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

:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --secondary: #64748b;
  --background: #f8fafc;
  --surface: #ffffff;
  --text: #1e293b;
  --text-secondary: #64748b;
  --border: #e2e8f0;
  --success: #22c55e;
  --warning: #f59e0b;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans KR', sans-serif;
  background: var(--background);
  color: var(--text);
  line-height: 1.6;
}

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

/* Header */
.header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
}

.header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 700;
  font-size: 18px;
  color: var(--text);
}

.nav {
  display: flex;
  gap: 32px;
}

.nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}

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

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: 8px;
  font-weight: 600;
  text-decoration: none;
  transition: all 0.2s;
  cursor: pointer;
  border: none;
}

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

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

.btn-secondary {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
}

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

.btn-large {
  padding: 16px 32px;
  font-size: 18px;
}

/* Hero Section */
.hero {
  padding: 160px 0 80px;
  text-align: center;
  background: linear-gradient(180deg, var(--surface) 0%, var(--background) 100%);
}

.hero h1 {
  font-size: 48px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 24px;
}

.hero-desc {
  font-size: 20px;
  color: var(--text-secondary);
  margin-bottom: 40px;
}

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

/* Features Section */
.features {
  padding: 80px 0;
}

.features h2, .agents h2, .download h2, .user-types h2, .tutorial h2 {
  text-align: center;
  font-size: 36px;
  font-weight: 700;
  margin-bottom: 16px;
}

.section-desc {
  text-align: center;
  color: var(--text-secondary);
  font-size: 18px;
  margin-bottom: 48px;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.feature-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 32px 24px;
  text-align: center;
  transition: transform 0.2s, box-shadow 0.2s;
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 24px rgba(0,0,0,0.1);
}

.feature-icon {
  font-size: 48px;
  margin-bottom: 16px;
}

.feature-card h3 {
  font-size: 18px;
  margin-bottom: 12px;
}

.feature-card p {
  color: var(--text-secondary);
  font-size: 14px;
}

/* User Types Section */
.user-types {
  padding: 80px 0;
  background: var(--surface);
}

.user-type-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 32px;
  margin-top: 48px;
}

.user-type-card {
  background: var(--background);
  border-radius: 16px;
  padding: 40px;
  border: 2px solid var(--border);
  transition: border-color 0.2s;
}

.user-type-card:hover {
  border-color: var(--primary);
}

.user-type-header {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
}

.user-type-icon {
  width: 64px;
  height: 64px;
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 32px;
}

.user-type-card.k12 .user-type-icon {
  background: #fef3c7;
}

.user-type-card.university .user-type-icon {
  background: #dbeafe;
}

.user-type-header h3 {
  font-size: 24px;
}

.user-type-header p {
  color: var(--text-secondary);
  font-size: 14px;
}

.user-type-features {
  list-style: none;
}

.user-type-features li {
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: flex-start;
  gap: 12px;
}

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

.user-type-features .check {
  color: var(--success);
  font-weight: bold;
}

.standards-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 16px;
}

.standard-tag {
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 12px;
  color: var(--text-secondary);
}

/* Agents Section */
.agents {
  padding: 80px 0;
  background: var(--surface);
}

.agent-pipeline {
  display: flex;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 48px;
}

.agent-step {
  background: var(--background);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  min-width: 140px;
  text-align: center;
}

.agent-number {
  width: 32px;
  height: 32px;
  background: var(--primary);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  margin: 0 auto 12px;
}

.agent-info h4 {
  font-size: 14px;
  margin-bottom: 4px;
}

.agent-info p {
  font-size: 12px;
  color: var(--text-secondary);
}

.agent-arrow {
  color: var(--primary);
  font-size: 24px;
  font-weight: bold;
}

/* Tutorial Section */
.tutorial {
  padding: 80px 0;
}

.tutorial-steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 32px;
  margin-top: 48px;
}

.tutorial-step {
  text-align: center;
}

.step-number {
  width: 48px;
  height: 48px;
  background: var(--primary);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  font-weight: 700;
  margin: 0 auto 16px;
}

.step-image {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  height: 160px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
  font-size: 48px;
}

.tutorial-step h4 {
  margin-bottom: 8px;
}

.tutorial-step p {
  color: var(--text-secondary);
  font-size: 14px;
}

/* Example Section */
.examples {
  padding: 80px 0;
  background: var(--surface);
}

.example-tabs {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-bottom: 32px;
}

.example-tab {
  padding: 12px 24px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--background);
  cursor: pointer;
  font-weight: 500;
  transition: all 0.2s;
}

.example-tab.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.example-content {
  background: var(--background);
  border-radius: 16px;
  padding: 32px;
}

.example-card {
  display: none;
}

.example-card.active {
  display: block;
}

.example-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border);
}

.example-header h4 {
  font-size: 20px;
}

.example-meta {
  display: flex;
  gap: 16px;
  color: var(--text-secondary);
  font-size: 14px;
}

.example-preview {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.preview-section h5 {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 12px;
}

.preview-list {
  list-style: none;
}

.preview-list li {
  padding: 8px 12px;
  background: var(--surface);
  border-radius: 8px;
  margin-bottom: 8px;
  font-size: 14px;
}

/* Download Section */
.download {
  padding: 80px 0;
}

.download-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 24px;
  padding: 48px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 48px;
}

.download-info h3 {
  font-size: 24px;
  margin-bottom: 8px;
}

.download-info p {
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.download-info ul {
  list-style: none;
}

.download-info li {
  padding: 8px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.download-info li::before {
  content: "✓";
  color: var(--success);
  font-weight: bold;
}

.download-action {
  text-align: center;
}

.download-note {
  margin-top: 12px;
  font-size: 12px;
  color: var(--text-secondary);
}

/* Footer */
.footer {
  background: var(--text);
  color: white;
  padding: 48px 0 24px;
}

.footer-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  margin-bottom: 32px;
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
}

.footer-desc {
  color: #94a3b8;
}

.footer-links {
  display: flex;
  gap: 24px;
}

.footer-links a {
  color: #94a3b8;
  text-decoration: none;
  transition: color 0.2s;
}

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

.footer-bottom {
  text-align: center;
  padding-top: 24px;
  border-top: 1px solid #334155;
  color: #64748b;
  font-size: 14px;
}

/* Responsive */
@media (max-width: 1024px) {
  .feature-grid {
    grid-template-columns: repeat(2, 1fr);
  }

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

  .agent-pipeline {
    flex-direction: column;
  }

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

  .user-type-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  .hero h1 {
    font-size: 32px;
  }

  .hero-buttons {
    flex-direction: column;
  }

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

  .tutorial-steps {
    grid-template-columns: 1fr;
  }

  .download-card {
    flex-direction: column;
    text-align: center;
  }

  .example-preview {
    grid-template-columns: 1fr;
  }

  .nav {
    display: none;
  }
}