/* ============================================================
   MERIDIAN — layout.css
   Page geometry: header, hero + Seam A, section archetypes,
   demo module, Seam B bookend, responsive.
   ============================================================ */

/* ---- Header ---- */
.site-header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  height: var(--header-h);
  transition: background .25s ease-out, border-color .25s ease-out;
  backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
}
.site-header[data-theme="dark"] { background: rgba(17, 40, 63, .72); border-bottom: 1px solid transparent; }
.site-header[data-theme="light"] { background: rgba(250, 251, 252, .88); border-bottom: 1px solid var(--line-light); }
.nav { display: flex; align-items: center; gap: 32px; height: var(--header-h); }
.nav-logo { flex: none; display: flex; }
.nav-logo img { height: 30px; }
.site-header .logo-light, .site-header[data-theme="dark"] .logo-dark { display: block; }
.site-header .logo-dark, .site-header[data-theme="dark"] .logo-light { display: none; }
.nav-links { display: flex; align-items: center; gap: 28px; list-style: none; }
.nav-links a {
  font: 500 14px var(--font-text); color: var(--tx-mut);
  transition: color .18s ease-out; padding: 6px 0;
}
.nav-links a:hover { color: var(--tx-hi); }
.nav-spacer { flex: 1; }
.nav-cta { display: flex; align-items: center; gap: 12px; }
.nav-toggle {
  display: none; width: 44px; height: 44px; background: none; border: 0; cursor: pointer;
  flex-direction: column; align-items: center; justify-content: center; gap: 5px;
}
.nav-toggle span { width: 20px; height: 2px; background: var(--tx-hi); transition: transform .18s ease-out, opacity .18s ease-out; }
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* mobile sheet */
.mobile-menu {
  display: none; position: fixed; inset: var(--header-h) 0 0 0; z-index: 99;
  background: var(--bg); padding: 32px var(--gutter);
}
.mobile-menu.open { display: block; }
.mobile-menu ul { list-style: none; display: grid; gap: 4px; }
.mobile-menu a { display: block; padding: 16px 4px; font: 600 20px var(--font-display); color: var(--tx-hi); border-bottom: 1px solid var(--line); }
.mobile-menu .btn { margin-top: 24px; width: 100%; }

/* sticky mobile CTA bar */
.sticky-cta {
  display: none; position: fixed; left: 0; right: 0; bottom: 0; z-index: 90;
  padding: 10px var(--gutter) calc(10px + env(safe-area-inset-bottom));
  background: rgba(250, 251, 252, .92); backdrop-filter: blur(16px);
  border-top: 1px solid var(--line-light);
  transform: translateY(110%); transition: transform .25s ease-out;
}
.sticky-cta.show { transform: none; }
.sticky-cta .btn { width: 100%; }

/* ---- Hero + Seam A ---- */
.hero {
  position: relative;
  padding: calc(var(--header-h) + 88px) 0 0;
  border-bottom: 1px solid var(--signal-35);   /* the dawn horizon */
}
.hero-stack { max-width: 720px; margin: 0 auto; text-align: center; }
.hero-stack .eyebrow { justify-content: center; }
.hero-ctas { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; margin-top: 36px; }
.hero-micro { margin-top: 18px; font-size: 13px; color: var(--tx-mut); }
.hero .t-lede { margin-top: 24px; }

/* dot-row that fades toward the horizon */
.seam-dots {
  height: 2px; margin-top: 64px; margin-bottom: 38px;
  background: repeating-linear-gradient(90deg, var(--signal-35) 0 2px, transparent 2px 24px);
  mask-image: linear-gradient(90deg, transparent, #000 30% 70%, transparent);
  -webkit-mask-image: linear-gradient(90deg, transparent, #000 30% 70%, transparent);
}

/* the straddling frame */
.straddle {
  position: relative; z-index: 2;
  max-width: 1080px; margin: 0 auto calc(-1 * var(--straddle));
}
.after-straddle { padding-top: calc(var(--straddle) + 96px); }

