@media (max-width: 1080px) {
  .opening { grid-template-columns: 1fr; min-height: auto; }
  .opening-copy { min-height: 640px; }
  .live-model { min-height: 680px; border-top: 1px solid var(--ink); border-left: 0; }
  .section-heading, .composition-field header { grid-template-columns: 0.4fr 1.6fr; }
  .section-heading > p:last-child, .composition-field header > p:last-child { grid-column: 2; }
  .route-list li { grid-template-columns: 54px minmax(160px, 0.65fr) minmax(260px, 1.35fr); }
  .route-state { grid-column: 3; justify-self: start; }
  .pricing { grid-template-columns: 0.55fr 1fr; }
  .purchase-panel { grid-column: 2; width: min(100%, 520px); }
}

@media (max-width: 840px) {
  :root { --page: calc(100% - 28px); --section-space: 104px; }
  .masthead { min-height: 72px; }
  .page-grid { display: block; }
  .provenance-rail {
    position: sticky;
    z-index: 9;
    top: 0;
    display: flex;
    align-items: center;
    width: 100%;
    height: 52px;
    padding: 0;
    border-right: 0;
    border-bottom: 1px solid var(--ink);
    background: var(--paper);
  }
  .provenance-rail::before { top: 25px; right: 0; bottom: auto; left: 0; width: 100%; height: 1px; }
  .rail-title { display: none; }
  .rail-nav { position: relative; z-index: 1; display: flex; flex: 1; justify-content: space-between; gap: 4px; margin: 0; }
  .rail-nav a { grid-template-columns: 28px auto; min-width: 72px; padding-inline: 7px; background: var(--paper); }
  .rail-nav a::before { left: 4px; }
  .ledger { border-left: 1px solid var(--ink); }
  .ledger-section { scroll-margin-top: 76px; }
  .section-heading, .mechanism-heading, .composition-field header { grid-template-columns: 1fr; }
  .section-heading > p:last-child, .composition-field header > p:last-child { grid-column: auto; max-width: 42em; }
  .section-heading h2, .composition-field h2 { margin-top: 30px; }
  .section-heading > p:last-child, .composition-field header > p:last-child { margin-top: 22px; }
  .route-list li { grid-template-columns: 54px 1fr; }
  .route-list h3, .route-list p, .route-state { grid-column: 2; }
  .route-state { justify-self: start; }
  .assembly > div { grid-template-columns: 66px 1fr; }
  .assembly dl, .assembly-format pre, .assembly-output .budget { grid-column: 2; }
  .privacy { grid-template-columns: 1fr; min-height: 680px; }
  .privacy-register { width: min(100%, 540px); }
  .pricing { grid-template-columns: 0.55fr 1fr; }
  .price-copy { grid-column: 2; }
  .purchase-panel { grid-column: 2; }
}

@media (max-width: 620px) {
  :root { --page: calc(100% - 20px); --section-space: 84px; }
  body { font-size: 16px; }
  .masthead { grid-template-columns: 1fr auto; }
  .brand { font-size: 17px; }
  .brand img { width: 42px; height: 42px; }
  .header-fact { display: none; }
  .top-nav { gap: 4px; }
  .top-nav a { padding-inline: 8px; font-size: 9px; }
  .provenance-rail { height: auto; padding-block: 6px; }
  .provenance-rail::before { top: 28px; }
  .rail-nav { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 4px; }
  .rail-nav a { grid-template-columns: 22px 1fr; min-width: 0; gap: 4px; padding-inline: 7px; }
  .rail-nav a::before { left: 1px; width: 4px; height: 4px; }
  .rail-nav span { font-size: 10px; }
  .rail-nav b { font-size: 10px; letter-spacing: 0; }
  .rail-nav a:focus-visible { outline-offset: -3px; }
  .ledger-section { scroll-margin-top: 124px; }
  .opening-copy { min-height: 570px; padding: 48px 19px 38px; }
  h1 { font-size: clamp(50px, 14vw, 64px); line-height: 0.88; }
  h2 { font-size: clamp(46px, 13vw, 64px); }
  h3 { font-size: 44px; }
  .opening-copy > p { font-size: 18px; }
  .live-model { min-height: 690px; padding: 42px 24px; }
  .live-model::before { left: 9px; }
  .live-model::after { right: 9px; }
  .model-head img { width: 58px; height: 58px; }
  .capture-fragment blockquote { font-size: 27px; }
  .source-origin { grid-template-columns: 1fr; gap: 12px; }
  .model-route::before, .model-route span { left: 24px; }
  .model-route span { width: calc(100% - 24px); }
  .model-facts { grid-template-columns: 1fr; }
  .model-facts div { display: grid; grid-template-columns: 1fr 1fr; padding: 8px 0; border-bottom: 1px solid var(--line); }
  .model-facts dd { margin-top: 0; text-align: right; }
  .proof, .mechanism, .composition-field, .privacy, .pricing { padding-inline: 19px; }
  .product-proof { margin-top: 48px; }
  .proof-labels { grid-template-columns: 1fr; }
  .proof-labels span:nth-child(2), .proof-labels span:last-child { text-align: left; }
  .app-frame { padding: 6px; }
  figcaption { display: grid; }
  .mechanism-heading h2 { margin-top: 30px; }
  .route-list { margin-top: 52px; }
  .route-list li { grid-template-columns: 38px 1fr; gap: 14px; padding-block: 27px 31px; }
  .assembly { margin-top: 52px; }
  .assembly > div { grid-template-columns: 42px 1fr; gap: 14px; }
  .assembly-index { font-size: 42px; }
  .assembly-format pre { padding: 18px; font-size: 11px; }
  .assembly-output > div:nth-child(2) p { font-size: 17px; }
  .privacy { min-height: 0; gap: 78px; }
  .privacy h2 { margin-top: 38px; font-size: clamp(56px, 17vw, 78px); }
  .privacy-copy > p:last-child { font-size: 17px; }
  .pricing { grid-template-columns: 1fr; }
  .price-mark, .price-copy, .purchase-panel { grid-column: auto; }
  .price-copy h2 { margin-top: 34px; }
  .purchase-panel { width: 100%; margin-top: 28px; }
  .site-footer { grid-template-columns: 1fr auto; min-height: 110px; }
  .site-footer p:nth-child(2) { display: none; }
}

@media (max-width: 390px) {
  .top-nav a:first-child { display: none; }
  .opening-copy { min-height: 540px; }
  .live-model { padding-inline: 20px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-delay: 0ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .model-route::before, .model-route span {
    transform: none;
  }
  .prompt-result { opacity: 1; clip-path: none; }
}