/* ============================================================
     ATLAS — case-study interior (chapter 1.01)
     Same monograph system as the index: left spine, single green
     signal, sans-led type with Newsreader as the quiet body voice,
     decimal page numbers, B&W imagery, tabular figures.
     The spine is recontextualised to THIS chapter — a back-to-index
     link, the project's metadata, and in-page section nav.
     ============================================================ */
  :root {
    --paper: #f4f2ec;
    --paper-deep: #e9e4d8;
    --ink: #161514;
    --ink-2: #4a4744;
    --ink-3: #807c75;
    --ink-4: #b7b1a4;
    --rule: rgba(22,21,20,0.14);
    --rule-soft: rgba(22,21,20,0.06);
    --signal: #2f7d4f;

    --sans:    'Hanken Grotesk', 'Helvetica Neue', system-ui, sans-serif;
    --display: 'Bricolage Grotesque', 'Hanken Grotesk', sans-serif;
    --serif:   'Newsreader', Georgia, serif;
    --mono:    'JetBrains Mono', ui-monospace, monospace;

    --spine: 248px;
    --gutter: 56px;

    --pad: 28px;
    --col-gap: 64px;
    --band: 92px;
    --overlay: rgba(10,10,8,0.94);
    --grain: rgba(22,21,20,0.018);
  }
  html[data-theme="ink"] {
    --paper: #14130f;
    --paper-deep: #1d1b15;
    --ink: #ece8db;
    --ink-2: #b8b3a3;
    --ink-3: #969283;
    --ink-4: #8a8276;
    --rule: rgba(236,232,219,0.16);
    --rule-soft: rgba(236,232,219,0.06);
    --signal: #5ec27a;
  }
  html[data-theme="paper-cool"] {
    --paper: #ecedee;
    --paper-deep: #dfe1e3;
    --ink: #0e1114;
    --ink-2: #404448;
    --ink-3: #707479;
    --ink-4: #aaaeb2;
    --rule: rgba(14,17,20,0.14);
    --rule-soft: rgba(14,17,20,0.06);
    --signal: #1f7a5e;
  }
  html[data-accent="forest"]  { --signal: #2f7d4f; }
  html[data-accent="moss"]    { --signal: #4a6b2e; }
  html[data-accent="deep"]    { --signal: #134e36; }
  html[data-accent="ink"]     { --signal: var(--ink); }
  html[data-theme="ink"][data-accent="ink"] { --signal: var(--ink-2); }
  html[data-theme="ink"][data-accent="forest"] { --signal: #74d295; }
  html[data-theme="ink"][data-accent="moss"]   { --signal: #bcd170; }
  html[data-theme="ink"][data-accent="deep"]   { --signal: #4ccb93; }

  * { box-sizing: border-box; }
  html, body {
    margin: 0; padding: 0;
    background: var(--paper);
    color: var(--ink);
    font-family: var(--sans);
    font-feature-settings: "ss01", "ss02", "tnum";
    -webkit-font-smoothing: antialiased;
    transition: background-color .35s ease, color .35s ease;
  }
  ::selection { background: var(--signal); color: var(--paper); }

  .page { max-width: 1440px; margin: 0 auto; padding: 0 var(--gutter); position: relative; }

  body::before {
    content: ""; position: fixed; inset: 0;
    background-image: radial-gradient(var(--grain) 1px, transparent 1px);
    background-size: 3px 3px; pointer-events: none; z-index: 1;
  }

  image-slot {
    --is-bg: var(--paper-deep);
    --is-border: var(--rule);
    --is-text: var(--ink-3);
    display: block; width: 100%; height: 100%;
  }
  image-slot::part(image) { filter: grayscale(1) contrast(1.02); }

  .signal-dot {
    width: 7px; height: 7px; border-radius: 50%;
    background: var(--signal); display: inline-block;
    margin-right: 6px; vertical-align: middle;
  }

