:root {
  color-scheme: light;
  --bg: #f4f1ea;
  --paper: #fffdf8;
  --paper-strong: #ffffff;
  --text: #292722;
  --muted: #69655e;
  --line: #d9d3c7;
  --line-soft: #e9e4da;
  --accent: #315e66;
  --accent-strong: #23484f;
  --accent-soft: #e7f0ef;
  --note: #f0ede5;
  --shadow: 0 18px 50px rgba(56, 48, 35, 0.08);
  --radius: 18px;
  --reading-width: 46rem;
}

html[data-theme="dark"] {
  color-scheme: dark;
  --bg: #161816;
  --paper: #20231f;
  --paper-strong: #252924;
  --text: #ecebe5;
  --muted: #b8b5ab;
  --line: #3b413a;
  --line-soft: #30362f;
  --accent: #8fc4c7;
  --accent-strong: #b9e0e1;
  --accent-soft: #263b3a;
  --note: #292d28;
  --shadow: none;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

/* Keep in-page headings, citations, and reference notes clear of the sticky header. */
[id] { scroll-margin-top: 5.25rem; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Georgia, "Yu Mincho", "Hiragino Mincho ProN", "Noto Serif JP", serif;
  font-size: 18px;
  line-height: 1.82;
  text-rendering: optimizeLegibility;
}

body[lang="en"] { line-height: 1.72; }

a { color: var(--accent-strong); text-underline-offset: 0.16em; }
a:hover { text-decoration-thickness: 2px; }

.skip-link {
  position: fixed;
  top: 0.5rem;
  left: 0.5rem;
  z-index: 1000;
  padding: 0.55rem 0.8rem;
  background: var(--paper-strong);
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  transform: translateY(-160%);
}
.skip-link:focus { transform: translateY(0); }

.reading-progress {
  position: fixed;
  inset: 0 0 auto 0;
  height: 3px;
  z-index: 999;
  background: transparent;
}
.reading-progress span {
  display: block;
  height: 100%;
  width: 0;
  background: var(--accent);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: 1px solid color-mix(in srgb, var(--line) 80%, transparent);
  background: color-mix(in srgb, var(--bg) 90%, transparent);
  backdrop-filter: blur(14px);
}
.header-inner {
  max-width: 82rem;
  margin: 0 auto;
  min-height: 4rem;
  padding: 0 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.brand {
  display: inline-flex;
  align-items: baseline;
  gap: 0.65rem;
  color: var(--text);
  text-decoration: none;
  font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
.brand strong { font-size: 1rem; letter-spacing: 0.01em; }
.brand span { color: var(--muted); font-size: 0.76rem; }
.header-actions { display: flex; align-items: center; gap: 0.45rem; }
.header-button,
.lang-link,
.toc-toggle {
  appearance: none;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--paper);
  color: var(--text);
  padding: 0.46rem 0.78rem;
  font: 600 0.78rem/1 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  text-decoration: none;
  cursor: pointer;
}
.header-button:hover,
.lang-link:hover,
.toc-toggle:hover { background: var(--accent-soft); border-color: var(--accent); }

.header-button:focus-visible,
.lang-link:focus-visible,
.toc-toggle:focus-visible,
a:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 70%, transparent);
  outline-offset: 3px;
}

.hero {
  max-width: 82rem;
  margin: 0 auto;
  padding: 4.8rem 1.25rem 2.1rem;
}
.hero-inner {
  max-width: 60rem;
  margin-left: clamp(0rem, 6vw, 7rem);
}
.kicker {
  margin: 0 0 0.9rem;
  color: var(--accent-strong);
  font: 700 0.78rem/1.3 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}
h1, h2, h3 {
  font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Kaku Gothic ProN", sans-serif;
  line-height: 1.25;
  text-wrap: balance;
}
h1 {
  margin: 0;
  max-width: 14ch;
  font-size: clamp(2.65rem, 7vw, 5.8rem);
  letter-spacing: -0.055em;
}
.deck {
  max-width: 44rem;
  margin: 1.25rem 0 0;
  color: var(--muted);
  font-size: clamp(1.08rem, 2vw, 1.32rem);
  line-height: 1.65;
}
.meta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem 1rem;
  margin-top: 1.3rem;
  color: var(--muted);
  font: 0.78rem/1.5 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

.page-grid {
  max-width: 82rem;
  margin: 0 auto 5rem;
  padding: 0 1.25rem;
  display: grid;
  grid-template-columns: minmax(13rem, 17rem) minmax(0, var(--reading-width));
  gap: clamp(2rem, 5vw, 5rem);
  justify-content: center;
  align-items: start;
}

.toc {
  position: sticky;
  top: 5.3rem;
  max-height: calc(100vh - 6.5rem);
  overflow: auto;
  padding: 1rem 0.1rem 1rem 0;
  font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
.toc h2 {
  margin: 0 0 0.85rem;
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}
.toc ol { list-style: none; margin: 0; padding: 0; }
.toc li { margin: 0; }
.toc a {
  display: block;
  padding: 0.42rem 0.62rem;
  border-left: 2px solid transparent;
  border-radius: 0 0.5rem 0.5rem 0;
  color: var(--muted);
  font-size: 0.81rem;
  line-height: 1.35;
  text-decoration: none;
}
.toc a:hover,
.toc a[aria-current] {
  color: var(--accent-strong);
  background: var(--accent-soft);
  border-left-color: var(--accent);
}
.toc .toc-sub a { padding-left: 1.05rem; font-size: 0.76rem; }
.toc-toggle { display: none; margin-bottom: 0.75rem; }

