:root{--white:#fff;--paper:#faf9f8;--ink:#272124;--muted:#777074;--line:#ded9db;--red:#86172a;--red-soft:#f5e9eb;--green:#29423a;--green-soft:#e8efeb;--gold:#b4935c;--max:1580px;--header:72px;font-family:Inter,ui-sans-serif,-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;color-scheme:light;font-synthesis:none}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;color:var(--ink);background:var(--white)}a{color:inherit;text-decoration:none}button{font:inherit}.skip-link{position:fixed;left:16px;top:-80px;z-index:100;padding:10px 14px;color:#fff;background:var(--red)}.skip-link:focus{top:12px}
.site-header{position:fixed;inset:0 0 auto;z-index:30;height:var(--header);display:grid;grid-template-columns:1fr auto 1fr;align-items:center;padding:0 clamp(24px,4vw,72px);background:rgba(255,255,255,.92);border-bottom:1px solid rgba(39,33,36,.08);backdrop-filter:blur(18px)}.brand{justify-self:start;font:650 19px/1 Georgia,serif;letter-spacing:-.03em}.brand span{color:var(--red)}.header-center{font-size:10px;letter-spacing:.22em;color:var(--muted)}.header-link{justify-self:end;padding-bottom:4px;border-bottom:1px solid var(--ink);font-size:12px}
.chapter-rail{position:fixed;top:50%;right:clamp(18px,2.2vw,42px);z-index:20;display:flex;flex-direction:column;gap:10px;transform:translateY(-50%)}.rail-item{position:relative;display:grid;grid-template-columns:34px 22px;gap:8px;align-items:center;width:64px;padding:5px 0;border:0;color:#9f999c;background:transparent;cursor:pointer;text-align:left}.rail-item i{width:13px;height:1px;justify-self:end;background:#bdb7ba;transition:.25s}.rail-item b{font:500 10px/1 ui-monospace,SFMono-Regular,Menlo,monospace}.rail-item span{position:absolute;right:61px;top:50%;width:max-content;padding:7px 10px;color:#fff;background:var(--ink);font-size:11px;opacity:0;pointer-events:none;transform:translate(6px,-50%);transition:.2s}.rail-item:hover span,.rail-item:focus-visible span{opacity:1;transform:translate(0,-50%)}.rail-item.is-active{color:var(--red)}.rail-item.is-active i{width:34px;background:var(--red)}
.screen{position:relative;display:grid;grid-template-columns:minmax(0,4.1fr) minmax(230px,1.15fr);gap:clamp(34px,5vw,80px);min-height:100svh;max-width:var(--max);margin:auto;padding:clamp(120px,13vh,160px) clamp(86px,8vw,140px) 92px clamp(36px,7vw,116px);scroll-margin-top:var(--header);align-items:start}.screen-main{min-width:0}.hero{grid-template-columns:minmax(0,1.38fr) minmax(230px,.72fr);align-items:center;padding-top:clamp(130px,17vh,190px)}.hero-main{align-self:center}.kicker{display:flex;gap:24px;margin:0 0 32px;color:var(--red);font-size:10px;letter-spacing:.19em}.kicker span+span{color:var(--muted)}h1{max-width:860px;margin:0;font-size:clamp(48px,5.5vw,88px);font-weight:570;line-height:1.04;letter-spacing:-.065em}h1 em{font-style:normal;color:var(--red)}.hero-lead{max-width:550px;margin:28px 0 0;color:#696267;font-size:17px;line-height:1.8;letter-spacing:-.02em}.design-note{align-self:center;position:sticky;top:130px;min-height:245px}.note-rule{width:100%;height:1px;margin-bottom:14px;background:#d8d3d5}.design-note>span{color:var(--red);font-size:9px;letter-spacing:.18em}.design-note h2{margin:28px 0 17px;font-size:clamp(22px,1.8vw,30px);font-weight:540;line-height:1.28;letter-spacing:-.04em}.design-note p{margin:0;color:#5f585c;font-size:13px;line-height:1.9}.keyword-row{display:flex;flex-wrap:wrap;gap:8px;margin-top:28px}.keyword-row b{padding:8px 10px;color:var(--red);background:var(--red-soft);font-size:10px;font-weight:500}.note-list{margin:32px 0 0;border-top:1px solid #e3dfe0}.note-list div{display:grid;grid-template-columns:48px 1fr;gap:14px;padding:13px 0;border-bottom:1px solid #e3dfe0}.note-list dt{color:var(--red);font-size:10px}.note-list dd{margin:0;color:#686165;font-size:11px}.note-emphasis{margin-top:26px!important;padding:18px 0 0;border-top:1px solid #e3dfe0;color:var(--red)!important}.scroll-cue{position:absolute;left:clamp(36px,7vw,116px);bottom:42px;display:flex;align-items:center;gap:12px;color:var(--muted);font-size:10px;letter-spacing:.12em}.scroll-cue i{width:46px;height:1px;background:var(--red)}
