@font-face{font-family:Manrope;src:url('assets/fonts/manrope-latin-wght-normal.woff2') format('woff2');font-weight:200 800;font-display:swap}
@font-face{font-family:Newsreader;src:url('assets/fonts/newsreader-latin-wght-normal.woff2') format('woff2');font-weight:200 800;font-display:swap}
@font-face{font-family:Newsreader;src:url('assets/fonts/newsreader-latin-wght-italic.woff2') format('woff2');font-weight:200 800;font-style:italic;font-display:swap}
:root{--paper:#fffefa;--wash:#f3f3ef;--figure-bg:#f1f4f1;--figure-tint:#e2ece7;--ink:#242931;--muted:#646b72;--line:#dcdfdb;--geometry:#007c78;--curvature:#7951bb;--transport:#275dc5;--matter:#a25e00;--observer:#bb365d;--teal:var(--geometry);--orange:var(--observer);--body-size:1.34rem;--sidebar-width:246px;--soft-shadow:0 12px 36px #29322f06;color-scheme:light;scroll-behavior:smooth;scroll-padding-top:90px}
html[data-theme=dark]{--paper:#111722;--wash:#18212f;--figure-bg:#192331;--figure-tint:#27394a;--ink:#ebedf0;--muted:#acb4c1;--line:#323d4d;--geometry:#64d9c9;--curvature:#bd9cff;--transport:#8bb5ff;--matter:#f3c16e;--observer:#ff99b4;--soft-shadow:0 12px 40px #0002;color-scheme:dark}
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.equation{overflow-x:auto;overflow-y:hidden;max-width:100%;padding:25px 22px;margin:30px 0;border:1px solid var(--line);border-radius:12px;background:var(--wash);color:var(--ink);scrollbar-width:thin;box-shadow:var(--soft-shadow);font-size:1.42rem}.equation>.katex-display{margin:.4em 0}.equation .katex-display{width:max-content;min-width:100%}.katex-display>.katex{white-space:nowrap}.prose>.equation{font-size:1.42rem}.prose .katex{font-size:1.04em}.katex .katex-mathml{contain:strict;clip-path:inset(50%);position:fixed;left:0;top:0}.math-geometry{color:var(--geometry)}.math-curvature{color:var(--curvature)}.math-transport{color:var(--transport)}.math-matter{color:var(--matter)}.math-observer{color:var(--observer)}.table-wrap{overflow-x:auto;margin:28px 0;border:1px solid var(--line);border-radius:10px;font-family:Manrope,Arial,sans-serif;font-size:12px;line-height:1.8}table{border-collapse:collapse;width:100%;min-width:460px}th,td{text-align:left;vertical-align:top;padding:15px 18px;border-bottom:1px solid var(--line)}th{background:var(--wash);font-weight:750}tr:last-child td{border-bottom:0}.prose hr{border:0;border-top:1px solid var(--line);margin:52px 0}.section-rail{position:sticky;top:118px;align-self:start;max-height:calc(100vh - 150px);overflow:auto;scrollbar-width:thin;margin-top:76px}.section-rail nav{margin-top:19px;border-left:1px solid var(--line)}.section-rail nav a{display:block;font-size:10px;line-height:1.6;color:var(--muted);text-decoration:none;padding:9px 0 9px 15px}.section-rail nav a:hover,.section-rail nav a.current{color:var(--geometry);border-left:2px solid var(--geometry);margin-left:-1px}.rail-top{display:block;font-size:10px;text-decoration:none;margin:26px 16px}
.color-key{border:1px solid var(--line);border-radius:12px;margin:28px 0 42px;overflow:hidden;background:var(--paper);font-family:Manrope,Arial,sans-serif}.color-key summary{display:flex;align-items:center;gap:12px;cursor:pointer;padding:18px 20px;list-style:none;font-size:12px;font-weight:700}.color-key summary::-webkit-details-marker{display:none}.color-key summary:after{content:'+';font-size:20px;font-weight:400;margin-left:auto}.color-key[open] summary:after{content:'−'}.key-hint{font-size:10px;font-weight:500;color:var(--muted);margin-left:auto}.spectrum{display:flex;gap:3px}.spectrum