  /* ============================================================
     SPREAD + SPINE
     ============================================================ */
  .spread {
    display: grid;
    grid-template-columns: var(--spine) 1fr;
    gap: var(--gutter);
    position: relative; z-index: 2;
  }
  .spine {
    position: sticky; top: 0; align-self: start;
    height: 100vh; padding: var(--pad) 24px var(--pad) 0;
    border-right: 1px solid var(--rule);
    display: flex; flex-direction: column;
    font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.02em;
  }
  .spine .lockup {
    display: flex; align-items: baseline; gap: 10px;
    color: var(--ink); font-size: 0.8125rem; letter-spacing: 0;
  }
  .spine .lockup .mark {
    width: 22px; height: 22px; border: 1px solid var(--ink);
    display: inline-flex; align-items: center; justify-content: center;
    font-family: var(--display); font-weight: 600; font-size: 0.75rem;
    line-height: 1; letter-spacing: -0.02em;
  }
  .spine .lockup b { font-family: var(--sans); font-weight: 600; }

  .spine-back {
    margin-top: 22px;
    display: inline-flex; align-items: center; gap: 8px;
    color: var(--ink-2); text-decoration: none;
    font-size: 0.75rem; letter-spacing: 0.02em;
    padding-bottom: 18px; border-bottom: 1px solid var(--rule);
  }
  .spine-back .arr { color: var(--signal); transition: transform .2s ease; }
  .spine-back:hover { color: var(--ink); }
  .spine-back:hover .arr { transform: translateX(-3px); }

  .spine-meta { margin-top: 24px; display: grid; gap: 13px; }
  .spine-meta dt {
    font-size: 0.75rem; color: var(--ink-4);
    text-transform: uppercase; letter-spacing: 0.12em;
  }
  .spine-meta dd { margin: 2px 0 0; color: var(--ink); font-size: 0.875rem; letter-spacing: 0; }

  .spine-nav {
    margin-top: auto; display: grid; gap: 4px;
    padding-top: 24px; border-top: 1px solid var(--rule);
  }
  .spine-nav a {
    color: var(--ink-2); text-decoration: none; font-size: 0.875rem;
    display: flex; justify-content: space-between; align-items: baseline;
    padding: 4px 0; letter-spacing: 0;
  }
  .spine-nav a span { color: var(--ink-4); font-family: var(--mono); font-size: 0.75rem; }
  .spine-nav a:hover, .spine-nav a.current { color: var(--ink); }
  .spine-nav a:hover span, .spine-nav a.current span { color: var(--signal); }

  .spine-foot {
    margin-top: 18px; padding-top: 18px; border-top: 1px solid var(--rule);
    font-size: 0.75rem; color: var(--ink-4);
    display: flex; justify-content: space-between; letter-spacing: 0.04em;
  }

  /* ============================================================
     BODY
     ============================================================ */
  .body { padding: var(--pad) 0 0; }
  .band { padding-top: var(--band); }

  /* ----- CHAPTER OPENER ----- */
  .cs-top {
    display: flex; justify-content: space-between; align-items: baseline;
    padding: var(--pad) 0 26px; border-bottom: 1px solid var(--rule);
    font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.02em;
  }
  .cs-top .crumb b { color: var(--ink); font-weight: 500; }
  .cs-top .pp b { color: var(--signal); font-weight: 500; }

  .cs-eyebrow {
    margin-top: var(--gutter);
    display: flex; gap: 14px; align-items: center;
    font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.08em; text-transform: uppercase;
  }
  .cs-eyebrow b { color: var(--ink); font-weight: 500; }
  .cs-eyebrow .sep { width: 16px; height: 1px; background: var(--rule); }

  .cs-title {
    margin: 22px 0 0; max-width: 16ch;
    font-family: var(--display); font-weight: 500;
    font-size: clamp(56px, 7.4vw, 108px);
    line-height: 0.92; letter-spacing: -0.04em; color: var(--ink);
    text-wrap: balance;
  }
  .cs-title .stop { color: var(--signal); }