/* live signal row overlaid on the hero frame */
.live-row {
  position: absolute; top: 56px; left: 20px; z-index: 3;
  display: inline-flex; align-items: center; gap: 10px;
  background: var(--paper-0); color: var(--ink-hi);
  border: 1px solid var(--line-light); border-radius: var(--r-el);
  padding: 10px 16px; font: 500 13px var(--font-text);
  box-shadow: 0 1px 3px rgba(17, 40, 63, .08);
}

/* ---- Section archetypes ---- */

/* editorial (problem) — left-set, no cards */
.editorial { max-width: 760px; }
.editorial .t-h2 { margin-bottom: 28px; }
.editorial .link-arrow { margin-top: 28px; }

/* engine — sticky left / chips right */
.engine-grid { display: grid; grid-template-columns: 5fr 7fr; gap: 64px; align-items: start; }
.engine-sticky { position: sticky; top: calc(var(--header-h) + 32px); }
.sig-cluster { display: grid; gap: 12px; }
.sig-cluster .row { display: flex; flex-wrap: wrap; gap: 12px; }
.sig-cluster .row:nth-child(2) { padding-left: 28px; }
.sig-cluster .row:nth-child(3) { padding-left: 56px; }
.sigchip {
  display: inline-flex; align-items: center; gap: 10px;
  border: 1px solid var(--line); border-radius: var(--r-dot);
  padding: 11px 18px; font: 500 15px var(--font-text); color: var(--tx-hi);
  background: var(--bg-raise); transition: border-color .18s ease-out;
}
.sigchip:hover { border-color: rgba(97, 189, 107, .45); }
.stat-line { display: flex; gap: 56px; flex-wrap: wrap; margin-top: 56px; }
.stat-line .stat b {
  display: block; font: 600 40px/1 var(--font-display); letter-spacing: -0.02em;
  color: var(--tx-hi); font-variant-numeric: tabular-nums;
}
.stat-line .stat span {
  display: flex; align-items: center; gap: 8px; margin-top: 10px;
  font: 500 13px/1.4 var(--font-mono); letter-spacing: .06em; color: var(--tx-mut);
  text-transform: uppercase;
}

/* chapters — alternating 7/5 */
.chapter { display: grid; grid-template-columns: 7fr 5fr; gap: 64px; align-items: center; }
.chapter + .chapter { margin-top: var(--sect-minor); }
.chapter:nth-child(even) .chapter-copy { order: 2; }
.chapter .index { display: block; margin-bottom: 14px; }
.chapter .t-h3 { font-size: 26px; margin-bottom: 12px; }
.chapter p { max-width: 520px; }
.chapter .link-arrow { margin-top: 20px; }

/* feature bullets (platform page) */
.dot-list { list-style: none; margin-top: 20px; display: grid; gap: 11px; }
.dot-list li { display: flex; gap: 12px; align-items: baseline; color: var(--tx-hi); font-size: 16px; }
.dot-list li .sig { top: -2px; }

/* channels row */
.channel-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; margin-top: 48px; }
.channel { border-top: 1px solid var(--line); padding-top: 20px; }
.channel h3 { font-size: 18px; margin: 12px 0 8px; display: flex; align-items: flex-start; gap: 10px; }
.channel p { font-size: 15px; }
.footnote { margin-top: 28px; font-size: 13px; color: var(--tx-mut); }
.footnote a { text-decoration: underline; text-underline-offset: 3px; }

.credits-eyebrow { margin-top: 56px; margin-bottom: 0; }
.stat-line--tight { margin-top: 24px; }

/* video proof */
.video-sect { text-align: center; }
.video-sect .eyebrow { justify-content: center; }
.video-sect .frame { max-width: 880px; margin: 48px auto 0; text-align: left; }
.video-caption { margin-top: 20px; font-size: 15px; color: var(--tx-mut); }