i{width:5px;height:17px;border-radius:5px;background:var(--geometry)}.spectrum i:nth-child(2){background:var(--transport)}.spectrum i:nth-child(3){background:var(--curvature)}.spectrum i:nth-child(4){background:var(--matter)}.spectrum i:nth-child(5){background:var(--observer)}.color-roles{display:grid;grid-template-columns:repeat(5,1fr);padding:22px;gap:18px;border-top:1px solid var(--line)}.role-example{display:block;font-size:1.35rem;margin-bottom:17px}.color-role strong{display:block;font-size:10px;line-height:1.55}.color-role p{font-size:10px;color:var(--muted);line-height:1.8;margin:8px 0 0}.key-note{font-size:10px;line-height:1.8;color:var(--muted);margin:0;padding:0 22px 22px}.key-note .katex{font-size:1.2em}
.diagram{margin:42px 0}.figure-surface{position:relative;border:1px solid var(--line);border-radius:16px;overflow:hidden;background:var(--figure-bg)}.gr-figure{display:block;width:100%;height:auto}.figure-zoom{position:absolute;right:12px;top:12px;border:1px solid var(--line);display:grid;place-items:center;width:34px;height:34px;border-radius:9px;color:var(--muted);background:var(--paper);opacity:.6;transition:opacity .15s}.figure-zoom .hugeicon{width:18px;height:18px}.figure-surface:hover .figure-zoom,.figure-zoom:focus{opacity:1}.diagram figcaption{display:flex;gap:14px;font-family:Manrope,Arial,sans-serif;font-size:11px;line-height:1.85;color:var(--muted);margin:16px 2px 0}.diagram figcaption strong{color:var(--ink);font-weight:700}.figure-number{white-space:nowrap;font-size:10px;letter-spacing:1px;color:var(--curvature);font-weight:800;padding-top:1px}.takeaway{padding:35px;background:var(--wash);border-radius:18px;margin:56px 0;border:1px solid var(--line)}.takeaway h2{margin:16px 0;font-size:2.4rem}.takeaway>p{font-family:Newsreader,Georgia,serif;font-size:1.35rem;line-height:1.7}.checkpoint{margin:25px 0;border:1px solid var(--line);border-radius:10px;font-family:Manrope,Arial,sans-serif;font-size:13px;line-height:1.8;background:var(--paper)}.checkpoint summary{cursor:pointer;padding:19px 22px;font-weight:650}.checkpoint[open] summary{border-bottom:1px solid var(--line);color:var(--geometry)}.checkpoint>p,.checkpoint>.equation{margin:20px 22px}.page-turn{display:grid;grid-template-columns:1fr 1fr;gap:34px;border-top:1px solid var(--line);padding:32px 0 70px}.page-turn a{font-size:14px;text-decoration:none}.page-turn a:last-child{text-align:right}.page-turn small{display:block;font-size:9px;font-weight:750;letter-spacing:1.5px;color:var(--muted);margin-bottom:10px}.site-footer{border-top:1px solid var(--line);padding:32px 42px;font-size:10px;color:var(--muted);display:flex;gap:18px;flex-wrap:wrap;justify-content:space-between}
.cover{margin:48px 0 0;display:grid;grid-template-columns:1.06fr 1fr;gap:25px 0;position:relative}.cover-copy{padding:22px 0 15px;position:relative;z-index:2}.cover h1{font-size:clamp(4.8rem,7vw,8rem);line-height:.98;margin:32px 0 24px;letter-spacing:-.06em}.cover h1 em{color:var(--curvature)}.cover-subtitle{font-family:Newsreader,Georgia,serif;font-size:1.9rem;line-height:1.2;letter-spacing:-.025em;margin:25px 0;color:var(--ink)}.cover-intro{font-size:12px;line-height:1.9;color:var(--muted);margin:24px 0}.cover-prereq{font-size:9px;letter-spacing:.3px;color:var(--muted);margin-top:18px}.start-link{display:inline-flex;align-items:center;gap:28px;background:var(--ink);color:var(--paper);text-decoration:none;font-weight:650;padding:15px 