:root {
  --primary: #1a56db;
  --primary-dark: #1041b0;
  --accent: #2563eb;
  --light-bg: #f0f5ff;
  --dark: #111827;
  --text: #1f2937;
  --text-light: #6b7280;
  --white: #ffffff;
  --radius: 8px;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--text);
  line-height: 1.6;
  background: var(--white);
}

a {
  text-decoration: none;
  color: inherit;
}

.container {
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 12px 28px;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, box-shadow 0.2s;
  text-align: center;
}

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

.btn-primary:hover {
  background: var(--primary-dark);
  box-shadow: var(--shadow);
}

.btn-outline {
  background: transparent;
  color: var(--primary);
  box-shadow: inset 0 0 0 2px var(--primary);
}

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

.btn-sm {
  padding: 8px 20px;
  font-size: 0.9rem;
}

/* Navigation */
.navbar {
  position: sticky;
  top: 0;
  background: var(--dark);
  z-index: 100;
  padding: 16px 0;
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--white);
  letter-spacing: -0.5px;
}

.nav-links {
  display: flex;
  gap: 28px;
}

.nav-links a {
  color: #d1d5db;
  font-size: 0.95rem;
  transition: color 0.2s;
}

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

/* Hamburger (CSS-only) */
.nav-toggle {
  display: none;
}

.hamburger {
  display: none;
  cursor: pointer;
  flex-direction: column;
  gap: 5px;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--white);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}

.nav-toggle:checked ~ .nav-container .hamburger span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle:checked ~ .nav-container .hamburger span:nth-child(2) {
  opacity: 0;
}

.nav-toggle:checked ~ .nav-container .hamburger span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.nav-toggle:checked ~ .mobile-menu {
  display: flex;
}

/* Mobile Menu */
.mobile-menu {
  display: none;
  flex-direction: column;
  background: var(--dark);
  padding: 0 24px 16px;
}

.mobile-menu li a {
  display: block;
  padding: 12px 0;
  color: #d1d5db;
  font-size: 1rem;
  border-bottom: 1px solid #1f2937;
  transition: color 0.2s;
}

.mobile-menu li a:hover {
  color: var(--white);
}

.mobile-menu li:last-child a {
  border-bottom: none;
  display: inline-block;
  margin-top: 8px;
}

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--dark) 0%, #1e3a5f 50%, var(--primary) 100%);
  padding: 100px 0 120px;
  text-align: center;
}

.hero-content {
  max-width: 720px;
  margin: 0 auto;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 800;
  color: var(--white);
  line-height: 1.15;
  margin-bottom: 20px;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: #cbd5e1;
  line-height: 1.7;
  margin-bottom: 36px;
}

.hero-buttons {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.hero .btn-outline {
  color: var(--white);
  box-shadow: inset 0 0 0 2px var(--white);
}

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

/* Section Titles */
.section-title {
  font-size: 2rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 12px;
}

.section-subtitle {
  text-align: center;
  color: var(--text-light);
  font-size: 1.05rem;
  max-width: 560px;
  margin: 0 auto 48px;
}

/* Subjects */
.subjects {
  padding: 80px 0;
}

.subjects-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.subject-card {
  background: var(--white);
  border: 1px solid #e5e7eb;
  border-radius: var(--radius);
  padding: 32px 24px;
  text-align: center;
  transition: box-shadow 0.2s, transform 0.2s;
}

.subject-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.subject-icon {
  font-size: 2.5rem;
  display: block;
  margin-bottom: 16px;
}

.subject-card h3 {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.subject-card p {
  font-size: 0.92rem;
  color: var(--text-light);
  line-height: 1.5;
}

/* How It Works */
.how-it-works {
  padding: 80px 0;
  background: var(--light-bg);
}

.steps {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  gap: 16px;
}

.step {
  text-align: center;
  flex: 1;
  max-width: 280px;
}

.step-number {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--primary);
  color: var(--white);
  font-size: 1.4rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 20px;
}

.step h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.step p {
  font-size: 0.92rem;
  color: var(--text-light);
  line-height: 1.5;
}

