@font-face{font-family:Libre;src:url('/assets/fonts/libre-baskerville.ttf');font-display:swap}@font-face{font-family:Source;src:url('/assets/fonts/source-sans-3.ttf');font-display:swap}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:100px}body{margin:0;background:#101215;color:#e6e5de;font:19px/1.65 Source,Arial,sans-serif}a{color:inherit;text-decoration:none}button,input{font:inherit}button,a,input{touch-action:manipulation}button:focus-visible,a:focus-visible,input:focus-visible{outline:2px solid #48768f;outline-offset:5px}button{cursor:pointer}header{position:sticky;top:0;z-index:20;display:flex;justify-content:space-between;align-items:center;padding:25px 5vw;background:#101215;border-bottom:1px solid #343639}.brand{font-family:Libre,serif;font-size:19px;display:flex;gap:13px;align-items:center}.brand svg{width:25px;height:25px}nav{display:flex;gap:35px;font-size:16px}nav a{color:#9b9e9d}nav a.active,nav a:hover{color:#f0eee5}nav a.active{text-decoration:underline;text-underline-offset:8px;text-decoration-thickness:1px}.wrap{width:min(1200px,88vw);margin:auto}h1,h2,blockquote,.serif{font-family:Libre,Georgia,serif;font-weight:400}h1{font-size:clamp(42px,4.7vw,67px);line-height:1.26;letter-spacing:-.035em;margin:0}h2{font-size:clamp(32px,3.2vw,46px);line-height:1.35;letter-spacing:-.035em;margin:0 0 30px}h3{font-size:21px;font-weight:500}p{margin:0 0 25px;color:#aeb1b2}.hero{padding:88px 0 105px}.hero-layout{display:grid;grid-template-columns:1.2fr 1fr;gap:70px;align-items:center}.hero-copy{padding-bottom:20px}.hero-intro{font-size:16px;color:#9da6aa;margin-bottom:45px}.hero-copy>p:not(.hero-intro){font-size:19px;max-width:470px;margin:34px 0 0}.textlink{display:inline-flex;align-items:center;gap:32px;border-bottom:1px solid currentColor;padding:4px 0;font-size:16px;margin-top:34px}.brand-plate{background:#d5d4cc;color:#414640;min-width:0}.brand-plate svg{width:100%;height:auto;display:block}.plate-caption{display:flex;justify-content:space-between;font-size:12px;padding:0 26px 24px}.story{background:#e9e7df;color:#242724;padding:100px 0 110px}.article-layout{display:grid;grid-template-columns:240px 1fr;gap:100px}.article-margin{display:flex;flex-direction:column;gap:8px;font-size:14px;color:#72756e;padding-top:10px}.article{max-width:680px}.article h2{font-size:43px;max-width:600px;margin-bottom:38px}.story-lead{font-family:Libre;font-size:23px;line-height:1.75;color:#353b34;margin-bottom:45px}.body-copy p{font-size:21px;line-height:1.8;color:#51564f;margin-bottom:27px}.body-copy blockquote{margin:45px 0 45px -32px;padding:0 0 0 30px;border-left:1px solid #8f9688;font-size:29px;line-height:1.65;color:#30382e;max-width:600px}.body-copy .article-close{color:#262e25;margin-top:45px}.study-note{font-size:13px;color:#7e8378;margin-top:55px;padding-top:18px;border-top:1px solid #c9ccc1}.footer{padding:38px 0;font-size:14px;color:#9d9f9b}.footer .row{display:flex;justify-content:space-between;gap:20px}.footer a{color:#c8cbd0}
/* Challenge diagrams share a paper ground with their reading context. */
.challenge-page{background:#e9e7df;color:#252a29}.challenge-page header{background:#e9e7df;border-color:#c7cbc2;color:#252a29}.challenge-page nav a{color:#71786e}.challenge-page nav a.active,.challenge-page nav a:hover{color:#252a29}.challenge-page .brand svg path:last-child{fill:#e9e7df}.challenge-page p{color:#596158}.page-title{padding:75px 0 68px;display:grid;grid-template-columns:240px 1fr;column-gap:100px}.page-title>.eyebrow{grid-column:1;padding-top:10px}.page-title h1{grid-column:2;max-width:730px;font-size:53px}.page-title>p{grid-column:2;max-width:650px;margin:28px 0 0;font-size:19px}.chapter-nav{grid-column:2;display:flex;gap:28px;flex-wrap:wrap;margin-top:32px;font-size:15px}.chapter-nav a{border-bottom:1px solid #8a9387;padding-bottom:2px}.eyebrow{font-size:14px;color:#747d71;display:block;margin-bottom:18px}.chapter{padding:65px 0 75px;border-top:1px solid #b9c0b3}.chapter-head{display:grid;grid-template-columns:240px 1fr;gap:100px}.chapter-head h2{font-size:37px;margin-bottom:0}.chapter-head>p{font-size:20px;max-width:680px;margin:0}.chapter .eyebrow{font-size:13px;margin-bottom:10px}.viz{position:relative;margin:35px 