/* ═══════════════════════════════════════════════════════════════
   Three-column shell: book nav · content · page TOC
   ═══════════════════════════════════════════════════════════════ */

.shell {
  display: grid;
  grid-template-columns: var(--rail-left) minmax(0, 1fr) var(--rail-right);
  align-items: start;
  max-width: 1800px;
  margin: 0 auto;
}
.shell--notoc,
.shell--home { grid-template-columns: var(--rail-left) minmax(0, 1fr); }

/* ── Left rail: book navigation ──────────────────────────────── */
.booknav {
  position: sticky;
  top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  overscroll-behavior: contain;
  contain: paint;
  border-right: var(--border-w) solid var(--border);
  background: var(--muted);
  background-image:
    linear-gradient(to right, rgba(0,0,0,.03) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(0,0,0,.03) 1px, transparent 1px);
  background-size: 24px 24px;
}
.booknav__inner { padding: 24px 0 64px; }

.navgroup { border-bottom: var(--border-w) solid var(--border); }
.navgroup:last-child { border-bottom: 0; }

.navgroup__toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
  padding: 14px 20px;
  text-align: left;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .16em;
  text-transform: uppercase;
  transition: color .15s linear;
}
.navgroup__toggle:hover { color: var(--accent); }
.navgroup__num { color: var(--accent); font-family: var(--mono); }
.navgroup__label { flex: 1; }
.navgroup__chevron {
  width: 10px; height: 10px;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: rotate(-45deg);
  transition: transform .15s ease-out;
}
.navgroup.is-open .navgroup__chevron { transform: rotate(45deg); }

.navgroup__static {
  padding: 14px 20px 8px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: rgba(0,0,0,.5);
}

.navlist { list-style: none; margin: 0; padding: 0 0 12px; display: none; }
.navgroup.is-open .navlist { display: block; }

.navlink {
  display: flex;
  gap: 10px;
  padding: 7px 20px 7px 17px;
  border-left: var(--border-thick) solid transparent;
  font-size: 14px;
  line-height: 1.35;
  transition: color .15s linear, border-color .15s linear;
}
.navlink:hover { color: var(--accent); }
.navlink.is-active {
  border-left-color: var(--accent);
  font-weight: 700;
}
.navlink__num {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--accent);
  min-width: 18px;
  padding-top: 2px;
}
.navlink--part .navlink__title { font-style: italic; opacity: .75; }

.navsub {
  list-style: none;
  margin: 2px 0 8px;
  padding: 0 0 0 47px;
  border-left: var(--border-w) solid rgba(0,0,0,.15);
  margin-left: 17px;
}
.navsub__link {
  display: block;
  padding: 4px 0;
  font-size: 13px;
  line-height: 1.3;
  color: rgba(0,0,0,.65);
}
.navsub__link:hover { color: var(--accent); }

/* ── Center: content ─────────────────────────────────────────── */
.content {
  min-width: 0;
  padding: 48px 56px 96px;
}
.content--home { padding: 0 56px 96px; }

.crumbs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .16em;
  text-transform: uppercase;
  margin-bottom: 32px;
}
.crumbs a { border-bottom: 1px solid transparent; }
.crumbs a:hover { color: var(--accent); border-color: var(--accent); }
.crumbs__sep { color: var(--accent); }
.crumbs [aria-current] { color: rgba(0,0,0,.45); }

.pagehead {
  border-bottom: var(--border-thick) solid var(--border);
  padding-bottom: 28px;
  margin-bottom: 40px;
}
.pagehead__num {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 14px;
}
.pagehead__title {
  font-size: clamp(2.25rem, 5vw, 4.25rem);
  line-height: .95;
  letter-spacing: -0.035em;
  text-transform: uppercase;
}

/* inline TOC (tablet fallback) */
.toc-inline {
  display: none;
  border: var(--border-w) solid var(--border);
  margin-bottom: 40px;
}
.toc-inline summary {
  padding: 14px 20px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .18em;
  text-transform: uppercase;
  cursor: pointer;
}
.toc-inline[open] summary { border-bottom: var(--border-w) solid var(--border); }
.toc-inline ol { margin: 0; padding: 16px 20px 16px 40px; font-size: 14px; }

/* ── Pager ───────────────────────────────────────────────────── */
.pager {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-top: 72px;
}
.pager__item {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 24px;
  border: var(--border-w) solid var(--border);
  transition: background .15s linear, color .15s linear, border-color .15s linear;
}
.pager__item:only-child { grid-column: 1 / -1; }
.pager__item--next { text-align: right; }
.pager__item:hover { background: var(--fg); color: #fff; }
.pager__item--next:hover { background: var(--accent); border-color: var(--accent); }
.pager__dir {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--accent);
}
.pager__item:hover .pager__dir { color: #fff; }
.pager__title { font-weight: 700; font-size: 16px; line-height: 1.25; }

.updated {
  margin-top: 32px;
  font-size: 11px;
  font-weight: 500;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: rgba(0,0,0,.45);
}

