:root {
  --bg: #f4f6f8;
  --surface: #ffffff;
  --text: #1f2933;
  --muted: #66737f;
  --line: #dfe5ea;
  --accent: #19448e;
  --accent-soft: #eaf0fa;
  --max: 1160px;
  --article: 920px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", "Yu Gothic UI", Meiryo, sans-serif;
  line-height: 1.75; overflow-wrap: anywhere;
}
a { color: var(--accent); text-decoration-thickness: .08em; text-underline-offset: .14em; }
a:hover { text-decoration-thickness: .14em; }
.site-header { background: #172a46; color: #fff; }
.header-inner { max-width: var(--max); margin: 0 auto; padding: 28px 24px 22px; }
.brand { color: #fff; text-decoration: none; font-size: clamp(1.7rem, 4vw, 2.5rem); font-weight: 750; letter-spacing: .02em; }
.tagline { margin: 3px 0 18px; color: #cad6e7; }
.nav { display: flex; flex-wrap: wrap; gap: 8px 18px; border-top: 1px solid rgba(255,255,255,.16); padding-top: 13px; }
.nav a { color: #fff; text-decoration: none; font-weight: 600; }
.nav a:hover { text-decoration: underline; }
.container { max-width: var(--max); margin: 0 auto; padding: 36px 24px 64px; }
.article-container { max-width: var(--article); }
.hero { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: clamp(24px,5vw,50px); margin-bottom: 28px; }
.hero h1 { margin: 0 0 8px; font-size: clamp(2rem,5vw,3.5rem); line-height: 1.15; }
.hero p { color: var(--muted); margin: 0; font-size: 1.05rem; }
.section { margin-top: 40px; }
.section-title { margin: 0 0 16px; font-size: 1.45rem; }
.grid { display: grid; grid-template-columns: repeat(3, minmax(0,1fr)); gap: 16px; }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 20px; }
.card h2, .card h3 { margin: 0 0 8px; line-height: 1.4; }
.card p { margin: 0; color: var(--muted); }
.card-link { display: block; color: inherit; text-decoration: none; height: 100%; }
.card-link:hover h2, .card-link:hover h3 { color: var(--accent); }
.article-list { list-style: none; padding: 0; margin: 0; display: grid; gap: 10px; }
.article-list li { background: var(--surface); border: 1px solid var(--line); border-radius: 10px; padding: 14px 16px; }
.article-list a { font-weight: 650; }
.meta { color: var(--muted); font-size: .9rem; margin-top: 5px; }
.article-header { margin-bottom: 28px; padding-bottom: 20px; border-bottom: 1px solid var(--line); }
.article-header h1 { font-size: clamp(1.8rem,4.5vw,2.7rem); line-height: 1.3; margin: 0 0 8px; }
.breadcrumb { font-size: .9rem; color: var(--muted); margin-bottom: 22px; }
.breadcrumb a { color: var(--muted); }
.article-body { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: clamp(20px,5vw,44px); }
.article-body > :first-child { margin-top: 0; }
.article-body h2 { margin-top: 2.1em; padding-bottom: .3em; border-bottom: 2px solid var(--accent-soft); line-height: 1.45; }
.article-body h3 { margin-top: 1.8em; line-height: 1.45; }
.article-body p { margin: 1.15em 0; }
.article-body img { display: block; max-width: 100%; height: auto; margin: 20px auto; border-radius: 4px; }
.article-body figure { margin: 22px 0; }
.article-body figure.center, .article-body .center { text-align: center; }
.article-body .center-image { margin-left: auto; margin-right: auto; }
.article-body hr { border: 0; border-top: 1px solid var(--line); margin: 34px 0; }
.article-body blockquote { margin: 1.5em 0; padding: .8em 1.2em; border-left: 4px solid var(--accent); background: var(--accent-soft); }
.article-body code { background: #eef1f4; padding: .15em .35em; border-radius: 4px; }
.table-scroll { overflow-x: auto; margin: 20px 0; }
table { border-collapse: collapse; min-width: 100%; background: #fff; }
th, td { border: 1px solid #ccd4db; padding: 7px 9px; vertical-align: top; }
th { background: #f0f3f7; text-align: left; }
.columns { display: flex; gap: 18px; align-items: flex-start; }
.column { flex: 1 1 0; min-width: 0; }
.toc { border: 1px solid var(--line); background: #f8fafc; border-radius: 10px; padding: 16px 20px; margin: 22px 0; }
.toc ul, .toc ol { margin: 8px 0; }
.external-link { padding: 10px 12px; background: #f8fafc; border-left: 3px solid var(--accent); }
.legacy-emphasis { font-size: 1.12em; }
.archive-group { margin-top: 34px; scroll-margin-top: 20px; }
.archive-year { margin: 22px 0 8px; color: var(--muted); font-size: 1rem; }
.notice { background: #fff8df; border: 1px solid #ecd993; border-radius: 10px; padding: 14px 16px; margin: 20px 0; }

/* Home preview: compact topic strip under the main navigation. */
.topic-strip {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 7px;
  margin-top: 14px;
}
.topic-label {
  color: #aebfd5;
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .06em;
  margin-right: 2px;
}
.topic-chip {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 3px 10px;
  border: 1px solid rgba(255,255,255,.2);
  border-radius: 999px;
  background: rgba(255,255,255,.06);
  color: #eef4fb;
  font-size: .82rem;
  line-height: 1.35;
}
.container > .section:first-child { margin-top: 0; }

.site-footer { border-top: 1px solid var(--line); background: #fff; }
.footer-inner { max-width: var(--max); margin: 0 auto; padding: 22px 24px; color: var(--muted); font-size: .9rem; }
@media (max-width: 800px) {
  .grid { grid-template-columns: 1fr; }
  .columns { display: block; }
  .header-inner, .container { padding-left: 18px; padding-right: 18px; }
  .nav { gap: 8px 14px; }
}