:root {
  --fg: #1f2933;
  --muted: #52606d;
  --bg: #ffffff;
  --line: #e4e7eb;
  --accent: #0f766e;
}
@media (prefers-color-scheme: dark) {
  :root {
    --fg: #e4e7eb;
    --muted: #9aa5b1;
    --bg: #12181f;
    --line: #2d3741;
    --accent: #2dd4bf;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, "Segoe UI", "Hiragino Sans",
    "Noto Sans JP", sans-serif;
  line-height: 1.7;
}
main { max-width: 760px; margin: 0 auto; padding: 32px 16px 64px; }
header, footer { max-width: 760px; margin: 0 auto; padding: 16px; }
header { border-bottom: 1px solid var(--line); }
header a.brand { font-weight: 700; font-size: 1.25rem; color: var(--fg);
  text-decoration: none; }
nav a { margin-right: 16px; }
footer { border-top: 1px solid var(--line); color: var(--muted);
  font-size: 0.9rem; }
a { color: var(--accent); }
h1 { font-size: 1.6rem; line-height: 1.3; }
h2 { font-size: 1.2rem; margin-top: 2em; }
.lang { border-top: 1px solid var(--line); margin-top: 48px; padding-top: 16px; }
.muted { color: var(--muted); }