*, *::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; }