px; margin: 48px auto 0; }
.pricing-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 32px; text-align: center; position: relative;
}
.pricing-card.featured { border-color: var(--blue); box-shadow: var(--shadow-lg); }
.pricing-badge {
  position: absolute; top: -12px; left: 50%; transform: translateX(-50%);
  background: var(--blue); color: #fff; font-size: 0.75rem; font-weight: 700;
  padding: 4px 16px; border-radius: 20px;
}
.pricing-card h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 16px; }
.price { font-size: 2.5rem; font-weight: 800; color: var(--blue); margin-bottom: 20px; }
.price span { font-size: 0.9rem; font-weight: 500; color: var(--text-muted); display: block; }
.pricing-card ul { list-style: none; text-align: left; margin-bottom: 24px; }
.pricing-card li { font-size: 0.85rem; padding: 6px 0; color: var(--text-muted); }
.pricing-card li::before { content: ''; }

/* Subjects */
.subjects-showcase { padding: 60px 0; background: var(--surface); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.subject-tags { display: flex; flex-wrap: wrap; gap: 10px; justify-content: center; margin-top: 32px; }
.subject-tags span {
  padding: 8px 18px; background: var(--blue-light); color: var(--blue-dark);
  border-radius: 20px; font-size: 0.82rem; font-weight: 500;
}

/* About */
.about { padding: 80px 0; }
.about-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; align-items: start; }
.about-text h2 { text-align: left; margin-bottom: 20px; }
.about-text p { color: var(--text-muted); margin-bottom: 12px; line-height: 1.7; }
.about-values { display: grid; gap: 16px; }
.value-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; display: flex; gap: 14px; align-items: center;
}
.value-icon { font-size: 1.8rem; }
.value-card h4 { font-size: 0.95rem; font-weight: 700; margin-bottom: 2px; }
.value-card p { font-size: 0.82rem; color: var(--text-muted); }

/* CTA */
.cta-section {
  padding: 80px 0; text-align: center;
  background: linear-gradient(135deg, var(--blue-dark), var(--red-dark)); color: #fff;
}
.cta-section h2 { font-size: 2rem; font-weight: 800; margin-bottom: 12px; }
.cta-section p { font-size: 1rem; opacity: 0.85; max-width: 500px; margin: 0 auto 24px; }
.cta-section .btn { background: #fff; color: var(--blue-dark); }
.cta-section .btn:hover { background: var(--blue-light); }

/* Footer */
.footer-main { background: #0f172a; color: #cbd5e1; padding: 60px 0 30px; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; margin-bottom: 40px; }
.footer-brand p { margin-top: 12px; font-size: 0.85rem; line-height: 1.6; }
.footer-links h4, .footer-contact h4 { color: #fff; font-size: 0.9rem; font-weight: 600; margin-bottom: 14px; }
.footer-links a { display: block; color: #94a3b8; text-decoration: none; font-size: 0.85rem; margin-bottom: 8px; transition: color 0.15s; }
.footer-links a:hover { color: #fff; }
.footer-contact p { font-size: 0.85rem; margin-bottom: 8px; }
.footer-address { margin-top: 8px; font-size: 0.8rem; color: #64748b; }
.footer-bottom { border-top: 1px solid #1e293b; padding-top: 20px; text-align: center; font-size: 0.8rem; color: #64748b; }

@media (max-width: 768px) {
  .hero .container { grid-template-columns: 1fr; gap: 40px; }
  .hero-content h1 { font-size: 2rem; }
  .hero-stats { gap: 20px; flex-wrap: wrap; }
  .hero-visual { display: none; }
  .feature-grid { grid-template-columns: 1fr; }
  .pricing-cards { grid-template-columns: 1fr; }
  .about-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .steps { flex-direction: column; align-items: center; }
  .step-arrow { transform: rotate(90deg); margin: 8px 0; }
  .nav-links { display: none; }
  .nav-links.open {
    display: flex; flex-direction: column; position: absolute; top: 64px; left: 0; right: 0;
    background: var(--surface); border-bottom: 1px solid var(--border); padding: 16px 24px; gap: 12px;
  }
  .menu-toggle { display: flex; }
  .nav-actions .btn-sm { padding: 6px 12px; font-size: 0.78rem; }
}