  .cs-deck {
    margin: 36px 0 0; max-width: 30ch;
    font-family: var(--serif); font-weight: 400;
    font-size: clamp(22px, 2vw, 28px); line-height: 1.34;
    letter-spacing: -0.01em; color: var(--ink-2);
  }
  .cs-deck .u {
    color: var(--ink);
    background-image: linear-gradient(to right, var(--signal), var(--signal));
    background-position: 0 95%; background-size: 100% 1.5px;
    background-repeat: no-repeat; padding-bottom: 2px;
  }

  .cs-facts {
    margin-top: 48px; padding-top: 26px; border-top: 1px solid var(--rule);
    display: grid; grid-template-columns: repeat(5, 1fr); gap: var(--pad);
    font-family: var(--mono); font-size: 0.875rem;
  }
  .cs-facts dt {
    font-size: 0.75rem; color: var(--ink-4);
    text-transform: uppercase; letter-spacing: 0.1em;
  }
  .cs-facts dd { margin: 8px 0 0; color: var(--ink); letter-spacing: 0; line-height: 1.5; }

  /* ----- HERO PLATE ----- */
  .cs-hero { margin-top: 48px; }
  .cs-hero .plate {
    aspect-ratio: 21 / 9; background: var(--paper-deep);
    border: 1px solid var(--rule); overflow: hidden; position: relative;
  }
  .cs-hero figcaption {
    margin-top: 12px; display: flex; justify-content: space-between;
    font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.04em; text-transform: uppercase;
  }
  .cs-hero figcaption .n { color: var(--ink); }

  /* ----- SECTION HEAD ----- */
  .head {
    padding: 14px 0 0; border-top: 1px solid var(--ink);
    display: grid; grid-template-columns: 1fr auto;
    align-items: baseline; gap: 24px;
  }
  .head h2 {
    margin: 0; font-family: var(--display); font-weight: 500;
    font-size: clamp(40px, 4.4vw, 60px); line-height: 0.96;
    letter-spacing: -0.035em; color: var(--ink);
  }
  .head h2 .u {
    background-image: linear-gradient(to right, var(--signal), var(--signal));
    background-position: 0 90%; background-size: 100% 2px;
    background-repeat: no-repeat; padding-bottom: 4px;
  }
  .head .tag {
    text-align: right; font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.02em; white-space: nowrap;
  }

  /* ----- PROSE + TWO-COLUMN ----- */
  .two {
    display: grid; grid-template-columns: 1fr 1fr; gap: var(--col-gap);
    padding-top: 36px; align-items: start;
  }
  .lead-serif {
    margin: 0; font-family: var(--display); font-weight: 500;
    font-size: clamp(26px, 2.6vw, 34px); line-height: 1.14;
    letter-spacing: -0.025em; color: var(--ink); max-width: 18ch;
  }
  .prose p {
    margin: 0 0 18px; font-family: var(--serif);
    font-size: 1.1875rem; line-height: 1.58; color: var(--ink);
    letter-spacing: -0.003em; max-width: 56ch;
  }
  .prose p:last-child { margin-bottom: 0; }
  .prose p b { font-weight: 600; }
  .prose .mark {
    background-image: linear-gradient(to right, var(--signal), var(--signal));
    background-position: 0 92%; background-size: 100% 1.5px;
    background-repeat: no-repeat; padding-bottom: 1px;
  }

  /* at-a-glance stat list */
  .glance { display: grid; gap: 0; }
  .glance .row {
    display: grid; grid-template-columns: 1fr auto; align-items: baseline;
    gap: 16px; padding: 16px 0; border-bottom: 1px solid var(--rule);
  }
  .glance .row:first-child { border-top: 1px solid var(--rule); }
  .glance .k {
    font-family: var(--mono); font-size: 0.75rem; color: var(--ink-3);
    letter-spacing: 0.04em; text-transform: uppercase;
  }
  .glance .v {
    font-family: var(--display); font-weight: 500;
    font-size: 1.875rem; line-height: 1; letter-spacing: -0.02em; color: var(--ink);
  }
  .glance .v small {
    font-family: var(--mono); font-size: 0.75rem; font-weight: 400;
    color: var(--ink-3); letter-spacing: 0; text-transform: uppercase; margin-left: 6px;
  }