/* ── Right rail: page TOC ────────────────────────────────────── */
.pagetoc {
  position: sticky;
  top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  overscroll-behavior: contain;
  contain: paint;
  border-left: var(--border-w) solid var(--border);
}
.pagetoc__inner { padding: 48px 24px 64px; }
.pagetoc__label {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .18em;
  text-transform: uppercase;
  padding-bottom: 12px;
  border-bottom: var(--border-w) solid var(--border);
  margin-bottom: 16px;
}
.pagetoc__list, .pagetoc__list ol { list-style: none; margin: 0; padding: 0; }
.pagetoc__list ol { padding-left: 14px; }
.pagetoc__list li { margin: 0; }
.pagetoc__list a {
  display: block;
  padding: 6px 0 6px 12px;
  border-left: var(--border-w) solid transparent;
  font-size: 13px;
  line-height: 1.35;
  color: rgba(0,0,0,.65);
  transition: color .15s linear, border-color .15s linear;
}
.pagetoc__list a:hover { color: var(--accent); }
.pagetoc__list a.is-current {
  color: var(--accent);
  border-left-color: var(--accent);
  font-weight: 700;
}

/* ── Home ────────────────────────────────────────────────────── */
.hero {
  padding: 72px 0 64px;
  border-bottom: var(--border-thick) solid var(--border);
}
.hero__label {
  font-size: 12px; font-weight: 700; letter-spacing: .2em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 24px;
}
.hero__title {
  font-size: clamp(3rem, 9vw, 7.5rem);
  line-height: .88;
  letter-spacing: -0.045em;
  text-transform: uppercase;
  margin-bottom: 40px;
}
.hero__meta {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 200px));
  gap: 24px;
  padding: 24px 0;
  border-top: var(--border-w) solid var(--border);
  border-bottom: var(--border-w) solid var(--border);
  margin-bottom: 32px;
}
.hero__meta-label {
  font-size: 10px; font-weight: 700; letter-spacing: .18em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 6px;
}
.hero__meta-value { font-weight: 700; font-size: 15px; }
.hero__lead {
  max-width: 62ch;
  font-size: 19px;
  line-height: 1.55;
  margin-bottom: 36px;
}

.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  border-bottom: var(--border-thick) solid var(--border);
}
.stat {
  padding: 32px 24px;
  border-right: var(--border-w) solid var(--border);
  transition: background .15s linear, color .15s linear;
}
.stat:last-child { border-right: 0; }
.stat:hover { background: var(--accent); color: #fff; }
.stat__num {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 900;
  line-height: 1;
  letter-spacing: -0.04em;
}
.stat__label {
  font-size: 11px; font-weight: 700; letter-spacing: .18em;
  text-transform: uppercase; margin-top: 8px;
}

.contents { padding: 64px 0 0; }
.contents__label {
  font-size: 12px; font-weight: 700; letter-spacing: .2em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 32px;
}
.contents__group { margin-bottom: 48px; }
.contents__group-title {
  font-size: 15px;
  letter-spacing: .1em;
  text-transform: uppercase;
  padding-bottom: 12px;
  border-bottom: var(--border-w) solid var(--border);
  margin-bottom: 4px;
}
.contents__list { list-style: none; margin: 0; padding: 0; }
.contents__item { margin: 0; border-bottom: 1px solid rgba(0,0,0,.12); }
.contents__item a {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding: 14px 8px;
  transition: background .15s linear, color .15s linear, padding .15s ease-out;
}
.contents__item a:hover { background: var(--fg); color: #fff; padding-left: 16px; }
.contents__num {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--accent);
  min-width: 28px;
}
.contents__item a:hover .contents__num { color: #fff; }
.contents__title { flex: 1; font-weight: 700; font-size: 16px; }
.contents__arrow { opacity: 0; transition: opacity .15s linear; }
.contents__item a:hover .contents__arrow { opacity: 1; }

/* ── Responsive ──────────────────────────────────────────────── */
@media (max-width: 1439px) {
  :root { --rail-left: 260px; --rail-right: 230px; }
  .content { padding: 40px 40px 80px; }
}

@media (max-width: 1279px) {
  .shell { grid-template-columns: var(--rail-left) minmax(0, 1fr); }
  .pagetoc { display: none; }
  .toc-inline { display: block; }
}

@media (max-width: 1023px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .topbar__burger { display: flex; }

  .booknav {
    position: fixed;
    top: var(--topbar-h);
    left: 0;
    width: min(85vw, 360px);
    height: calc(100vh - var(--topbar-h));
    z-index: 46;
    transform: translateX(-100%);
    transition: transform .2s ease-out;
    border-right: var(--border-thick) solid var(--border);
  }
  .booknav.is-open { transform: translateX(0); }
  .content, .content--home { padding: 32px 24px 80px; }
}

@media (max-width: 767px) {
  body { font-size: 16px; }
  .content, .content--home { padding: 24px 20px 64px; }
  .pager { grid-template-columns: 1fr; }
  .pager__item--next { text-align: left; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .stat:nth-child(2) { border-right: 0; }
  .stat:nth-child(1), .stat:nth-child(2) { border-bottom: var(--border-w) solid var(--border); }
  .hero { padding: 40px 0 40px; }
  .hero__meta { grid-template-columns: 1fr; gap: 16px; }
  .topbar__meta { display: none; }
}

/* ── Print ───────────────────────────────────────────────────── */
@media print {
  .topbar, .booknav, .pagetoc, .pager, .footer, .progress, .toc-inline { display: none !important; }
  .shell { display: block; }
  .content { padding: 0; }
  body { font-size: 11pt; }
}