.section-heading{display:flex;gap:18px;align-items:flex-start;margin-bottom:42px}.section-heading>span{color:var(--red);font:500 12px/1 ui-monospace,SFMono-Regular,Menlo,monospace}.section-heading p{margin:-2px 0 8px;color:var(--muted);font-size:9px;letter-spacing:.2em}.section-heading h2{margin:0;font-size:clamp(35px,4.4vw,64px);font-weight:520;line-height:1;letter-spacing:-.055em}
.path-canvas{position:relative;display:grid;grid-template-columns:repeat(4,1fr);gap:16px;min-height:430px;padding:112px 0 62px}.path-line{position:absolute;left:8%;right:8%;top:205px;height:1px;background:linear-gradient(90deg,var(--red),#d8c8ca 72%,#e7e3e4)}.path-node{position:relative;z-index:1;display:flex;flex-direction:column;justify-content:center;min-height:185px;padding:24px 20px;background:#fff;border:1px solid var(--line);box-shadow:0 16px 34px rgba(39,33,36,.07)}.path-node:after{content:"";position:absolute;top:50%;right:-18px;width:19px;height:1px;background:var(--line)}.path-node:last-of-type:after{display:none}.path-node.primary{border-color:var(--red);background:var(--red);color:#fff;transform:translateY(-16px)}.path-node.future{background:var(--paper)}.path-node small{margin-bottom:15px;color:var(--red);font:500 9px ui-monospace,SFMono-Regular,Menlo,monospace;letter-spacing:.12em}.path-node.primary small{color:#f4dce1}.path-node strong{font-size:19px;font-weight:560;line-height:1.35}.path-node span{margin-top:12px;color:var(--muted);font-size:11px;line-height:1.6}.path-node.primary span{color:#f1dfe2}.path-caption{position:absolute;left:0;bottom:20px;color:var(--red);font-size:11px;letter-spacing:.08em}.path-caption span{padding:0 10px;color:#c8bfc2}
.foundation-board{padding-top:2px}.evidence-strip{display:grid;grid-template-columns:1.55fr .72fr .72fr;gap:clamp(16px,2vw,28px);align-items:end}.phone{position:relative;margin:0;outline:none;cursor:zoom-in;filter:drop-shadow(0 24px 36px rgba(39,33,36,.13));transition:transform .25s ease}.phone:hover{transform:translateY(-6px)}.phone:focus-visible{outline:2px solid var(--red);outline-offset:5px}.phone img{display:block;width:100%;height:auto;background:#f4f5f5;border:8px solid #272124;border-radius:27px}.phone-label{position:absolute;top:-23px;left:5px;color:var(--red);font-size:10px;letter-spacing:.12em}.small-phone{max-width:220px;justify-self:center}.data-chain{display:flex;align-items:center;gap:14px;margin:46px 3% 28px;color:var(--red);font-size:12px}.data-chain i{height:1px;flex:1;background:linear-gradient(90deg,var(--red),#d9cdd0)}.map-lane{display:grid;grid-template-columns:1fr 30px 1.2fr 30px 1.5fr;align-items:center;gap:10px;padding:20px 22px;color:#655e62;background:var(--paper);border-top:1px solid var(--line);border-bottom:1px solid var(--line);font-size:12px}.map-lane b{color:var(--red);font-size:17px;text-align:center}.map-origin,.map-end{color:var(--red);font-weight:550}
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footer{grid-column:1/-1;display:flex;justify-content:space-between;margin-top:52px;padding-top:20px;border-top:1px solid var(--ink);color:var(--muted);font-size:9px;letter-spacing:.13em}footer a{color:var(--red)}
.lightbox{width:min(95vw,1100px);max-height:94vh;padding:48px 24px 24px;border:0;background:#fff;box-shadow:0 30px 100px rgba(0,0,0,.28)}.lightbox::backdrop{background:rgba(39,33,36,.72);backdrop-filter:blur(8px)}.lightbox>button{position:absolute;right:18px;top:8px;padding:4px 10px;border:0;color:var(--ink);background:transparent;cursor:pointer;font-size:28px;font-weight:250}.lightbox>div{max-height:calc(94vh - 76px);overflow:auto}.lightbox img{display:block;width:100%;height:auto}
@media(max-width:1080px){.screen{padding-right:88px}.hero{grid-template-columns:minmax(0,1fr) 210px;gap:32px}.path-canvas{gap:10px}.path-node{padding:20px 14px}.path-node strong{font-size:16px}}
