/* ============================================================
   LAYOUT — shell, header, navigation, footer, section frames
   ============================================================ */

.shell {
  width: 100%;
  max-width: var(--shell-max);
  margin-inline: auto;
  padding-inline: var(--shell-pad);
}

.section {
  position: relative;
  padding-block: var(--section-y);
}

/* Full-section colour inversion — the reference's signature move. */
.section-invert {
  background: var(--invert-bg);
  color: var(--invert-body);
  --ink: var(--invert-ink);
  --ink-body: var(--invert-body);
  --ink-muted: var(--invert-muted);
  --line: var(--invert-line);
  --line-strong: var(--invert-line);
  --accent-bright: var(--invert-accent);
  --accent-warm-text: var(--invert-warm);
  --surface: transparent;
  transition: background-color var(--dur-slow) var(--ease-out);
}
.section-alt { background: var(--bg-alt); }

/* No `ch` measure here on purpose. `ch` resolves against THIS element's
   font-size (~1rem), but the heading inside is up to 7.5rem — which would
   squeeze the display type into a ~230px column, one word per line.
   The measure belongs on the title itself, where `ch` matches its own size. */
.section-head { margin-bottom: var(--sp-10); max-width: none; }
.section-head-wide { max-width: none; }
.section-foot { margin-top: var(--sp-9); }

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background-color var(--dur-base) var(--ease-out),
              border-color var(--dur-base) var(--ease-out),
              backdrop-filter var(--dur-base) var(--ease-out);
}
.site-header.is-stuck {
  background: var(--header-bg);
  backdrop-filter: saturate(160%) blur(16px);
  -webkit-backdrop-filter: saturate(160%) blur(16px);
  border-bottom-color: var(--line);
}

.header-inner {
  height: var(--header-h);
  display: flex;
  align-items: center;
  gap: var(--sp-6);
}
/* Flex items default to min-width:auto and refuse to shrink below their
   content, which is how a header silently pushes itself off-screen. */
.header-inner > * { min-width: 0; }

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  margin-right: auto;
  min-height: 44px;
}
.brand-mark {
  font-size: var(--fs-sm);
  font-weight: 900;
  color: var(--ink);
  text-transform: uppercase;
  letter-spacing: var(--tracking-label);
  white-space: nowrap;
}
.brand-dot { width: 5px; height: 5px; border-radius: 50%; background: var(--accent-bright); }
.brand-sub {
  font-size: var(--fs-xs);
  color: var(--ink-muted);
  text-transform: uppercase;
  letter-spacing: var(--tracking-label);
  white-space: nowrap;
}
/* The role line is a nicety, not information the header needs. It only
   appears when there is genuinely room for it beside a six-item nav. */
@media (max-width: 1500px) { .brand-sub, .brand-dot { display: none; } }

.nav-list { display: flex; align-items: center; gap: 0.15rem; }

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: center;
  height: 42px;
  padding-inline: 0.7rem;
  font-size: var(--fs-xs);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-muted);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease-out);
}
.nav-link:hover { color: var(--ink); }
.nav-link::after {
  content: "";
  position: absolute;
  left: 0.7rem; right: 0.7rem; bottom: 8px;
  height: 1px;
  background: var(--accent-bright);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur-base) var(--ease-out);
}
.nav-link[aria-current="true"] { color: var(--ink); }
.nav-link[aria-current="true"]::after { transform: scaleX(1); }

@media (max-width: 900px) { .nav-desktop { display: none; } }

.header-actions { display: flex; align-items: center; gap: 0.5rem; }

/* Scoped selectors on purpose: `.icon-btn` sets `display` too, and at equal
   specificity whichever comes last would win. These must not depend on order. */
.header-actions .nav-toggle { display: none; }
@media (max-width: 900px) {
  .header-actions .nav-toggle { display: inline-grid; }
  .header-actions .header-cta { display: none; }
}

.icon-btn {
  display: inline-grid;
  place-items: center;
  width: 42px; height: 42px;
  border-radius: var(--r-sm);
  color: var(--ink-muted);
  border: 1px solid transparent;
  transition: color var(--dur-fast) var(--ease-out),
              background-color var(--dur-fast) var(--ease-out),
              border-color var(--dur-fast) var(--ease-out);
}
.icon-btn:hover { color: var(--ink); background: var(--ink-faint); border-color: var(--line); }
.icon-btn > .icon { grid-area: 1 / 1; transition: opacity var(--dur-base) var(--ease-out); }

[data-theme="light"] .icon-moon,
[data-theme="dark"] .icon-sun { opacity: 0; pointer-events: none; }

.nav-toggle .icon-close { opacity: 0; }
.nav-toggle[aria-expanded="true"] .icon-menu { opacity: 0; }
.nav-toggle[aria-expanded="true"] .icon-close { opacity: 1; }

