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

:root {
  --color-bg: #ffffff;
  --color-card-bg: #f8f9fa;
  --color-text: #1a1a2e;
  --color-text-secondary: #4a4a6a;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-border: #e2e4e9;
  --color-success: #059669;
  --color-warn: #d97706;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', Consolas, monospace;
  --max-width: 820px;
}

html { font-size: 16px; scroll-behavior: smooth; }
body { font-family: var(--font-sans); color: var(--color-text); background: var(--color-bg); line-height: 1.7; -webkit-font-smoothing: antialiased; }

/* Nav */
nav { border-bottom: 1px solid var(--color-border); position: sticky; top: 0; background: rgba(255,255,255,0.95); backdrop-filter: blur(8px); z-index: 100; }
.nav-inner { max-width: var(--max-width); margin: 0 auto; display: flex; justify-content: space-between; align-items: center; padding: 14px 24px; }
.nav-logo a { font-family: var(--font-mono); font-size: 0.95rem; font-weight: 700; color: var(--color-text); text-decoration: none; }
.nav-links { list-style: none; display: flex; gap: 20px; }
.nav-links a { color: var(--color-text-secondary); text-decoration: none; font-size: 0.85rem; transition: color 0.2s; }
.nav-links a:hover { color: var(--color-accent); }

/* Main */
main { max-width: var(--max-width); margin: 0 auto; padding: 0 24px; }

/* Hero */
.hero { text-align: center; padding: 48px 0 40px; border-bottom: 1px solid var(--color-border); }
.hero-badge { display: inline-block; background: var(--color-card-bg); border: 1px solid var(--color-border); color: var(--color-text-secondary); font-size: 0.75rem; font-weight: 600; padding: 4px 14px; border-radius: 100px; margin-bottom: 16px; letter-spacing: 0.04em; }
.hero h1 { font-size: 1.75rem; font-weight: 700; line-height: 1.3; margin-bottom: 12px; }
.subtitle { font-size: 1rem; color: var(--color-text-secondary); max-width: 640px; margin: 0 auto 24px; line-height: 1.6; }
.hero-stats { display: flex; justify-content: center; gap: 32px; flex-wrap: wrap; }
.stat { text-align: center; }
.stat-num { display: block; font-family: var(--font-mono); font-size: 1.25rem; font-weight: 700; color: var(--color-accent); }
.stat-label { display: block; font-size: 0.75rem; color: var(--color-text-secondary); margin-top: 2px; }

/* Sections */
.section { padding: 40px 0; border-bottom: 1px solid var(--color-border); }
.section:last-of-type { border-bottom: none; }
.section h2 { font-size: 1.3rem; font-weight: 700; margin-bottom: 16px; }
.section p { font-size: 0.95rem; color: var(--color-text-secondary); margin-bottom: 14px; line-height: 1.7; }
.section a { color: var(--color-accent); }

/* Callouts */
.callout { border-radius: 8px; padding: 14px 18px; font-size: 0.88rem; line-height: 1.6; margin: 16px 0; }
.callout.note { background: #eff6ff; border: 1px solid #bfdbfe; color: #1e40af; }
.callout.warn { background: #fffbeb; border: 1px solid #fcd34d; color: #92400e; }

/* Reasons (Module 2) */
.reason { margin-bottom: 24px; }
.reason h3 { font-size: 1rem; font-weight: 700; margin-bottom: 6px; }
.reason p { margin-bottom: 4px; }
.reason-note { font-size: 0.82rem !important; color: var(--color-warn) !important; font-style: italic; }

/* Steps (Module 3) */
.step { margin-bottom: 24px; }
.step h3 { font-size: 0.95rem; font-weight: 700; margin-bottom: 4px; color: var(--color-accent); }
.step code { background: var(--color-card-bg); border: 1px solid var(--color-border); border-radius: 4px; padding: 1px 6px; font-family: var(--font-mono); font-size: 0.82rem; color: var(--color-accent); }

