/* ============================================================
   Page shell: nav, section frame, footer, page-level grid.
   ============================================================ */

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

/* ---------- section frame -----------------------------------
   Rhythm is intentionally uneven: a hairline + index number
   opens each section, so the page reads like a stage itinerary. */

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

.section--tight {
  padding-block: calc(var(--s-section) * 0.6);
}

.section__head {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--s-5);
  align-items: start;
  padding-top: var(--s-5);
  border-top: var(--hair);
  margin-bottom: var(--s-7);
}

.section__index {
  font-family: var(--f-mono);
  font-size: var(--t-label);
  letter-spacing: var(--ls-label);
  color: var(--c-amber);
  padding-top: 0.55em;
}

.section__title {
  font-size: var(--t-d2);
}

.section__title em {
  font-style: normal;
  color: var(--c-ink-mute);
}

.section__intro {
  grid-column: 2;
  margin-top: var(--s-3);
}

@media (max-width: 40rem) {
  .section__head {
    grid-template-columns: 1fr;
    gap: var(--s-2);
  }
  .section__intro {
    grid-column: 1;
  }
}

/* ---------- nav ---------------------------------------------- */

.nav {
  position: fixed;
  inset-block-start: 0;
  inset-inline: 0;
  z-index: var(--z-nav);
  height: var(--nav-h);
  display: flex;
  align-items: center;
  transition:
    background var(--d-mid) var(--e-out),
    border-color var(--d-mid) var(--e-out),
    backdrop-filter var(--d-mid) var(--e-out);
  border-bottom: 1px solid transparent;
}

.nav[data-stuck="1"] {
  background: rgb(11 12 14 / 0.82);
  backdrop-filter: blur(14px) saturate(1.2);
  border-bottom-color: var(--c-edge-soft);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--s-5);
  width: 100%;
}

.nav__mark {
  display: flex;
  align-items: baseline;
  gap: 0.55rem;
  font-family: var(--f-display);
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.nav__mark b {
  font-weight: 700;
}

.nav__mark span {
  font-family: var(--f-mono);
  font-size: var(--t-label);
  letter-spacing: var(--ls-label);
  color: var(--c-amber);
}

.nav__links {
  display: flex;
  align-items: center;
  gap: clamp(0.9rem, 2vw, 2rem);
}

.nav__link {
  position: relative;
  font-family: var(--f-mono);
  font-size: var(--t-label);
  letter-spacing: var(--ls-label);
  text-transform: uppercase;
  color: var(--c-ink-dim);
  padding-block: var(--s-2);
  transition: color var(--d-fast) var(--e-out);
}

/* Underline grows from the left on hover, and stays lit for the
   section currently in view — the nav doubles as a progress read-out. */
.nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  height: 1px;
  width: 100%;
  background: var(--c-amber);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--d-mid) var(--e-out);
}

.nav__link:hover,
.nav__link[aria-current="true"] {
  color: var(--c-ink);
}

.nav__link:hover::after,
.nav__link[aria-current="true"]::after {
  transform: scaleX(1);
}

.nav__side {
  display: flex;
  align-items: center;
  gap: var(--s-4);
}

/* language switcher */
.lang {
  display: flex;
  align-items: center;
  border: var(--hair);
  border-radius: var(--r-sm);
  overflow: hidden;
}

.lang__btn {
  background: none;
  border: 0;
  cursor: pointer;
  padding: 0.4rem 0.6rem;
  font-family: var(--f-mono);
  font-size: var(--t-label);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--c-ink-mute);
  transition:
    color var(--d-fast) var(--e-out),
    background var(--d-fast) var(--e-out);
}

.lang__btn:hover {
  color: var(--c-ink);
}

.lang__btn[aria-pressed="true"] {
  background: var(--c-amber);
  color: var(--c-void);
}

/* scroll progress hairline pinned under the nav */
.nav__progress {
  position: absolute;
  left: 0;
  bottom: -1px;
  height: 2px;
  width: 100%;
  transform: scaleX(var(--progress, 0));
  transform-origin: left;
  background: linear-gradient(90deg, var(--c-amber-deep), var(--c-amber-hot));
}

/* burger — bars are absolutely centred on one point and pushed apart by
   transform, so the open state collapses them into a true X. Laying them
   out in normal flow leaves each bar in its own row and the "X" reads as
   a chevron instead. */
.burger {
  display: none;
  position: relative;
  width: 2.5rem;
  height: 2.5rem;
  border: var(--hair);
  border-radius: var(--r-sm);
  background: none;
  cursor: pointer;
  padding: 0;
}

.burger span:not(.visually-hidden) {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 1.1rem;
  height: 1px;
  margin-left: -0.55rem;
  background: var(--c-ink);
  transition: transform var(--d-mid) var(--e-out), opacity var(--d-fast);
}

.burger span:nth-child(1) {
  transform: translateY(-5px);
}
.burger span:nth-child(2) {
  transform: translateY(0);
}
.burger span:nth-child(3) {
  transform: translateY(5px);
}

.burger[aria-expanded="true"] span:nth-child(1) {
  transform: rotate(45deg);
}
.burger[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}
.burger[aria-expanded="true"] span:nth-child(3) {
  transform: rotate(-45deg);
}

@media (max-width: 62rem) {
  .burger {
    display: block;
  }

  .nav__links {
    position: fixed;
    inset: var(--nav-h) 0 auto 0;
    flex-direction: column;
    align-items: flex-start;
    gap: var(--s-4);
    padding: var(--s-6) var(--pad-x) var(--s-7);
    background: rgb(11 12 14 / 0.97);
    backdrop-filter: blur(18px);
    border-bottom: var(--hair);
    transform: translateY(-110%);
    transition: transform var(--d-mid) var(--e-in-out);
  }

  .nav__links[data-open="1"] {
    transform: translateY(0);
  }

  .nav__link {
    font-size: 1rem;
    letter-spacing: 0.12em;
  }
}

/* ---------- footer ------------------------------------------- */

.footer {
  border-top: var(--hair);
  background: var(--c-void);
  padding-block: var(--s-7) var(--s-6);
}

.footer__grid {
  display: grid;
  grid-template-columns: 1.4fr repeat(2, minmax(0, 1fr));
  gap: var(--s-6);
  align-items: start;
}

.footer__word {
  font-family: var(--f-display);
  font-size: clamp(3rem, 1rem + 9vw, 8rem);
  line-height: 0.82;
  text-transform: uppercase;
  color: var(--c-raise);
  letter-spacing: -0.02em;
  margin-block: var(--s-7) var(--s-5);
  user-select: none;
}

.footer__col h4 {
  font-size: var(--t-small);
  letter-spacing: var(--ls-label);
  color: var(--c-ink-mute);
  margin-bottom: var(--s-3);
}

.footer__col li + li {
  margin-top: var(--s-2);
}

.footer__col a {
  color: var(--c-ink-dim);
  transition: color var(--d-fast) var(--e-out);
}

.footer__col a:hover {
  color: var(--c-amber);
}

.footer__base {
  display: flex;
  flex-wrap: wrap;
  gap: var(--s-4);
  justify-content: space-between;
  align-items: center;
  margin-top: var(--s-7);
  padding-top: var(--s-4);
  border-top: var(--hair-soft);
  color: var(--c-ink-mute);
  font-family: var(--f-mono);
  font-size: var(--t-label);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

@media (max-width: 52rem) {
  .footer__grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 34rem) {
  .footer__grid {
    grid-template-columns: 1fr;
  }
}