.header-progress {
  position: absolute; left: 0; right: 0; bottom: -1px;
  height: 2px; overflow: hidden; pointer-events: none;
}
.header-progress span {
  display: block; height: 100%; width: 100%;
  background: var(--accent-bright);
  transform: scaleX(0);
  transform-origin: left;
}

/* ---------- Mobile drawer ---------- */
.nav-scrim {
  position: fixed; inset: 0;
  z-index: calc(var(--z-drawer) - 1);
  background: var(--scrim);
  opacity: 0;
  transition: opacity var(--dur-base) var(--ease-out);
}
.nav-scrim.is-open { opacity: 1; }

.nav-mobile {
  position: fixed;
  top: var(--header-h);
  left: 0; right: 0;
  z-index: var(--z-drawer);
  max-height: calc(100dvh - var(--header-h));
  overflow-y: auto;
  padding: var(--sp-6) var(--shell-pad) calc(var(--sp-8) + env(safe-area-inset-bottom));
  background: var(--bg-alt);
  border-bottom: 1px solid var(--line);
  box-shadow: var(--shadow-3);
  transform: translateY(-10px);
  opacity: 0;
  transition: opacity var(--dur-base) var(--ease-out),
              transform var(--dur-base) var(--ease-out);
}
.nav-mobile.is-open { transform: translateY(0); opacity: 1; }

.nav-mobile-list { display: grid; }
.nav-mobile-link {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--sp-4);
  min-height: 58px;
  padding: 0.7rem 0;
  border-bottom: 1px solid var(--line);
  font-family: var(--font-display);
  font-size: var(--fs-3xl);
  color: var(--ink);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease-out),
              padding-left var(--dur-base) var(--ease-out);
}
.nav-mobile-link:hover { color: var(--accent-bright); padding-left: 0.5rem; }
.nav-mobile-link[aria-current="true"] { color: var(--accent-bright); }
.nav-mobile-link .idx {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--ink-muted);
}
.nav-mobile-foot { margin-top: var(--sp-7); display: grid; gap: var(--sp-3); }

/* ---------- Footer ---------- */
.site-footer {
  position: relative;
  border-top: 1px solid var(--line);
  background: var(--bg);
  padding-block: var(--sp-10) calc(var(--sp-8) + env(safe-area-inset-bottom));
  overflow: hidden;
}

/* Oversized watermark type behind the footer — the reference's ticker. */
.footer-tickers {
  position: absolute;
  inset: 0;
  z-index: 0;
  display: flex;
  flex-direction: column;
  justify-content: space-around;
  opacity: 0.05;
  pointer-events: none;
  user-select: none;
  font-family: var(--font-display);
  font-size: clamp(3rem, 15vh, 9rem);
  line-height: 1;
  text-transform: uppercase;
  white-space: nowrap;
  color: var(--ink);
}
.footer-ticker-row { display: flex; }
.footer-ticker-row span { padding-inline: 0.4em; }

.footer-inner { position: relative; z-index: 1; display: grid; gap: var(--sp-9); }
.footer-top {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr);
  gap: var(--sp-8);
  align-items: start;
}
@media (max-width: 720px) { .footer-top { grid-template-columns: 1fr; } }

.footer-word {
  font-family: var(--font-display);
  font-size: var(--fs-3xl);
  color: var(--ink);
  line-height: 1.2;
  max-width: 22ch;
}
.footer-nav { display: flex; flex-wrap: wrap; gap: 0.25rem 1.5rem; }
.footer-nav a {
  font-size: var(--fs-xs);
  text-transform: uppercase;
  letter-spacing: var(--tracking-label);
  color: var(--ink-muted);
  text-decoration: none;
  min-height: 34px;
  display: inline-flex;
  align-items: center;
}
.footer-nav a:hover { color: var(--ink); }

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3) var(--sp-7);
  align-items: center;
  justify-content: space-between;
  padding-top: var(--sp-6);
  border-top: 1px solid var(--line);
  font-size: var(--fs-xs);
  color: var(--ink-muted);
}

/* ---------- Back to top ---------- */
.to-top {
  position: fixed;
  right: clamp(1rem, 2.5vw, 2.5rem);
  bottom: calc(clamp(1rem, 2.5vw, 2.5rem) + env(safe-area-inset-bottom));
  z-index: var(--z-sticky);
  display: grid;
  place-items: center;
  width: 48px; height: 48px;
  border-radius: 50%;
  background: var(--surface);
  color: var(--ink);
  border: 1px solid var(--line-strong);
  box-shadow: var(--shadow-2);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity var(--dur-base) var(--ease-out),
              transform var(--dur-base) var(--ease-out),
              visibility var(--dur-base),
              border-color var(--dur-fast) var(--ease-out);
}
.to-top.is-visible { opacity: 1; visibility: visible; transform: translateY(0); }
.to-top:hover { border-color: var(--accent-bright); color: var(--accent-bright); }
.to-top:active { transform: scale(0.94); }