/* Pricing table */
.pricing-table { width: 100%; border-collapse: collapse; margin: 14px 0; font-size: 0.88rem; }
.pricing-table th { text-align: left; padding: 10px 14px; font-weight: 600; font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.05em; color: var(--color-text-secondary); border-bottom: 2px solid var(--color-border); }
.pricing-table td { padding: 10px 14px; border-bottom: 1px solid var(--color-border); color: var(--color-text-secondary); }
.pricing-table td:first-child { color: var(--color-text); font-weight: 600; }

/* Features grid */
.features-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-bottom: 24px; }
.feature-card { background: var(--color-card-bg); border: 1px solid var(--color-border); border-radius: 8px; padding: 18px; }
.feature-card h4 { font-size: 0.9rem; font-weight: 700; margin-bottom: 4px; }
.feature-card p { font-size: 0.85rem; margin-bottom: 0; }

/* Limitations box */
.limitations-box { background: #fef2f2; border: 1px solid #fecaca; border-radius: 8px; padding: 18px 22px; }
.limitations-box h3 { font-size: 0.9rem; font-weight: 700; color: #991b1b; margin-bottom: 10px; }
.limitations-box ol { font-size: 0.85rem; color: #7f1d1d; line-height: 1.7; padding-left: 20px; }
.limitations-box li { margin-bottom: 6px; }

/* Use cases */
.use-case { margin-bottom: 20px; }
.use-case h3 { font-size: 0.95rem; font-weight: 700; margin-bottom: 4px; }

/* FAQ */
.faq-item { border-bottom: 1px solid var(--color-border); }
.faq-item:last-child { border-bottom: none; }
.faq-q { width: 100%; background: none; border: none; padding: 16px 0; font-size: 0.95rem; font-weight: 600; text-align: left; cursor: pointer; color: var(--color-text); display: flex; justify-content: space-between; align-items: center; gap: 12px; font-family: inherit; }
.faq-q:hover { color: var(--color-accent); }
.faq-q::after { content: '+'; font-size: 1.2rem; font-weight: 400; color: var(--color-text-secondary); flex-shrink: 0; transition: transform 0.2s; }
.faq-q.open::after { content: '\2212'; }
.faq-a { max-height: 0; overflow: hidden; transition: max-height 0.3s ease, padding 0.3s ease; font-size: 0.9rem; color: var(--color-text-secondary); line-height: 1.7; }
.faq-a.open { max-height: 500px; padding-bottom: 16px; }

/* Next steps */
.next-grid { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 14px; }
.next-card { display: block; background: var(--color-card-bg); border: 1px solid var(--color-border); border-radius: 8px; padding: 18px; text-decoration: none; color: var(--color-text); transition: border-color 0.2s; }
.next-card:hover { border-color: var(--color-accent); }
.next-card .next-arrow { display: block; color: var(--color-accent); font-size: 1.1rem; margin-bottom: 6px; }
.next-card strong { display: block; font-size: 0.9rem; margin-bottom: 4px; }
.next-card span { font-size: 0.82rem; color: var(--color-text-secondary); }

/* Footer */
footer { max-width: var(--max-width); margin: 0 auto; padding: 24px; text-align: center; border-top: 1px solid var(--color-border); }
footer p { font-size: 0.82rem; color: var(--color-text-secondary); }
footer a { color: var(--color-accent); }

/* Responsive */
@media (max-width: 640px) {
  .hero h1 { font-size: 1.35rem; }
  .hero-stats { gap: 18px; }
  .features-grid { grid-template-columns: 1fr; }
  .next-grid { grid-template-columns: 1fr; }
  .nav-links { gap: 12px; }
  .nav-links a { font-size: 0.78rem; }
  .pricing-table { font-size: 0.78rem; }
  .pricing-table th, .pricing-table td { padding: 8px 10px; }
}
@media (max-width: 480px) {
  .hero { padding: 32px 0; }
  .hero h1 { font-size: 1.2rem; }
  .section { padding: 28px 0; }
  .nav-inner { padding: 12px 16px; }
  main { padding: 0 16px; }
}