0 0;padding:0;background:none}.viz-top{display:flex;justify-content:space-between;gap:20px;font-size:12px;color:#7a8278;padding:10px 0;border-bottom:1px solid #cbd0c5}.viz svg{display:block;width:100%;height:auto;overflow:visible}.viz text{font-family:Source,Arial,sans-serif}.controls{display:flex;gap:22px;flex-wrap:wrap;justify-content:center;margin:0 auto 20px}.chip{border:0;border-radius:0;background:none;color:#6a7268;padding:5px 0;font-size:15px;display:inline-flex;align-items:center;gap:8px}.chip:before{content:'';width:11px;height:11px;border:1px solid #a2ac9e}.chip[aria-pressed=true]{color:#273e47}.chip[aria-pressed=true]:before{background:#3b6378;border-color:#3b6378;box-shadow:inset 0 0 0 2px #e9e7df}.caption{color:#566251;max-width:760px;margin:25px auto 10px;font-size:16px;text-align:center;min-height:52px}.legend{display:flex;gap:24px;justify-content:center;flex-wrap:wrap;font-size:13px;color:#63705e;margin:20px 0}.legend i{display:inline-block;width:18px;height:2px;vertical-align:middle;background:#8c7957;margin-right:8px}.legend i.blue{background:#3f6f88}.legend i.dash{background:repeating-linear-gradient(90deg,#7f897d 0 3px,transparent 3px 6px)}.range-wrap{display:grid;grid-template-columns:160px 1fr 100px;align-items:center;gap:25px;max-width:600px;margin:24px auto;font-size:15px;color:#4e5c48}input[type=range]{accent-color:#476c7a;width:100%;cursor:pointer}.figure-note{display:grid;grid-template-columns:240px 1fr;gap:100px;border-top:1px solid #ccd0c6;margin-top:26px;padding-top:16px;font-size:15px}.figure-note span{color:#76806f}.figure-note p{margin:0;max-width:710px;font-size:15px}.challenge-page .study-note{margin:0 0 45px}.challenge-page .footer{border-top:1px solid #bdc4b7;color:#727b6b}.challenge-page .footer a{color:#3b4634}.speed-layout{display:grid;grid-template-columns:1.25fr 1fr;align-items:center;gap:55px}.cost-list{padding:10px 0}.cost-item{padding:16px 0;border-bottom:1px solid #c6ccc0;display:grid;grid-template-columns:25px 1fr;gap:12px}.cost-item span{color:#7d8976;font-size:12px;padding-top:3px}.cost-item h3{margin:0 0 3px;font-size:19px;color:#37442f;font-weight:400}.cost-item p{font-size:15px;margin:0;color:#677360}.sv-label{font-size:16px;fill:#3b493a}.sv-small{font-size:13px;fill:#75806e}.quiet{color:#74816b}
@media(max-width:750px){header{padding:20px 6vw}.brand{font-size:16px;gap:9px}.brand svg{width:20px;height:20px}nav{gap:20px;font-size:14px}.wrap{width:88vw}.hero{padding:55px 0}.hero-layout{grid-template-columns:1fr;gap:45px}.hero-copy{padding:0}.hero-intro{margin-bottom:28px;font-size:14px}.hero h1{font-size:42px}.hero-copy>p:not(.hero-intro){font-size:18px;margin-top:25px}.brand-plate{width:100%;max-width:430px}.brand-plate svg{max-height:360px}.plate-caption{padding:0 20px 17px}.story{padding:50px 0 60px}.article-layout{grid-template-columns:1fr;gap:30px}.article-margin{flex-direction:row;justify-content:space-between;font-size:13px;padding:0}.article h2{font-size:32px;margin-bottom:28px}.story-lead{font-size:20px;line-height:1.7;margin-bottom:30px}.body-copy p{font-size:19px;line-height:1.75}.body-copy blockquote{margin:32px 0;padding-left:18px;font-size:25px}.study-note{margin-top:35px}.footer .row{font-size:13px}.page-title{grid-template-columns:1fr;gap:0;padding:44px 0 45px}.page-title>.eyebrow,.page-title h1,.page-title>p,.chapter-nav{grid-column:1}.page-title h1{font-size:38px}.page-title>p{font-size:18px;margin-top:20px}.chapter-nav{font-size:14px;gap:23px}.chapter{padding:40px 0 45px}.chapter-head{grid-template-columns:1fr;gap:20px}.chapter-head h2{font-size:32px}.chapter-head>p{font-size:18px}.viz{margin-top:25px}.viz-top{font-size:11px;gap:15px}.viz-top span:last-child{text-align:right;max-width:160px}.controls{gap:8px 18px;margin-top:5px;justify-content:flex-start}.chip{font-size:14px}.speed-layout{grid-template-columns:1fr;gap:0}.cost-list{display:grid;grid-template-columns:1fr 1fr;gap:8px 18px;padding:0}.cost-item{gap:6px;grid-template-columns:17px 1fr;padding:12px 0}.cost-item h3{font-size:17px}.cost-item p{font-size:14px}.range-wrap{grid-template-columns:1fr 1fr;gap:8px;padding:0}.range-wrap input{grid-column:1/-1;grid-row:2}.range-wrap output{text-align:right}.caption{font-size:15px;text-align:left;min-height:75px}.figure-note{grid-template-columns:1fr;gap:7px;padding-top:14px;margin-top:20px}.figure-note p{font-size:15px}.horizon-svg{min-height:310px}.insight-svg{min-height:250px}.sv-label{font-size:20px}.sv-small{font-size:16px}.legend{justify-content:flex-start;gap:10px 20px;font-size:12px}.challenge-page .study-note{margin-bottom:30px}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{animation:none!important;transition:none!important}}
