:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --fg: #1c1c1e;
  --muted: #6b6b70;
  --rule: #e3e3e6;
  --accent: #2a6b6b;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #131315;
    --fg: #ececee;
    --muted: #9a9aa0;
    --rule: #2c2c30;
    --accent: #7fc8c8;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  padding: 0 1.25rem 5rem;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Noto Sans JP", "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.75;
  -webkit-text-size-adjust: 100%;
}

.wrap { max-width: 42rem; margin: 0 auto; }

header {
  padding: 2.5rem 0 1.25rem;
  border-bottom: 1px solid var(--rule);
  margin-bottom: 2rem;
}

.brand {
  font-size: 1.05rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  text-decoration: none;
  color: var(--fg);
}

nav { margin-top: 0.75rem; font-size: 0.9rem; }
nav a { color: var(--muted); text-decoration: none; margin-right: 1rem; }
nav a:hover { color: var(--accent); text-decoration: underline; }

.langbar { margin-top: 1rem; font-size: 0.85rem; }

.langbar button {
  font: inherit;
  font-size: 0.85rem;
  color: var(--muted);
  background: transparent;
  border: 1px solid var(--rule);
  border-radius: 999px;
  padding: 0.2rem 0.85rem;
  margin-right: 0.4rem;
  cursor: pointer;
}

.langbar button[aria-pressed="true"] {
  color: var(--bg);
  background: var(--accent);
  border-color: var(--accent);
}

h1 { font-size: 1.6rem; line-height: 1.35; margin: 0 0 0.5rem; }
h2 { font-size: 1.15rem; margin: 2.5rem 0 0.75rem; }
h3 { font-size: 1rem; margin: 1.75rem 0 0.5rem; }

.meta {
  color: var(--muted);
  font-size: 0.9rem;
  margin: 0 0 2rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--rule);
}

.meta div { margin: 0.15rem 0; }

p, ul { margin: 0.75rem 0; }
ul { padding-left: 1.25rem; }
li { margin: 0.4rem 0; }

a { color: var(--accent); }

.note {
  border-left: 3px solid var(--rule);
  padding: 0.25rem 0 0.25rem 1rem;
  color: var(--muted);
  margin: 1.5rem 0;
}

footer {
  margin-top: 4rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--rule);
  color: var(--muted);
  font-size: 0.85rem;
}

/* Language switching. Without JS every language block stays visible. */
main [data-lang], footer [data-lang] { display: block; }
body.lang-ja main [data-lang="en"],
body.lang-ja footer [data-lang="en"] { display: none; }
body.lang-en main [data-lang="ja"],
body.lang-en footer [data-lang="ja"] { display: none; }