:root {
  --bg: #f7f7f9;
  --card: #ffffff;
  --text: #1f2328;
  --sub: #59636e;
  --line: #d8dee4;
  --accent: #5865f2;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1e1f22;
    --card: #2b2d31;
    --text: #f2f3f5;
    --sub: #b5bac1;
    --line: #3f4147;
    --accent: #8891f2;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", "Hiragino Sans", "Yu Gothic UI", Meiryo, sans-serif;
  line-height: 1.75;
}
main {
  max-width: 760px;
  margin: 32px auto;
  padding: 32px 28px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
}
@media (max-width: 800px) {
  main { margin: 0; border-radius: 0; border-left: 0; border-right: 0; padding: 24px 16px; }
}
h1 { font-size: 1.6rem; margin: 0 0 4px; }
h2 { font-size: 1.15rem; margin: 28px 0 8px; padding-top: 8px; border-top: 1px solid var(--line); }
h3 { font-size: 1rem; margin: 16px 0 4px; }
p, li { margin: 6px 0; }
ul, ol { padding-left: 1.4em; }
a { color: var(--accent); }
.sub { color: var(--sub); font-size: 0.9rem; }
nav.lang { display: flex; gap: 12px; margin: 0 0 20px; font-size: 0.95rem; }
nav.lang a { text-decoration: none; padding: 2px 10px; border: 1px solid var(--line); border-radius: 999px; }
section + section { margin-top: 48px; padding-top: 8px; border-top: 3px double var(--line); }
footer { margin-top: 32px; color: var(--sub); font-size: 0.85rem; }