.article-shell {
  min-width: 0;
  background: var(--paper);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}
.project-summary {
  padding: 1.4rem 1.6rem;
  border-bottom: 1px solid var(--line-soft);
  background: linear-gradient(135deg, var(--accent-soft), color-mix(in srgb, var(--paper) 65%, var(--accent-soft)));
}
.project-summary h2 {
  margin: 0 0 0.45rem;
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.project-summary p { margin: 0; font-size: 0.95rem; color: var(--muted); }

article { padding: clamp(1.35rem, 4vw, 3.6rem); }
article > p:first-of-type { font-size: 1.08em; }
article p { margin: 0 0 1.25em; }
article h2 {
  margin: 3.7rem 0 1.2rem;
  padding-top: 0.3rem;
  font-size: clamp(1.55rem, 3.2vw, 2.25rem);
  letter-spacing: -0.025em;
}
article h2:first-of-type { margin-top: 0.8rem; }
article h3 {
  margin: 2.5rem 0 0.9rem;
  font-size: clamp(1.15rem, 2vw, 1.38rem);
}
article strong { font-weight: 700; }
article em { font-style: italic; }

.ref {
  font: 700 0.68em/1 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  vertical-align: super;
  margin-left: 0.08em;
}
.ref a { text-decoration: none; }

.callout {
  margin: 1.8rem 0;
  padding: 1rem 1.15rem;
  border-left: 4px solid var(--accent);
  border-radius: 0.7rem;
  background: var(--accent-soft);
  color: var(--text);
}
.callout p:last-child { margin-bottom: 0; }

.references {
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--line);
}
.references h2 { margin-top: 0; }
.references ol { padding-left: 1.4rem; }
.references li {
  margin: 0 0 1.05rem;
  padding-left: 0.4rem;
  color: var(--muted);
  font-size: 0.87rem;
  line-height: 1.65;
}
.references li:target {
  background: var(--accent-soft);
  border-radius: 0.5rem;
  box-shadow: 0 0 0 0.35rem var(--accent-soft);
}
.backref { text-decoration: none; margin-right: 0.35rem; }
.source-note {
  margin-top: 1.6rem;
  padding: 1rem 1.1rem;
  border-radius: 0.7rem;
  background: var(--note);
  color: var(--muted);
  font: 0.82rem/1.65 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 2rem 1.25rem 3rem;
  color: var(--muted);
  font: 0.78rem/1.6 ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
.footer-inner {
  max-width: 70rem;
  margin: 0 auto;
  display: grid;
  grid-template-columns: auto minmax(18rem, 1fr) auto;
  align-items: start;
  gap: 0.75rem 1.5rem;
}
.license-note { max-width: 55rem; }
.footer-languages {
  display: flex;
  gap: 0.75rem;
  white-space: nowrap;
}
.footer-languages [aria-current="page"] {
  color: var(--text);
  font-weight: 650;
}

@media (max-width: 760px) {
  .footer-inner { grid-template-columns: 1fr; }
}

@media (max-width: 900px) {
  .hero { padding-top: 3.6rem; }
  .hero-inner { margin-left: 0; }
  .page-grid { grid-template-columns: minmax(0, var(--reading-width)); gap: 1rem; }
  .toc { position: static; max-height: none; padding: 0; }
  .toc-toggle { display: inline-flex; }
  .toc nav { display: block; padding: 0.4rem 0 0.8rem; }
  .js .toc nav { display: none; }
  .js .toc[data-open="true"] nav { display: block; }
  .article-shell { border-radius: 14px; }
}

@media (max-width: 600px) {
  body { font-size: 17px; }
  .brand span { display: none; }
  .header-inner { padding: 0 0.85rem; }
  .hero { padding: 2.8rem 1rem 1.6rem; }
  .page-grid { padding: 0 0.7rem; }
  article { padding: 1.25rem 1rem 2.2rem; }
  .project-summary { padding: 1.1rem 1rem; }
  .header-button, .lang-link { padding: 0.43rem 0.65rem; }
}


@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

@media print {
  :root { --bg: #fff; --paper: #fff; --text: #111; --muted: #333; --line: #aaa; }
  body { font-size: 11pt; background: #fff; }
  .site-header, .toc, .reading-progress, .site-footer, .project-summary { display: none !important; }
  .hero { padding: 0 0 1rem; }
  .hero-inner { margin: 0; }
  h1 { font-size: 30pt; }
  .page-grid { display: block; max-width: none; padding: 0; margin: 0; }
  .article-shell { border: 0; box-shadow: none; }
  article { padding: 0; }
  article h2, article h3 { break-after: avoid; }
  .references li { break-inside: avoid; }
  a { color: inherit; }
}