:root { --fg:#1a1a1a; --bg:#fff; --muted:#666; --line:#e5e5e5; }
@media (prefers-color-scheme: dark) {
  :root { --fg:#e8e8e8; --bg:#111; --muted:#999; --line:#2a2a2a; }
}

* { box-sizing: border-box; }

body {
  margin: 0 auto;
  padding: 3rem 1.25rem;
  max-width: 42rem;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.75;
  font-family: -apple-system, "Segoe UI", "Microsoft YaHei", system-ui, sans-serif;
}

h1 { font-size: 1.75rem; margin: 0 0 .5rem; }
h2 { font-size: 1.1rem; margin: 0 0 .75rem; }
p, li { color: var(--muted); }
header { border-bottom: 1px solid var(--line); padding-bottom: 1.5rem; margin-bottom: 2rem; }
footer { border-top: 1px solid var(--line); padding-top: 1rem; margin-top: 3rem; font-size: .85rem; }