:root {
  --bg: #ffffff;
  --fg: #1d1d1f;
  --muted: #6e6e73;
  --line: #e5e5ea;
  --accent: #0a84ff;
  --card: #f5f5f7;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --fg: #f5f5f7;
    --muted: #a1a1a6;
    --line: #2c2c2e;
    --accent: #409cff;
    --card: #1c1c1e;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Noto Sans JP", sans-serif;
  line-height: 1.8;
  -webkit-text-size-adjust: 100%;
}
main { max-width: 720px; margin: 0 auto; padding: 32px 16px 64px; }
header { margin-bottom: 32px; }
header a { color: var(--muted); text-decoration: none; font-size: 0.9rem; }
h1 { font-size: 1.6rem; line-height: 1.4; margin: 8px 0; }
h2 { font-size: 1.15rem; margin: 40px 0 8px; padding-top: 16px; border-top: 1px solid var(--line); }
h3 { font-size: 1rem; margin: 24px 0 4px; }
p, li { font-size: 0.97rem; }
a { color: var(--accent); }
.muted { color: var(--muted); font-size: 0.9rem; }
.card { background: var(--card); border-radius: 12px; padding: 16px 20px; margin: 16px 0; }
ul { padding-left: 1.3em; }
nav ul { list-style: none; padding: 0; }
nav li { margin: 8px 0; }
footer { margin-top: 56px; color: var(--muted); font-size: 0.85rem; }