:root{color-scheme:dark;--bg:#070b10;--surface:#0d141c;--ink:#ece9df;--muted:#a9b7c3;--rule:#2c3740;--amber:#edb361;--cyan:#93d9f0}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.7 system-ui,-apple-system,sans-serif}a{color:inherit;text-decoration:none}a:hover{color:var(--amber)}a:focus-visible,button:focus-visible,textarea:focus-visible{outline:2px solid var(--cyan);outline-offset:5px}button,textarea{font:inherit}button,.button{border:1px solid #66737d;background:transparent;color:var(--ink);padding:12px 22px;border-radius:6px;cursor:pointer;font-size:14px;line-height:1.4;display:inline-flex;align-items:center;justify-content:center;gap:12px;text-decoration:none}button:hover,.button:hover{border-color:var(--amber);color:var(--amber)}.primary{background:var(--amber);border-color:var(--amber);color:#15100a}.primary:hover{background:#ffca80;color:#15100a}header,main,footer{max-width:1480px;margin:auto;padding-left:48px;padding-right:48px}header{height:96px;display:flex;align-items:center;justify-content:space-between;gap:24px}.brand{font-family:Georgia,serif;letter-spacing:.34em;font-size:26px;color:#f4f0e5}header nav{display:flex;gap:30px;font-size:14px}header nav .active{color:var(--amber)}.header-actions{display:flex;align-items:center;gap:25px}.locale{font-size:13px}.compact{padding:10px 18px}.hero{min-height:505px;position:relative;background:url('/epoch/assets/towers.webp')right center/cover no-repeat;display:flex;align-items:center;margin:0 -10px;padding:30px 10px}.hero-copy{position:relative;width:58%;padding-bottom:35px}.hero h1{font:500 clamp(52px,6vw,86px)/1.03 Georgia,serif;letter-spacing:-.035em;max-width:600px;margin:15px 0 22px}.hero-sub{font:25px/1.45 Georgia,serif;max-width:530px;margin:0 0 28px}.actions{display:flex;gap:15px;flex-wrap:wrap}.method-row{display:grid;grid-template-columns:1fr 1.2fr 1fr 1.2fr;align-items:center;gap:24px;border-top:1px solid var(--rule);border-bottom:1px solid var(--rule);padding:34px 0}.method-row>a{font:20px Georgia,serif;letter-spacing:.12em}.method-row p{margin:0;font:20px/1.5 Georgia,serif;color:#ccd5db}.scene-section{padding:26px 0;border-bottom:1px solid var(--rule)}h2{font:400 34px/1.2 Georgia,serif;letter-spacing:-.02em;margin:0 0 24px}.scene-tabs{display:grid;grid-template-columns:repeat(6,1fr);gap:12px}.scene-tabs button{flex-direction:column;align-items:flex-start;gap:15px;padding:20px 18px;min-height:95px;background:var(--surface);text-align:left}.scene-number{color:var(--muted);font:12px ui-monospace,monospace}.scene-tabs button[aria-pressed=true]{border-color:var(--amber);background:#1c1b18;color:var(--amber)}.scene-description{display:flex;justify-content:space-between;align-items:center;gap:20px;margin-top:10px}.scene-description p{color:var(--muted);margin:12px 0;max-width:700px}.scene-description a{font-size:14px;color:var(--cyan)}.caption{font-size:12px;color:var(--muted);line-height:1.6}.learning-band{display:flex;align-items:center;justify-content:space-between;gap:40px;padding:38px 0;border-bottom:1px solid var(--rule)}.learning-band h2{max-width:420px;margin:0}.learning-band>div{display:flex;gap:35px;align-items:center}.learning-band p{color:var(--muted);font-size:16px}.section{padding:46px 0}.section-heading{display:flex;align-items:baseline;justify-content:space-between;gap:20px}.section-heading>a{font-size:14px;color:var(--cyan)}.reading-list>a{display:grid;grid-template-columns:1fr 