/* ===== CSS Variables ===== */
:root {
  --primary: #0f766e;
  --primary-dark: #0d5f58;
  --primary-light: #14b8a6;
  --accent: #f59e0b;
  --bg: #f8fafc;
  --bg-white: #ffffff;
  --text: #1e293b;
  --text-light: #64748b;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --radius: 12px;
  --radius-lg: 20px;
}

/* ===== Reset & Base ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

a {
  text-decoration: none;
  color: inherit;
  transition: color 0.3s;
}

ul {
  list-style: none;
}

img {
  max-width: 100%;
  height: auto;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== Navigation ===== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  transition: all 0.3s;
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
}

.logo-icon {
  font-size: 28px;
}

.logo-text {
  font-size: 22px;
  font-weight: 700;
  color: var(--text);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 36px;
}

.nav-links a {
  font-size: 15px;
  font-weight: 500;
  color: var(--text-light);
  transition: color 0.3s;
}

.nav-links a:hover {
  color: var(--primary);
}

.nav-btn {
  background: var(--primary);
  color: white !important;
  padding: 10px 24px;
  border-radius: 30px;
  font-weight: 600;
  transition: all 0.3s;
}

.nav-btn:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 8px;
  background: none;
  border: none;
  cursor: pointer;
}

.mobile-menu-btn span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  transition: all 0.3s;
}

.mobile-menu {
  display: none;
  position: fixed;
  top: 72px;
  left: 0;
  right: 0;
  background: white;
  padding: 20px 24px;
  border-bottom: 1px solid var(--border);
  z-index: 999;
  flex-direction: column;
  gap: 16px;
}

.mobile-menu.active {
  display: flex;
}

.mobile-menu a {
  font-size: 16px;
  font-weight: 500;
  color: var(--text);
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
}

.mobile-btn {
  background: var(--primary);
  color: white !important;
  padding: 14px 24px;
  border-radius: 30px;
  text-align: center;
  font-weight: 600;
  border: none !important;
  margin-top: 8px;
}

/* ===== Hero Section ===== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 120px 24px 80px;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, #f0fdfa 0%, #ecfdf5 50%, #f0f9ff 100%);
  z-index: -1;
}

.hero-bg::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 80%;
  height: 150%;
  background: radial-gradient(circle, rgba(15, 118, 110, 0.08) 0%, transparent 70%);
}

.hero-content {
  max-width: 800px;
  text-align: center;
}

.hero-title {
  font-size: clamp(36px, 6vw, 64px);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 24px;
  color: var(--text);
}

.highlight {
  color: var(--primary);
  position: relative;
}

.highlight::after {
  content: '';
  position: absolute;
  bottom: 5px;
  left: 0;
  right: 0;
  height: 8px;
  background: rgba(15, 118, 110, 0.2);
  z-index: -1;
  border-radius: 4px;
}

.hero-subtitle {
  font-size: clamp(16px, 2.5vw, 20px);
  color: var(--text-light);
  max-width: 600px;
  margin: 0 auto 40px;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 60px;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 32px;
  background: var(--primary);
  color: white;
  font-size: 16px;
  font-weight: 600;
  border-radius: 30px;
  transition: all 0.3s;
  border: 2px solid var(--primary);
}

.btn-primary:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-primary.large {
  padding: 18px 40px;
  font-size: 18px;
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 32px;
  background: white;
  color: var(--primary);
  font-size: 16px;
  font-weight: 600;
  border-radius: 30px;
  border: 2px solid var(--primary);
  transition: all 0.3s;
}

.btn-secondary:hover {
  background: var(--primary);
  color: white;
  transform: translateY(-2px);
}

.btn-outline {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 32px;
  background: transparent;
  color: white;
  font-size: 16px;
  font-weight: 600;
  border-radius: 30px;
  border: 2px solid white;
  transition: all 0.3s;
}

.btn-outline:hover {
  background: white;
  color: var(--primary);
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 60px;
  flex-wrap: wrap;
}

.stat {
  text-align: center;
}

.stat-number {
  display: block;
  font-size: 36px;
  font-weight: 800;
  color: var(--primary);
  line-height: 1.2;
}

.stat-label {
  font-size: 14px;
  color: var(--text-muted);
  margin-top: 4px;
}

/* ===== Section Styles ===== */
.section-header {
  text-align: center;
  margin-bottom: 60px;
}

.section-title {
  font-size: clamp(28px, 4vw, 42px);
  font-weight: 700;
  color: var(--text);
  margin-bottom: 16px;
}

.section-desc {
  font-size: 18px;
  color: var(--text-light);
  max-width: 600px;
  margin: 0 auto;
}

/* ===== Features Section ===== */
.features {
  padding: 100px 0;
  background: white;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 30px;
}

.feature-card {
  padding: 36px;
  background: var(--bg);
  border-radius: var(--radius-lg);
  transition: all 0.3s;
  border: 1px solid transparent;
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: rgba(15, 118, 110, 0.2);
}

.feature-icon {
  font-size: 48px;
  margin-bottom: 20px;
}

.feature-card h3 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text);
}

.feature-card p {
  font-size: 15px;
  color: var(--text-light);
  line-height: 1.7;
}

