:root {
  --bg: #ffffff;
  --surface: #f6f7f9;
  --text: #172b4d;
  --muted: #5e6c84;
  --accent: #0c66e4;
  --border: #dfe1e6;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1d2125;
    --surface: #22272b;
    --text: #dee4ea;
    --muted: #9fadbc;
    --accent: #579dff;
    --border: #38414a;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}
header, main, footer { max-width: 760px; margin: 0 auto; padding: 0 16px; }
header { display: flex; align-items: center; justify-content: space-between; padding-top: 24px; padding-bottom: 8px; }
header a.brand { font-weight: 700; font-size: 20px; color: var(--text); text-decoration: none; }
nav a { margin-left: 16px; color: var(--muted); text-decoration: none; }
nav a:hover { color: var(--accent); }
h1 { font-size: 32px; line-height: 1.25; margin: 32px 0 8px; }
h2 { font-size: 22px; margin: 36px 0 8px; }
h3 { font-size: 18px; margin: 24px 0 4px; }
p.lead { font-size: 18px; color: var(--muted); margin-top: 0; }
a { color: var(--accent); }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 16px 20px; margin: 16px 0; }
.card h3 { margin-top: 0; }
ul, ol { padding-left: 22px; }
li { margin: 4px 0; }
.muted { color: var(--muted); }
footer { border-top: 1px solid var(--border); margin-top: 48px; padding-top: 16px; padding-bottom: 32px; color: var(--muted); font-size: 14px; }