1fr 25px;gap:24px;padding:24px 0;border-bottom:1px solid var(--rule);align-items:center}.reading-list span{font:24px/1.3 Georgia,serif}.reading-list small{font-size:14px;line-height:1.7;color:var(--muted)}.reading-list b{font-weight:400;color:var(--amber)}.page-intro,.article-hero{padding:45px 0 42px;max-width:1000px}.page-intro h1,.article-hero h1{font:400 clamp(38px,4.5vw,65px)/1.1 Georgia,serif;letter-spacing:-.025em;margin:0 0 24px}.lead{font:22px/1.5 Georgia,serif;color:#c2cdd5;max-width:800px}.article-hero button{margin-top:12px}.article-layout{display:grid;grid-template-columns:250px minmax(0,820px);gap:70px;padding:28px 0 65px;border-top:1px solid var(--rule)}.toc{position:sticky;top:24px;align-self:start;display:flex;flex-direction:column;gap:14px;font-size:14px;line-height:1.5;color:var(--muted)}.toc a:last-child{margin-top:20px;color:var(--cyan)}.prose{min-width:0}.prose section{margin-bottom:42px;scroll-margin-top:20px}.prose p{font-size:18px;line-height:1.9;color:#c5cfd6}.prose h2{font-size:31px}.prose .sources{padding-top:25px;border-top:1px solid var(--rule)}.sources p{font-size:15px}.sources a{color:var(--cyan)}.offer{padding:25px 0 30px;border-top:1px solid #745735;border-bottom:1px solid #745735;margin:45px 0}.offer p{font-size:16px}.prose .reading-list>a{grid-template-columns:1fr 30px}.prose .reading-list small{grid-column:1}.prose .reading-list b{grid-column:2;grid-row:1/3}.atlas-art{margin:0 0 25px}.atlas-art img{display:block;width:100%;height:auto;border:1px solid var(--rule)}figcaption{color:var(--muted);font-size:13px;margin-top:10px}.notice{border-left:2px solid var(--amber);padding:12px 20px;color:var(--muted);font-size:14px;max-width:850px}.training-layout{display:grid;grid-template-columns:1.1fr 1fr;gap:70px;padding-bottom:65px}.question{border:0;border-top:1px solid var(--rule);padding:25px 0;margin:20px 0}.question legend{font:23px/1.5 Georgia,serif;padding-top:20px}.question legend span{font:12px ui-monospace,monospace;color:var(--amber);display:block;margin-bottom:10px}.answers{display:grid;gap:12px}.answers button{text-align:left;justify-content:flex-start;padding:16px;font-size:15px}.answers button[aria-pressed=true]{border-color:var(--amber)}.feedback{color:var(--cyan);font-size:15px;min-height:24px}.practice-aside{background:var(--surface);padding:28px;align-self:start;border-top:1px solid var(--amber)}.practice-aside>p{font-size:14px;color:var(--muted)}label{display:block;font-size:14px;margin:22px 0}textarea{display:block;resize:vertical;width:100%;background:var(--bg);border:1px solid #52616b;color:var(--ink);padding:12px;margin-top:8px;border-radius:4px}pre{white-space:pre-wrap;overflow-wrap:anywhere;font:12px/1.6 ui-monospace,monospace;max-width:100%;color:var(--muted)}[hidden]{display:none!important}#progress{color:var(--amber)}footer{padding-top:38px;padding-bottom:38px;border-top:1px solid var(--rule);margin-top:20px}footer p{color:var(--muted)}footer>div{display:flex;gap:24px;flex-wrap:wrap;font-size:14px}footer small{display:block;color:var(--muted);margin-top:28px;font-size:12px}.skip{position:absolute;top:-100px}.skip:focus{top:8px;left:8px;background:var(--bg);padding:10px;z-index:10}@media(min-width:1500px){.hero{min-height:540px}}@media(max-width:1100px){header,main,footer{padding-left:28px;padding-right:28px}header nav{gap:18px}.hero h1{font-size:67px}.hero-copy{width:65%}.method-row{grid-template-columns:1fr 