@media(max-width:760px){:root{--header:60px}.site-header{grid-template-columns:1fr auto;padding:0 20px}.header-center{display:none}.chapter-rail{top:auto;left:0;right:0;bottom:0;transform:none;flex-direction:row;justify-content:center;gap:2px;padding:8px;background:rgba(255,255,255,.94);border-top:1px solid #e4e0e2}.rail-item{grid-template-columns:1fr;width:48px;justify-content:center}.rail-item i,.rail-item span{display:none}.rail-item b{text-align:center}.rail-item.is-active b{padding-bottom:4px;border-bottom:2px solid var(--red)}.screen,.hero{display:block;min-height:auto;padding:100px 22px 88px}.hero{padding-top:110px}.kicker{display:block;line-height:1.6}.kicker span{display:block;margin-bottom:6px}h1{font-size:clamp(45px,13vw,68px)}.hero-lead{font-size:15px}.design-note{position:static;min-height:0;margin-top:64px}.scroll-cue{display:none}.hero-stack{margin-top:90px;min-height:450px;transform:scale(.92);transform-origin:top center}.section-heading{margin-bottom:46px}.section-heading h2{font-size:clamp(34px,10vw,48px)}.path-canvas{grid-template-columns:1fr;gap:13px;min-height:0;padding:0 0 44px}.path-line{left:23px;right:auto;top:28px;bottom:55px;width:1px;height:auto;background:linear-gradient(var(--red),#ddd5d7)}.path-node{min-height:0;margin-left:48px;padding:18px}.path-node:after{top:auto;right:auto;bottom:-14px;left:-26px;width:26px}.path-node.primary{transform:none}.path-caption{bottom:0}.evidence-strip{grid-template-columns:1fr 1fr;gap:34px 16px;align-items:start;padding:20px 18px 0}.main-phone{grid-column:1/-1;max-width:250px;justify-self:center}.small-phone{max-width:150px}.data-chain{margin:42px 0 24px;gap:8px;font-size:10px}.map-lane{grid-template-columns:1fr;gap:7px;text-align:center}.map-lane b{transform:rotate(90deg)}.ai-board{grid-template-columns:1fr;gap:62px;padding-top:0}.ai-phone{max-width:220px}.ai-step{grid-template-columns:34px 1fr;gap:13px;padding:15px}.ai-step small{width:34px;height:34px}.ai-step strong{font-size:16px}.ai-step p{font-size:11px}footer{margin-bottom:46px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}.phone:hover{transform:none}}

/* Compact case-study frame: keep each desktop chapter within one viewport. */
@media(min-width:761px){
  .screen{height:100svh;min-height:100svh;padding-top:clamp(96px,11vh,132px);padding-bottom:72px;overflow:hidden}
  .hero{padding-top:clamp(108px,13vh,150px)}
  h1{font-size:clamp(42px,4.8vw,76px)}
  .kicker{margin-bottom:clamp(20px,3vh,32px)}
  .hero-lead{margin-top:clamp(18px,2.5vh,28px);font-size:clamp(14px,1.2vw,17px);line-height:1.7}
  .phone-stack{position:relative;width:min(100%,520px);height:clamp(300px,39svh,430px);margin-top:clamp(30px,4vh,52px)}
  .phone-stack .phone{position:absolute}
  .phone-stack .phone img{width:100%;height:auto}
  .phone-itinerary{left:2%;top:9%;width:min(31%,185px);transform:rotate(-8deg)}
  .phone-tasks{right:9%;top:16%;width:min(27%,165px);transform:rotate(7deg)}
  .phone-front{left:27%;top:0;width:min(34%,205px);z-index:2}
  .phone-stack .phone:hover{z-index:4;transform:translateY(-6px) rotate(0)}
  .section-heading{margin-bottom:clamp(24px,4vh,42px)}
  .section-heading h2{font-size:clamp(32px,4vw,58px)}
  .path-canvas{min-height:clamp(300px,42svh,430px);padding:clamp(70px,10vh,112px) 0 48px}
  .path-line{top:clamp(145px,19vh,205px)}
  .path-node{min-height:clamp(135px,17vh,185px);padding:20px 18px}
  .foundation-board{padding-top:0}
  .evidence-strip{height:clamp(270px,42svh,470px)}
  .evidence-phone img{width:auto;max-width:100%;height:clamp(250px,42svh,470px);object-fit:contain;margin-inline:auto}
  .small-phone img{height:clamp(210px,31svh,350px)}
  .data-chain{margin-top:clamp(22px,4vh,46px);margin-bottom:22px}
  .ai-board{padding-top:8px}
  .ai-phone img{height:clamp(280px,45svh,500px);width:auto;max-width:100%;object-fit:contain}
  .ai-ladder{gap:9px}
  .ai-step{padding:13px 18px;gap:16px}
  .ai-step small{width:36px;height:36px}
  .ai-step strong{font-size:16px}
  .ai-step p{margin-top:4px;font-size:11px;line-height:1.45}
}

@media(max-width:760px){
  .screen,.hero{height:auto;min-height:auto;overflow:visible}
  .phone-stack{height:430px}
  .evidence-strip{height:auto}
  .evidence-phone img,.small-phone img,.ai-phone img{height:auto}
}