/* demo module — the one green surface */
.demo-panel {
  border: 1px solid var(--signal-35); border-radius: var(--r-card);
  background: var(--signal-08);
  display: grid; grid-template-columns: 6fr 6fr; gap: 56px;
  padding: 56px;
}
.demo-panel .t-h2 { margin-bottom: 18px; }
.demo-list { list-style: none; margin: 24px 0 32px; display: grid; gap: 14px; }
.demo-list li { display: flex; gap: 14px; align-items: baseline; color: var(--tx-hi); font-size: 16px; max-width: 480px; }
.demo-micro { margin-top: 14px; font-size: 13px; color: var(--tx-mut); }
.demo-panel .frame { align-self: stretch; }
.demo-panel .frame-body { background: var(--paper-0); min-height: 700px; }
.embed-fallback { display: flex; align-items: center; justify-content: center; min-height: 700px; padding: 32px; text-align: center; font-size: 15px; color: var(--tx-mut); }
.embed-fallback a { color: var(--tx-hi); text-decoration: underline; text-underline-offset: 3px; }

/* provenance ledger */
.ledger { border-bottom: 1px solid var(--line); margin-top: 48px; }
.ledger-row {
  display: grid; grid-template-columns: 240px 1fr; gap: 32px;
  border-top: 1px solid var(--line); padding: 24px 0; align-items: baseline;
}
.ledger-row .index { text-transform: uppercase; letter-spacing: .06em; }
.ledger-row p { font-size: 16px; max-width: 620px; color: var(--tx-hi); }
.ledger-row p .mut { color: var(--tx-mut); }

/* secondary offering tiles */
.tile-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 32px; margin-top: 48px; }
.tile { border-top: 1px solid var(--line); padding-top: 22px; }
.tile h3 { font-size: 20px; display: flex; align-items: flex-start; gap: 10px; margin-bottom: 10px; }
.tile h3 .sig, .channel h3 .sig { margin-top: 8px; }
.tile p { font-size: 15px; margin-bottom: 16px; }

.frame--crop .frame-body img { aspect-ratio: 16 / 9.6; object-fit: cover; object-position: top center; width: 100%; }

/* ---- Seam B / bookend ---- */
.bookend {
  border-top: 1px solid var(--signal-35);      /* the dusk horizon */
  background: linear-gradient(180deg, var(--navy-900), var(--navy-950));
  padding-top: var(--sect-major);
}
.bookend-cta { text-align: center; max-width: 720px; margin: 0 auto; }
.bookend-cta .eyebrow { justify-content: center; }
.bookend-cta .t-h2 { max-width: none; }
.bookend-cta .hero-ctas { margin-top: 32px; }
.bookend-rule { border: 0; border-top: 1px solid var(--line-dark); margin-top: 96px; }
.footer-grid {
  display: grid; grid-template-columns: repeat(5, 1fr); gap: 40px;
  padding: 56px 0 0;
}
.footer-grid h3 {
  font: 600 12px/1 var(--font-mono); letter-spacing: .08em; text-transform: uppercase;
  color: var(--dust-hi); margin-bottom: 18px;
}
.footer-grid ul { list-style: none; display: grid; gap: 10px; }
.footer-grid a, .footer-grid li { font-size: 14px; color: var(--dust-mut); }
.footer-grid a { display: inline-block; padding: 3px 0; }
.footer-small a { display: inline-block; padding: 4px 0; }
.footer-grid a:hover { color: var(--dust-hi); }
.footer-mark { margin: 56px 0 0; }
.footer-mark img { height: 34px; }
.footer-small {
  display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap;
  padding: 28px 0 36px; margin-top: 24px; border-top: 1px solid var(--line-dark);
  font-size: 13px; color: var(--dust-mut);
}
.footer-small a { color: var(--dust-mut); text-decoration: underline; text-underline-offset: 3px; }

