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

:root {
  --primary: #4f46e5;
  --primary-dark: #3730a3;
  --primary-light: #ede9fe;
  --text: #111827;
  --text-muted: #6b7280;
  --bg: #ffffff;
  --bg-alt: #f9fafb;
  --border: #e5e7eb;
  --radius: 12px;
}

html {
  scroll-behavior: smooth;
}

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

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

/* HEADER */
header {
  position: sticky;
  top: 0;
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
}

header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 16px;
  padding-bottom: 16px;
}

.logo {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text);
}

.logo span {
  color: var(--primary);
}

nav {
  display: flex;
  align-items: center;
  gap: 24px;
}

nav a {
  text-decoration: none;
  color: var(--text-muted);
  font-size: 0.95rem;
  transition: color 0.2s;
}

nav a:hover {
  color: var(--text);
}

.btn-nav {
  background: var(--primary);
  color: #fff !important;
  padding: 8px 20px;
  border-radius: 8px;
  font-weight: 500;
  transition: background 0.2s !important;
}

.btn-nav:hover {
  background: var(--primary-dark) !important;
}

/* HERO */
.hero {
  padding: 80px 0 60px;
  overflow: hidden;
}

.hero .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.badge {
  display: inline-block;
  background: var(--primary-light);
  color: var(--primary);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 4px 12px;
  border-radius: 100px;
  margin-bottom: 20px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.hero-content h1 {
  font-size: 2.8rem;
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 20px;
}

.hero-content h1 span {
  color: var(--primary);
}

.hero-content p {
  color: var(--text-muted);
  font-size: 1.1rem;
  margin-bottom: 32px;
  max-width: 460px;
}

.cta-group {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
  text-decoration: none;
  padding: 12px 28px;
  border-radius: 8px;
  font-weight: 600;
  transition: background 0.2s;
}

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

.btn-secondary {
  color: var(--text);
  text-decoration: none;
  padding: 12px 28px;
  border-radius: 8px;
  border: 1px solid var(--border);
  font-weight: 500;
  transition: border-color 0.2s;
}

.btn-secondary:hover {
  border-color: var(--primary);
  color: var(--primary);
}

/* HERO VISUAL */
.hero-visual {
  position: relative;
  height: 400px;
}

.central-graphic {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.ring {
  border-radius: 50%;
  border: 1px solid var(--primary-light);
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.ring-1 { width: 120px; height: 120px; }
.ring-2 { width: 220px; height: 220px; opacity: 0.6; }
.ring-3 { width: 320px; height: 320px; opacity: 0.3; }

.center-dot {
  width: 48px;
  height: 48px;
  background: var(--primary);
  border-radius: 50%;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  box-shadow: 0 0 0 8px var(--primary-light);
}

.card-float {
  position: absolute;
  background: white;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 16px;
  display: flex;
  align-items: center;
  gap: 12px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.08);
  min-width: 200px;
}

.card-1 { top: 20px; left: 0; }
.card-2 { top: 50%; right: 0; transform: translateY(-50%); }
.card-3 { bottom: 20px; left: 20px; }

.avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  flex-shrink: 0;
}

.avatar.teacher { background: linear-gradient(135deg, #6366f1, #8b5cf6); }
.avatar.student  { background: linear-gradient(135deg, #10b981, #059669); }

.icon-check {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: #d1fae5;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.icon-check::after {
  content: '✓';
  color: #059669;
  font-weight: 700;
}

.card-text strong {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
}

.card-text span {
  font-size: 0.78rem;
  color: var(--text-muted);
}

/* FEATURES */
.features {
  padding: 80px 0;
  background: var(--bg-alt);
}

.features h2,
.roles h2 {
  text-align: center;
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 48px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 24px;
}

.feature-card {
  background: white;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: box-shadow 0.2s;
}

.feature-card:hover {
  box-shadow: 0 8px 30px rgba(79,70,229,0.1);
}

.feature-icon {
  font-size: 2rem;
  margin-bottom: 16px;
}

.feature-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.feature-card p {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* ROLES */
.roles {
  padding: 80px 0;
}

.roles-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  max-width: 700px;
  margin: 0 auto;
}

.role-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px;
}

.role-card.highlight {
  background: var(--primary);
  border-color: var(--primary);
  color: white;
}

.role-icon {
  font-size: 2.5rem;
  margin-bottom: 16px;
}

.role-card h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 16px;
}

.role-card ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.role-card ul li {
  font-size: 0.9rem;
  color: var(--text-muted);
  padding-left: 20px;
  position: relative;
}

.role-card ul li::before {
  content: '→';
  position: absolute;
  left: 0;
  color: var(--primary);
}

.role-card.highlight ul li {
  color: rgba(255,255,255,0.85);
}

.role-card.highlight ul li::before {
  color: rgba(255,255,255,0.7);
}

/* FOOTER */
footer {
  padding: 32px 0;
  border-top: 1px solid var(--border);
}

footer .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

footer p {
  font-size: 0.9rem;
  color: var(--text-muted);
}

footer a {
  color: var(--primary);
  text-decoration: none;
}

/* RESPONSIVE */
@media (max-width: 768px) {
  .hero .container {
    grid-template-columns: 1fr;
  }

  .hero-visual {
    display: none;
  }

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

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

  nav a:not(.btn-nav) {
    display: none;
  }
}