/* Full viewport opening; the same cloth image remains behind the reading. */
.curtain-page{background:#0d1013;--scene-blur:0px;--scene-dim:0;--hero-opacity:1;--title-reveal:0}.curtain-stage{position:fixed;inset:-35px;z-index:-1;overflow:hidden;pointer-events:none;background:#0d1013}.curtain-stage canvas{display:block;width:100%;height:100%;filter:blur(var(--scene-blur));transform:scale(1.04)}.curtain-stage:after{content:'';position:absolute;inset:0;background:#0b0e12;opacity:var(--scene-dim)}.curtain-page header{position:fixed;top:0;width:100%;background:transparent;border-bottom:0}.curtain-page .hero{height:100svh;min-height:720px;padding:100px 0 70px;display:flex;align-items:center;text-align:center}.curtain-page .hero-layout{display:block}.curtain-page .hero-copy{max-width:850px;margin:auto;padding:0;opacity:calc(var(--hero-opacity) * var(--title-reveal));transform:translateY(calc((1 - var(--title-reveal)) * 16px))}.curtain-page .hero-intro{margin:0 0 29px;font-size:18px;color:#b2b5b2}.curtain-page .hero h1{font-size:clamp(46px,5.8vw,82px);line-height:1.22;letter-spacing:-.04em}.curtain-page .hero-copy>p:not(.hero-intro){max-width:590px;margin:30px auto 0;font-size:19px;color:#b8bdc1}.curtain-page .hero .textlink{font-size:15px;margin-top:55px;gap:25px;border-bottom:0;color:#b6babd}.replay-opening{position:absolute;bottom:25px;right:5vw;background:none;border:0;border-bottom:1px solid #747d80;padding:3px 0;color:#959da2;font-size:12px;opacity:var(--hero-opacity)}.curtain-page .story{background:transparent;color:#e6e5de;position:relative;padding:145px 0 120px}.curtain-page .article-margin{color:#9ca6ab}.curtain-page .article h2{color:#e5e5df}.curtain-page .story-lead{color:#d0d4d2}.curtain-page .body-copy p{color:#b8c0c4}.curtain-page .body-copy blockquote{color:#e2e4de;border-color:#687a7c}.curtain-page .body-copy .article-close{color:#dde0da}.curtain-page .study-note{color:#8b979e;border-color:#53606b}.curtain-page .footer{background:transparent;border-top:1px solid #ffffff15}.curtain-page header{background:linear-gradient(#0d101380,transparent)}@media(max-width:750px){.curtain-page .hero{height:100svh;min-height:740px;padding:110px 0 70px}.curtain-page .hero h1{font-size:43px}.curtain-page .hero-copy>p:not(.hero-intro){font-size:18px;max-width:330px}.curtain-page .hero-intro{font-size:16px;margin-bottom:28px}.curtain-page .story{padding:85px 0 75px}.curtain-page .hero .textlink{margin-top:42px}.curtain-page .article h2{font-size:32px}.replay-opening{right:6vw}}

.curtain-page .hero-copy{transform:none}
/* Challenge revisions: erosion in time, and an accumulating knowledge structure. */
.motion-controls{display:flex;justify-content:center;gap:24px;margin:16px 0 8px;font-size:14px;color:#51645a}.motion-controls button{padding:3px 0;background:none;border:0;border-bottom:1px solid #a7b1a1;color:inherit}.motion-controls button:disabled{cursor:default;opacity:.65;border-color:transparent}.cost-item{transition:opacity .3s,border-color .3s}.cost-item.is-active{border-bottom-color:#4b7488}.cost-item.is-active h3,.cost-item.is-active>span{color:#245a76}.edge-retained{font-size:18px;fill:#f3f0e5}.legend i.tower-key{height:10px;width:10px;background:#f8f6f0;border:1px solid #81928a}.insight-svg{overflow:hidden!important;aspect-ratio:1100/560}
@media(max-width:750px){.motion-controls{justify-content:flex-start;font-size:14px}.insight-svg{aspect-ratio:660/560;min-height:0}.insight-svg .sv-label{font-size:26px}.insight-svg .sv-small{font-size:23px}.speed-layout .sv-label{font-size:21px}.speed-layout .sv-small{font-size:22px}.speed-layout .edge-retained{font-size:21px}}