  /* ----- APPROACH STEPS ----- */
  .steps {
    margin-top: 36px; display: grid;
    grid-template-columns: repeat(3, 1fr); gap: 1px;
    background: var(--rule); border: 1px solid var(--rule);
  }
  .step { background: var(--paper); padding: 26px 24px 30px; }
  .step .no {
    font-family: var(--mono); font-size: 0.75rem; color: var(--signal);
    letter-spacing: 0.04em;
  }
  .step h3 {
    margin: 18px 0 10px; font-family: var(--display); font-weight: 500;
    font-size: 1.375rem; line-height: 1.1; letter-spacing: -0.02em; color: var(--ink);
  }
  .step p {
    margin: 0; font-family: var(--serif); font-size: 1rem;
    line-height: 1.5; color: var(--ink-2);
  }

  /* ----- FIGURE GRID ----- */
  .figs {
    margin-top: 40px; display: grid;
    grid-template-columns: 1fr 1fr; gap: 24px;
  }
  .figure { margin: 0; }
  .figure .plate {
    aspect-ratio: 4 / 3; background: var(--paper-deep);
    border: 1px solid var(--rule); overflow: hidden;
  }
  .figure.tall .plate { aspect-ratio: 3 / 4; }
  .figure.wide { grid-column: 1 / -1; }
  .figure.wide .plate { aspect-ratio: 21 / 9; }
  .figure figcaption {
    margin-top: 10px; display: flex; gap: 12px;
    font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.04em; text-transform: uppercase;
  }
  .figure figcaption .n { color: var(--ink); }

  /* ----- PULL QUOTE ----- */
  .pull {
    margin: 0; padding: 80px 0; text-align: center;
    border-top: 1px solid var(--rule); border-bottom: 1px solid var(--rule);
  }
  .pull blockquote {
    margin: 0 auto; max-width: 22ch;
    font-family: var(--display); font-weight: 500;
    font-size: clamp(34px, 4.4vw, 60px); line-height: 1.05;
    letter-spacing: -0.035em; color: var(--ink); text-wrap: balance;
  }
  .pull blockquote .stop { color: var(--signal); }
  .pull figcaption {
    margin-top: var(--pad); font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.06em; text-transform: uppercase;
  }

  /* ----- METRICS ----- */
  .metrics {
    margin-top: 40px; display: grid;
    grid-template-columns: repeat(4, 1fr); border: 1px solid var(--rule);
  }
  .metric {
    padding: 32px 26px; border-right: 1px solid var(--rule);
  }
  .metric:last-child { border-right: 0; }
  .metric .v {
    font-family: var(--display); font-weight: 500;
    font-size: clamp(40px, 4.2vw, 56px); line-height: 0.95;
    letter-spacing: -0.035em; color: var(--ink);
  }
  .metric .v .unit { color: var(--signal); }
  .metric .k {
    margin-top: 14px; font-family: var(--mono); font-size: 0.75rem;
    color: var(--ink-3); letter-spacing: 0.02em; line-height: 1.5;
  }

  /* ----- NEXT / FOOT ----- */
  .next {
    margin-top: var(--band); padding: 44px 0; border-top: 1px solid var(--ink);
    display: grid; grid-template-columns: auto 1fr; gap: 40px; align-items: center;
    text-decoration: none; color: inherit;
  }
  .next .lbl {
    font-family: var(--mono); font-size: 0.75rem; color: var(--ink-3);
    letter-spacing: 0.06em; text-transform: uppercase;
  }
  .next .nm {
    margin: 10px 0 0; font-family: var(--display); font-weight: 500;
    font-size: clamp(40px, 5vw, 72px); line-height: 0.94;
    letter-spacing: -0.04em; color: var(--ink);
  }
  .next .arr {
    justify-self: end; font-family: var(--display); font-weight: 400;
    font-size: clamp(44px, 6vw, 84px); color: var(--signal);
    transition: transform .25s ease;
  }
  .next:hover .arr { transform: translateX(12px); }
  .next:hover .nm { color: var(--signal); }

