:root {
  --bg: #ffffff;
  --surface: #f6f8fa;
  --text: #1f2328;
  --muted: #59636e;
  --primary: #1f6feb;
  --border: #d1d9e0;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1117;
    --surface: #161b22;
    --text: #e6edf3;
    --muted: #9198a1;
    --primary: #2f81f7;
    --border: #30363d;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.55 -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
}
main { max-width: 720px; margin: 0 auto; padding: 32px 16px 48px; }
h1 { font-size: 28px; line-height: 1.2; margin: 0 0 16px; }
h2 { font-size: 20px; margin: 28px 0 8px; }
p, li { color: var(--text); }
.muted { color: var(--muted); }
a { color: var(--primary); }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 16px; margin: 16px 0; }
.button {
  display: inline-block; background: var(--primary); color: #fff; text-decoration: none;
  padding: 12px 20px; border-radius: 10px; font-weight: 600; margin: 4px 8px 4px 0;
}
.button.secondary { background: transparent; color: var(--primary); border: 1.5px solid var(--primary); }
footer { margin-top: 40px; font-size: 13px; color: var(--muted); }
code { word-break: break-all; }