/* ============================================================
   AORVIS — Layout
   ============================================================ */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: clamp(1.25rem, 4vw, 3rem);
}

section { position: relative; }
.band { padding-block: clamp(4rem, 9vw, 8rem); }
.band--paper { background: var(--bg-alt); }
.band--ink { background: var(--ink); color: #fff; }
.band--ink h1, .band--ink h2, .band--ink h3 { color: #fff; }
.band--tight { padding-block: clamp(3rem, 6vw, 5rem); }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255,255,255,.82);
  backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--line);
  transition: transform .4s var(--ease), background .3s var(--ease);
}
.site-header.is-hidden { transform: translateY(-100%); }
.site-header__inner {
  display: flex; align-items: center; gap: 2rem;
  height: var(--header-h);
}
.brand img { width: 112px; height: auto; }
.nav { margin-left: auto; }
.nav__list { display: flex; gap: clamp(1rem, 2.5vw, 2.25rem); }
.nav__link {
  font-family: var(--font-mono);
  font-size: var(--t-sm);
  letter-spacing: .02em;
  color: var(--slate);
  padding-block: .4rem;
  position: relative;
}
.nav__link::after {
  content: ""; position: absolute; left: 0; bottom: -2px; height: 2px;
  width: 100%; background: var(--blue); transform: scaleX(0);
  transform-origin: left; transition: transform .35s var(--ease);
}
.nav__link:hover, .nav__link.is-active { color: var(--ink); }
.nav__link.is-active::after, .nav__link:hover::after { transform: scaleX(1); }

.site-header__actions { display: flex; align-items: center; gap: 1rem; }
.nav-toggle { display: none; width: 28px; height: 22px; position: relative; }
.nav-toggle span {
  position: absolute; left: 0; width: 100%; height: 2px; background: var(--ink);
  transition: transform .35s var(--ease), opacity .2s var(--ease);
}
.nav-toggle span:nth-child(1) { top: 4px; }
.nav-toggle span:nth-child(2) { bottom: 4px; }
.nav-toggle[aria-expanded="true"] span:nth-child(1) { top: 10px; transform: rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { bottom: 10px; transform: rotate(-45deg); }

.mobile-nav {
  border-bottom: 1px solid var(--line);
  background: #fff;
  padding: 1rem clamp(1.25rem, 4vw, 3rem) 1.5rem;
}
.mobile-nav ul { display: grid; gap: .25rem; }
.mobile-nav a {
  display: flex; justify-content: space-between; align-items: center;
  font-family: var(--font-display); font-size: var(--t-lg); color: var(--ink);
  padding: .7rem 0; border-bottom: 1px solid var(--line);
}
.mobile-nav a .mono { color: var(--blue); }

/* ---------- Responsive header: hamburger below 820px ---------- */
@media (max-width: 900px) {
  .nav { display: none; }                       /* hide inline desktop nav */
  .site-header__actions { margin-left: auto; }  /* push toggle to the right */
  .site-header__actions .btn { display: none; } /* CTA lives in the mobile menu */
  .nav-toggle { display: block; }               /* reveal hamburger */
}
@media (min-width: 901px) {
  .mobile-nav { display: none !important; }      /* never leak onto desktop */
}

/* ---------- The signature: depth-ruler section index ---------- */
/* A two-column layout where the left gutter carries a mono section code,
   a depth tick and a vertical rule — the page reads like a survey log. */
.indexed {
  display: grid;
  grid-template-columns: minmax(0,1fr);
  gap: clamp(2rem, 5vw, 4rem);
}
@media (min-width: 900px) {
  .indexed { grid-template-columns: 200px minmax(0,1fr); }
}
.indexed__rail {
  position: relative;
  border-top: 2px solid var(--ink);
  padding-top: 1rem;
}
.indexed__code {
  font-family: var(--font-mono); font-size: var(--t-sm);
  color: var(--blue); letter-spacing: .1em;
}
.indexed__depth {
  display: block; margin-top: .35rem;
  font-family: var(--font-mono); font-size: var(--t-xs);
  color: var(--muted); letter-spacing: .08em;
}

/* ---------- Generic grids ---------- */
.grid { display: grid; gap: 1px; background: var(--line); }
.grid--2 { grid-template-columns: repeat(2, 1fr); }
.grid--3 { grid-template-columns: repeat(3, 1fr); }
.grid--4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 900px) { .grid--3, .grid--4 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 600px) { .grid--2, .grid--3, .grid--4 { grid-template-columns: 1fr; } }

.cols { display: grid; gap: clamp(1.5rem, 4vw, 3rem); }
@media (min-width: 800px) { .cols--2 { grid-template-columns: 1fr 1fr; } .cols--7-5 { grid-template-columns: 7fr 5fr; } .cols--5-7 { grid-template-columns: 5fr 7fr; } }

.stack > * + * { margin-top: var(--s-5); }
.section-head { max-width: 56ch; margin-bottom: clamp(2.5rem, 5vw, 4rem); }
.section-head h2 { font-size: var(--t-2xl); margin-top: 1rem; }
.section-head .lead { margin-top: 1.25rem; }