  .foot {
    margin-top: 18px; padding: 18px 0 var(--gutter); border-top: 1px solid var(--rule);
    display: flex; justify-content: space-between; align-items: baseline;
    font-family: var(--mono); font-size: 0.75rem; color: var(--ink-3); letter-spacing: 0.02em;
  }
  .foot b { color: var(--ink); font-weight: 500; }

  /* ----- REVEAL ----- */
  .js .reveal { opacity: 0; transform: translateY(20px); transition: opacity .8s ease, transform .8s ease; }
  .js .reveal.in { opacity: 1; transform: translateY(0); }
  @media (prefers-reduced-motion: reduce) {
    .js .reveal { opacity: 1; transform: none; transition: none; }
  }

  /* ----- HAMBURGER (mobile only) ----- */
  .spine-menu { display: contents; }
  .spine-toggle {
    display: none;
    align-items: center; gap: 9px;
    background: none; border: 0; cursor: pointer;
    padding: 6px 0; color: var(--ink);
    font-family: var(--mono); font-size: 0.75rem;
    letter-spacing: 0.06em; text-transform: uppercase;
    -webkit-tap-highlight-color: transparent;
  }
  .spine-toggle .lbl { color: var(--ink-2); }
  .spine-toggle .bars { position: relative; width: 22px; height: 1.5px; margin: 5px 0; background: var(--ink); display: inline-block; transition: background .2s ease; }
  .spine-toggle .bars::before,
  .spine-toggle .bars::after {
    content: ""; position: absolute; left: 0; right: 0; height: 1.5px;
    background: var(--ink); transition: transform .28s ease, top .28s ease;
  }
  .spine-toggle .bars::before { top: -6px; }
  .spine-toggle .bars::after  { top: 6px; }
  .spine.open .spine-toggle .bars { background: transparent; }
  .spine.open .spine-toggle .bars::before { top: 0; transform: rotate(45deg); }
  .spine.open .spine-toggle .bars::after  { top: 0; transform: rotate(-45deg); }
  .spine.open .spine-toggle .lbl { color: var(--signal); }

  /* ============================================================
     RESPONSIVE — tablet & mobile
     ============================================================ */
  @media (max-width: 1080px) {
    .page { padding: 0 40px; }
    :root { --gutter: 40px; --spine: 210px; }
    .cs-facts { grid-template-columns: repeat(3, 1fr); gap: 24px; }
  }

  @media (max-width: 860px) {
    .page { padding: 0 28px; }

    /* spine → sticky top bar with hamburger */
    .spread { grid-template-columns: 1fr; gap: 0; }
    .spine {
      position: sticky; top: 0; z-index: 60;
      height: auto;
      flex-direction: row; flex-wrap: wrap; align-items: center;
      gap: 0 16px; padding: 14px 0; margin-bottom: 4px;
      border-right: none; border-bottom: 1px solid var(--rule);
      background: var(--paper);
    }
    .spine .lockup { font-size: 0.875rem; position: relative; z-index: 62; }
    .spine-toggle { display: inline-flex; margin-left: auto; position: relative; z-index: 62; }