/* ---- Surface variants (still the semantic system: paper-0 / paper-100 bands) ---- */
.sect-paper0[data-theme="light"] { background: var(--paper-0); }
.sect-tint[data-theme="light"] { background: var(--paper-100); }
.engine-body { max-width: 420px; margin-top: 20px; }

/* utility variants (replace banned inline styles) */
.chip-note[data-pos="br"] { bottom: -14px; right: 20px; }
.chip-note[data-pos="bl"] { bottom: -14px; left: 20px; }
.straddle--sm { max-width: 920px; }
.quickstart { max-width: 840px; }
.editorial--head { margin-bottom: 64px; }
.tile-row--2 { grid-template-columns: repeat(2, 1fr); max-width: 920px; }
.sect-lede { margin-top: 16px; max-width: 640px; }
.bookend-cta .sect-lede { margin-left: auto; margin-right: auto; }
.video-sect .t-h2 { margin: 0 auto; }
.faq { margin-top: 48px; }
.tile .index + h3 { margin-top: 12px; }
.video-caption a, .quickstart p a, .demo-micro a, .footnote a, .faq details p a { text-decoration: underline; text-underline-offset: 3px; color: var(--tx-hi); }
@media (max-width: 960px) { .tile-row--2 { grid-template-columns: 1fr; } }

/* nav primary label swap on small screens */
.lbl-short { display: none; }
@media (max-width: 720px) {
  .lbl-full { display: none; }
  .lbl-short { display: inline; }
}

/* ---- Sub-page hero (compact) ---- */
.hero--sub { text-align: center; }
.hero--sub .hero-stack { max-width: 760px; }

/* how-to procession */
.procession { max-width: 760px; margin: 0 auto; position: relative; padding-left: 40px; }
.procession::before {
  content: ""; position: absolute; left: 2px; top: 8px; bottom: 8px; width: 1px; background: var(--line);
}
.step-block { position: relative; padding: 0 0 var(--sect-minor); }
.step-block:last-child { padding-bottom: 0; }
.step-block > .sig { position: absolute; left: -40px; top: 7px; }
.step-block .index { display: block; margin-bottom: 10px; }
.step-block .t-h3 { margin-bottom: 10px; }
.step-block .frame { margin-top: 28px; }
.quickstart { margin-top: 48px; }
.quickstart ol { list-style: none; display: grid; gap: 18px; margin-top: 8px; }
.quickstart li { display: flex; gap: 14px; align-items: baseline; }
.quickstart li b { color: var(--tx-hi); font-weight: 600; }
.quickstart li p { font-size: 15px; margin-top: 2px; }

/* ---- Responsive ---- */
@media (max-width: 960px) {
  .nav-links, .nav-cta .btn-ghost { display: none; }
  .nav-toggle { display: flex; }
  .engine-grid, .chapter, .demo-panel { grid-template-columns: 1fr; gap: 40px; }
  .chapter:nth-child(even) .chapter-copy { order: 0; }
  .engine-sticky { position: static; }
  .channel-row, .tile-row { grid-template-columns: 1fr 1fr; gap: 28px; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .demo-panel { padding: 36px 28px; }
  .sig-cluster .row:nth-child(2), .sig-cluster .row:nth-child(3) { padding-left: 0; }
}
@media (max-width: 720px) {
  .sticky-cta { display: block; }
  body.menu-locked { overflow: hidden; }
  .channel-row, .tile-row { grid-template-columns: 1fr; }
  .live-row { top: 48px; left: 12px; padding: 8px 12px; font-size: 12px; }
  .chip-note { font-size: 12px; padding: 7px 11px; }
  .stat-line { gap: 36px; }
  .ledger-row { grid-template-columns: 1fr; gap: 8px; }
  .hero-ctas .btn { flex: 1 1 100%; }
  .demo-panel .frame { display: none; }
  .procession { padding-left: 28px; }
  .step-block > .sig { left: -28px; }
}