/* ===== Subjects Section ===== */
.subjects {
  padding: 100px 0;
  background: var(--bg);
}

.subject-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 24px;
}

.subject-card {
  padding: 40px 24px;
  background: white;
  border-radius: var(--radius-lg);
  text-align: center;
  transition: all 0.3s;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}

.subject-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  transition: height 0.3s;
}

.subject-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.subject-card:hover::before {
  height: 6px;
}

.subject-card.astronomy::before { background: linear-gradient(90deg, #0f766e, #155e75); }
.subject-card.physics::before { background: linear-gradient(90deg, #2563eb, #7c3aed); }
.subject-card.biology::before { background: linear-gradient(90deg, #15803d, #65a30d); }
.subject-card.chemistry::before { background: linear-gradient(90deg, #c2410c, #be123c); }
.subject-card.math::before { background: linear-gradient(90deg, #4338ca, #0891b2); }

.subject-icon {
  font-size: 56px;
  margin-bottom: 16px;
}

.subject-card h3 {
  font-size: 22px;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 8px;
}

.subject-card p {
  font-size: 14px;
  color: var(--text-light);
  margin-bottom: 12px;
}

.subject-count {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-muted);
}

/* ===== About Section ===== */
.about {
  padding: 100px 0;
  background: white;
}

.about-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 80px;
  align-items: center;
}

.about-text .section-title {
  text-align: left;
  margin-bottom: 24px;
}

.about-text p {
  font-size: 16px;
  color: var(--text-light);
  line-height: 1.8;
  margin-bottom: 20px;
}

.about-features {
  margin-top: 32px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.about-feature {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 16px;
  font-weight: 500;
}

.check {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: var(--primary);
  color: white;
  border-radius: 50%;
  font-size: 14px;
  font-weight: 700;
}

.about-visual {
  display: flex;
  justify-content: center;
}

.visual-card {
  background: linear-gradient(135deg, #f0fdfa 0%, #ecfdf5 100%);
  padding: 60px;
  border-radius: var(--radius-lg);
  text-align: center;
  width: 100%;
  max-width: 400px;
}

.visual-icon {
  font-size: 80px;
  margin-bottom: 20px;
}

.visual-card p {
  font-size: 18px;
  font-weight: 600;
  color: var(--text);
}

/* ===== CTA Section ===== */
.cta {
  padding: 100px 0;
  background: linear-gradient(135deg, var(--primary) 0%, #155e75 100%);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.cta::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -20%;
  width: 60%;
  height: 200%;
  background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 60%);
}

.cta h2 {
  font-size: clamp(28px, 4vw, 42px);
  font-weight: 700;
  color: white;
  margin-bottom: 16px;
}

.cta p {
  font-size: 18px;
  color: rgba(255, 255, 255, 0.9);
  margin-bottom: 40px;
}

.cta-buttons {
  display: flex;
  gap: 20px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Footer ===== */
.footer {
  background: var(--text);
  color: white;
  padding: 80px 0 0;
}

.footer-content {
  display: grid;
  grid-template-columns: 1.5fr 2fr;
  gap: 80px;
  margin-bottom: 60px;
}

.footer-brand .logo {
  margin-bottom: 16px;
}

.footer-brand .logo-text {
  color: white;
}

.footer-brand p {
  font-size: 15px;
  color: rgba(255, 255, 255, 0.7);
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 40px;
}

.footer-col h4 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 20px;
  color: white;
}

.footer-col a {
  display: block;
  font-size: 14px;
  color: rgba(255, 255, 255, 0.7);
  margin-bottom: 12px;
  transition: color 0.3s;
}

.footer-col a:hover {
  color: var(--primary-light);
}

.footer-bottom {
  padding: 24px 0;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  text-align: center;
}

.footer-bottom p {
  font-size: 14px;
  color: rgba(255, 255, 255, 0.5);
}

/* ===== Responsive ===== */
@media (max-width: 968px) {
  .nav-links {
    display: none;
  }

  .mobile-menu-btn {
    display: flex;
  }

  .about-content {
    grid-template-columns: 1fr;
    gap: 40px;
  }

  .about-text .section-title {
    text-align: center;
  }

  .footer-content {
    grid-template-columns: 1fr;
    gap: 40px;
  }
}

@media (max-width: 640px) {
  .hero {
    padding: 100px 20px 60px;
  }

  .hero-stats {
    gap: 40px;
  }

  .stat-number {
    font-size: 28px;
  }

  .feature-grid {
    grid-template-columns: 1fr;
  }

  .subject-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .footer-links {
    grid-template-columns: 1fr 1fr;
  }

  .hero-actions {
    flex-direction: column;
    align-items: center;
  }

  .btn-primary, .btn-secondary {
    width: 100%;
    max-width: 280px;
  }
}

/* ===== Animations ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.hero-content > * {
  animation: fadeInUp 0.8s ease-out;
}

.hero-content > *:nth-child(1) { animation-delay: 0.1s; }
.hero-content > *:nth-child(2) { animation-delay: 0.2s; }
.hero-content > *:nth-child(3) { animation-delay: 0.3s; }
.hero-content > *:nth-child(4) { animation-delay: 0.4s; }