    /* full-cover overlay menu — covers the page, sits below the bar row */
    .spine-menu {
      display: block;
      position: fixed; inset: 0; z-index: 55;
      margin: 0;
      padding: 78px 28px 32px;
      background: var(--paper);
      overflow-y: auto;
      opacity: 0; visibility: hidden;
      transform: translateY(-8px);
      transition: opacity .26s ease, transform .26s ease, visibility 0s linear .26s;
    }
    .spine.open .spine-menu {
      opacity: 1; visibility: visible; transform: none;
      transition: opacity .26s ease, transform .26s ease, visibility 0s;
    }
    .spine.open { background: var(--paper); border-bottom-color: transparent; }
    html:has(.spine.open) body { overflow: hidden; }
    .spine-back {
      display: inline-flex; margin: 8px 0 0 !important;
      padding: 0; border-bottom: none;
    }
    .spine-meta {
      display: grid; gap: 16px;
      padding: 22px 0 0; margin-top: 22px !important;
      border-top: 1px solid var(--rule);
    }
    .spine-nav {
      display: grid; gap: 2px;
      padding: 22px 0 0; margin-top: 22px !important;
      border-top: 1px solid var(--rule);
    }
    .spine-nav a { padding: 10px 0; font-size: 1.1875rem; }
    .spine-nav a span { display: inline; }
    .spine-foot {
      display: flex; padding: 20px 0 0; margin-top: 22px !important;
      border-top: 1px solid var(--rule);
    }
    .body { padding-top: 20px; }

    .band { padding-top: 64px; }
    .cs-top { flex-direction: column; gap: 4px; align-items: flex-start; }
    .cs-eyebrow { flex-wrap: wrap; gap: 8px; }
    .cs-facts { grid-template-columns: 1fr 1fr; gap: 20px; }

    .head { grid-template-columns: 1fr; gap: 8px; }
    .head .tag { text-align: left; }

    .two { grid-template-columns: 1fr; gap: 28px; }
    .lead-serif { max-width: none; }
    .steps { grid-template-columns: 1fr; }
    .figs { grid-template-columns: 1fr; }
    .figure.wide { grid-column: auto; }
    .metrics { grid-template-columns: 1fr 1fr; }
    .metric:nth-child(2) { border-right: 0; }
    .metric:nth-child(1), .metric:nth-child(2) { border-bottom: 1px solid var(--rule); }

    .next { grid-template-columns: 1fr; gap: 16px; }
    .next .arr { justify-self: start; }
    .foot { flex-direction: column; gap: 6px; align-items: flex-start; }
  }

  @media (max-width: 480px) {
    .page { padding: 0 18px; }
    .spine-nav { width: 100%; margin-left: 0; }
    .cs-facts { grid-template-columns: 1fr 1fr; }
    .metrics { grid-template-columns: 1fr; }
    .metric { border-right: 0; border-bottom: 1px solid var(--rule); }
    .metric:last-child { border-bottom: 0; }
    .cs-hero .plate { aspect-ratio: 4 / 3; }
  }

/* ===== production additions (real images, a11y, lightbox) ===== */
.reader-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.skip-link:focus{position:fixed;top:12px;left:12px;width:auto;height:auto;clip:auto;z-index:999;background:var(--signal);color:var(--paper);padding:8px 14px;font-family:var(--mono);font-size:0.875rem}
[hidden]{display:none!important}
a{color:inherit}
a:hover{color:var(--signal)}

.cs-hero .plate img,.figure .plate img{width:100%;height:100%;object-fit:cover;object-position:top;filter:grayscale(1) contrast(1.02);display:block}
.cs-link{display:inline-flex;align-items:center;gap:8px;margin-top:22px;font-family:var(--mono);font-size:0.875rem;letter-spacing:.06em;text-transform:uppercase;text-decoration:none;color:var(--signal);border-bottom:1px solid var(--signal);padding-bottom:3px}
.lightbox{position:fixed;inset:0;z-index:200;background:var(--overlay);display:grid;place-items:center;padding:48px 24px;overflow:auto}
.lightbox img{max-width:min(1200px,100%);height:auto;filter:grayscale(1)}
.lightbox .lb-close{position:fixed;top:16px;right:20px;background:none;border:0;color:var(--signal);font-size:2.5rem;line-height:1;cursor:pointer}

.cs-facts{grid-template-columns:repeat(auto-fit,minmax(150px,1fr))}