.step-arrow {
  font-size: 1.8rem;
  color: var(--primary);
  margin-top: 14px;
}

/* Testimonials */
.testimonials {
  padding: 80px 0;
}

.testimonials-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.testimonial-card {
  background: var(--light-bg);
  border-radius: var(--radius);
  padding: 32px 28px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.testimonial-text {
  font-size: 0.97rem;
  line-height: 1.65;
  color: var(--text);
  margin-bottom: 24px;
  font-style: italic;
}

.testimonial-author {
  display: flex;
  align-items: center;
  gap: 12px;
}

.testimonial-avatar {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--primary);
  color: var(--white);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1rem;
}

.testimonial-author strong {
  display: block;
  font-weight: 600;
  font-size: 0.95rem;
}

.testimonial-author span {
  font-size: 0.85rem;
  color: var(--text-light);
}

/* Pricing */
.pricing {
  padding: 80px 0;
  background: var(--light-bg);
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  align-items: start;
}

.pricing-card {
  background: var(--white);
  border: 1px solid #e5e7eb;
  border-radius: var(--radius);
  padding: 36px 28px;
  text-align: center;
  transition: box-shadow 0.2s, transform 0.2s;
  position: relative;
}

.pricing-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.pricing-card.popular {
  border: 2px solid var(--primary);
  box-shadow: var(--shadow-lg);
  transform: scale(1.04);
}

.pricing-card.popular:hover {
  transform: scale(1.04) translateY(-4px);
}

.popular-badge {
  position: absolute;
  top: -14px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--primary);
  color: var(--white);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 4px 16px;
  border-radius: 20px;
}

.pricing-card h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 16px;
}

.price {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--primary);
  margin-bottom: 24px;
}

.price span {
  font-size: 0.95rem;
  font-weight: 400;
  color: var(--text-light);
}

.features {
  text-align: left;
  margin-bottom: 28px;
}

.features li {
  padding: 8px 0;
  font-size: 0.93rem;
  color: var(--text);
  border-bottom: 1px solid #f3f4f6;
}

.features li:last-child {
  border-bottom: none;
}

.pricing-card .btn {
  width: 100%;
  box-sizing: border-box;
}

/* Contact */
.contact {
  padding: 80px 0;
}

.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  align-items: start;
}

.contact-item {
  margin-bottom: 24px;
}

.contact-item h4 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 4px;
  color: var(--text);
}

.contact-item p {
  font-size: 0.95rem;
  color: var(--text-light);
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.contact-form input,
.contact-form textarea {
  padding: 12px 16px;
  border: 1px solid #d1d5db;
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-family: inherit;
  color: var(--text);
  outline: none;
  transition: border-color 0.2s;
}

.contact-form input:focus,
.contact-form textarea:focus {
  border-color: var(--primary);
}

.contact-form textarea {
  resize: vertical;
}

/* Footer */
.footer {
  background: var(--dark);
  color: #d1d5db;
  padding: 60px 0 0;
}

.footer-content {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 40px;
}

.footer-brand p {
  margin-top: 12px;
  font-size: 0.92rem;
  line-height: 1.5;
  color: #9ca3af;
}

.footer h4 {
  color: var(--white);
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 16px;
}

.footer-links ul {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  font-size: 0.92rem;
  color: #9ca3af;
  transition: color 0.2s;
}

.footer-links a:hover {
  color: var(--white);
}

.footer-contact p {
  font-size: 0.92rem;
  color: #9ca3af;
  line-height: 1.8;
}

.footer-bottom {
  margin-top: 48px;
  padding: 20px 0;
  border-top: 1px solid #1f2937;
  text-align: center;
  font-size: 0.85rem;
  color: #6b7280;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-links,
  .nav-cta {
    display: none;
  }

  .hamburger {
    display: flex;
  }

  .hero h1 {
    font-size: 2rem;
  }

  .subjects-grid,
  .testimonials-grid,
  .pricing-grid {
    grid-template-columns: 1fr;
  }

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

  .step-arrow {
    transform: rotate(90deg);
  }

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

  .footer-content {
    grid-template-columns: 1fr;
    gap: 32px;
  }
}