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

:root {
  --bg: #000;
  --fg: #f5f5f7;
  --secondary: #86868b;
  --tertiary: #a1a1a6;
  --muted: #6e6e73;
  --border: rgba(255, 255, 255, 0.08);
  --accent: #2997ff;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #fbfbfd;
    --fg: #1d1d1f;
    --secondary: #6e6e73;
    --tertiary: #424245;
    --muted: #86868b;
    --border: rgba(0, 0, 0, 0.08);
    --accent: #0066cc;
  }
}

body {
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Helvetica Neue', sans-serif;
  -webkit-font-smoothing: antialiased;
  line-height: 1.7;
  transition: background 0.3s ease, color 0.3s ease;
}

nav {
  padding: 20px 24px;
}

nav a {
  color: var(--accent);
  text-decoration: none;
  font-size: 15px;
  transition: opacity 0.2s;
}

nav a:hover {
  opacity: 0.7;
}

main {
  max-width: 640px;
  margin: 0 auto;
  padding: 40px 24px 80px;
}

h1 {
  font-size: 36px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: 4px;
}

.subtitle {
  font-size: 15px;
  color: var(--secondary);
  margin-bottom: 40px;
}

h2 {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-top: 36px;
  margin-bottom: 12px;
}

p {
  font-size: 15px;
  color: var(--tertiary);
  line-height: 1.7;
  margin-bottom: 16px;
}

ol {
  color: var(--tertiary);
  font-size: 15px;
  line-height: 1.7;
  padding-left: 24px;
  margin-bottom: 16px;
}

ol li {
  margin-bottom: 8px;
}

ol ol {
  margin-top: 8px;
  margin-bottom: 8px;
}

.effective {
  margin-top: 32px;
  color: var(--muted);
  font-size: 13px;
}

footer {
  border-top: 1px solid var(--border);
  padding: 20px 24px;
  text-align: center;
  color: var(--muted);
  font-size: 12px;
}