1.2fr;gap:18px}.learning-band>div{flex-direction:column;gap:8px;align-items:flex-start}.article-layout{grid-template-columns:190px 1fr;gap:35px}.scene-tabs button{padding:15px 10px}.training-layout{gap:35px}}@media(max-width:760px){header{height:auto;min-height:90px;flex-wrap:wrap;padding-top:20px;padding-bottom:18px;gap:18px}.brand{font-size:22px}header nav{order:3;width:100%;justify-content:space-between;font-size:12px;gap:12px}.header-actions{gap:18px}.compact{font-size:12px;padding:8px 12px}header,main,footer{padding-left:22px;padding-right:22px}.hero{min-height:670px;align-items:flex-end;background-position:74% top;background-size:auto 340px;padding-top:310px}.hero-copy{width:100%;padding-bottom:32px}.hero h1{font-size:53px;max-width:440px;margin-top:0}.hero-sub{font-size:23px;max-width:350px}.actions{gap:12px}.actions .button{font-size:13px;padding:12px 16px}.method-row{grid-template-columns:1fr;gap:12px;padding:25px 0}.method-row p{font-size:19px}.method-row a:nth-of-type(2){padding-top:15px}.scene-tabs{grid-template-columns:repeat(3,1fr);gap:8px}.scene-tabs button{font-size:13px;min-height:85px}.scene-description{align-items:flex-start;flex-direction:column;gap:0}.scene-description p{font-size:15px}.learning-band{flex-direction:column;align-items:flex-start;gap:15px}.learning-band>div{gap:12px}h2{font-size:30px}.section-heading{align-items:flex-start;flex-direction:column;gap:0}.reading-list>a{grid-template-columns:1fr 22px;gap:10px}.reading-list small{grid-column:1}.reading-list b{grid-column:2;grid-row:1/3}.reading-list span{font-size:23px}.page-intro,.article-hero{padding:35px 0}.page-intro h1,.article-hero h1{font-size:43px}.article-layout{display:block}.toc{position:static;border-bottom:1px solid var(--rule);padding-bottom:24px;margin-bottom:32px}.prose p{font-size:17px}.prose h2{font-size:29px}.training-layout{grid-template-columns:1fr;gap:38px}.practice-aside{padding:22px}.lead{font-size:21px}.question legend{font-size:22px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;animation:none!important;transition:none!important}}

/* Production scene assets preserve native headings and controls. */
body[data-visual=neurons] .hero{background-image:url('/epoch/assets/scene-neurons.webp')}
body[data-visual=atlas] .hero{background-image:url('/epoch/assets/scene-atlas.webp')}
body[data-visual=keywords] .hero{background-image:url('/epoch/assets/scene-keywords.webp')}
body[data-visual=city] .hero{background-image:url('/epoch/assets/scene-city.webp')}
body[data-visual=orbits] .hero{background-image:url('/epoch/assets/scene-orbits.webp')}
.scene-tabs button{position:relative;padding:0 0 12px;gap:8px;align-items:stretch;text-align:center;overflow:hidden}
.scene-tabs button img{width:100%;height:105px;object-fit:cover;object-position:85% center}
.scene-number{position:absolute;left:8px;top:8px;background:#070b10bf;padding:1px 5px;border-radius:2px}
.scene-label{padding:0 7px}
.article-hero{max-width:none;position:relative;padding-right:37%;min-height:360px}
.article-scene{position:absolute;right:0;top:25px;width:34%;height:300px;object-fit:cover;object-position:80% center}
@media(max-width:760px){.scene-tabs button img{height:75px}.scene-label{font-size:12px}.article-hero{padding-right:0;padding-top:230px}.article-scene{top:15px;width:100%;height:190px;object-position:80% center}}

button:disabled{cursor:wait;opacity:.7}