:root {
  --bg: #f4f6f8;
  --surface: #ffffff;
  --text: #1b1f24;
  --muted: #5b6573;
  --accent: #00897b;
  --border: #e3e7ec;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0e1116;
    --surface: #161b22;
    --text: #e6edf3;
    --muted: #9aa5b1;
    --accent: #2ec4b6;
    --border: #2a313b;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Hiragino Sans", "Noto Sans JP", sans-serif;
  line-height: 1.7;
}
main { max-width: 760px; margin: 0 auto; padding: 32px 16px 64px; }
header { display: flex; justify-content: space-between; align-items: center; gap: 16px; flex-wrap: wrap; }
header .brand { font-weight: 700; font-size: 1.25rem; color: var(--text); text-decoration: none; }
nav a { color: var(--muted); margin-left: 16px; text-decoration: none; font-size: 0.95rem; }
nav a:hover { color: var(--accent); }
h1 { font-size: 1.9rem; line-height: 1.3; margin: 40px 0 8px; }
h2 { font-size: 1.25rem; margin: 40px 0 8px; }
h3 { font-size: 1.05rem; margin: 24px 0 4px; }
p.lead { color: var(--muted); font-size: 1.1rem; margin-top: 0; }
a { color: var(--accent); }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: 16px; padding: 4px 24px 16px; margin-top: 24px; }
ul { padding-left: 1.3em; }
li { margin: 4px 0; }
.updated { color: var(--muted); font-size: 0.9rem; }
footer { margin-top: 56px; color: var(--muted); font-size: 0.85rem; border-top: 1px solid var(--border); padding-top: 16px; }