21px;border-radius:11px;font-size:12px;box-shadow:var(--soft-shadow)}.start-link:hover{background:var(--curvature);color:var(--paper)}.cover-model{min-width:0;align-self:center;position:relative;border-radius:50%;background:radial-gradient(ellipse at 50% 44%,color-mix(in srgb,var(--curvature) 11%,transparent),transparent 68%)}.cover-model>p{font-size:10px;line-height:1.7;color:var(--muted);text-align:center;margin:12px 0}.cover-equation{grid-column:1/-1;overflow-x:auto;padding:30px 0 24px;border-top:1px solid var(--line);border-bottom:1px solid var(--line);font-size:1.28rem;scrollbar-width:thin}.cover-equation>.eyebrow{font-size:8px;justify-content:center;margin-bottom:27px;color:var(--muted)}.cover-equation .katex-display{margin:10px 0;width:max-content;min-width:100%}.welcome{padding:80px 0 48px;max-width:840px}.welcome h2{font-size:3.2rem;margin:23px 0;line-height:1.1}.welcome>p{font-family:Newsreader,Georgia,serif;font-size:1.5rem;line-height:1.65;color:var(--muted);max-width:760px}.book-facts{display:flex;gap:60px;margin:38px 0}.book-facts span{font-size:11px;color:var(--muted)}.book-facts strong{display:block;font-family:Newsreader,Georgia,serif;color:var(--ink);font-size:2.9rem;font-weight:400;line-height:1.35}.feature-links{display:flex;gap:24px;flex-wrap:wrap;margin:40px 0 0}.feature-links a{display:flex;align-items:center;gap:10px;font-size:11px;text-decoration:none}.feature-links .hugeicon:last-child{width:16px}.book-contents{padding:32px 0 75px}.section-heading{display:flex;justify-content:space-between;gap:24px;align-items:center;margin:30px 0}.section-heading h2{margin:12px 0;font-size:2.8rem}.section-heading>.hugeicon{width:36px;height:36px;color:var(--curvature)}.section-heading>span{font-size:10px;color:var(--muted)}.contents-group{margin:38px 0 52px}.contents-group>.eyebrow{margin-bottom:20px}.chapter-card{display:flex;align-items:center;gap:28px;text-decoration:none;border-top:1px solid var(--line);padding:25px 5px;color:var(--ink);transition:padding .18s,background .18s}.chapter-card:last-child{border-bottom:1px solid var(--line)}.chapter-card:hover{padding-left:14px;background:var(--wash);color:var(--curvature)}.card-number{font-family:Newsreader,Georgia,serif;font-size:2rem;color:var(--muted);opacity:.7;min-width:42px}.chapter-card h3{font-size:1.14rem;margin:0 0 8px;letter-spacing:-.025em}.chapter-card p{font-size:11px;line-height:1.7;margin:0;color:var(--muted)}.card-arrow{margin-left:auto;color:var(--curvature)}.appendix-links{display:grid;gap:15px;font-size:12px}
.spacetime-lab{margin:46px 0 50px;border:1px solid var(--line);border-radius:22px;background:var(--figure-bg);overflow:hidden;box-shadow:var(--soft-shadow);position:relative}.scene-heading{padding:30px 32px 0}.scene-heading h2{font-size:2.5rem;margin:18px 0 16px;max-width:680px}.scene-heading>p{font-size:12px;line-height:1.85;max-width:620px;color:var(--muted);margin-bottom:0}.scene-stage{height:450px;position:relative;overflow:hidden;background:radial-gradient(ellipse at center,color-mix(in srgb,var(--geometry) 7%,transparent),transparent 70%);isolation:isolate}.scene-stage>canvas{display:block;position:absolute;inset:0;width:100%;height:100%;touch-action:none}.scene-labels{position:absolute;inset:0;pointer-events:none;overflow:hidden}.scene-label{font-size:15px;background:color-mix(in srgb,var(--figure-bg) 85%,transparent);padding:2px 6px;border-radius:5px;white-space:nowrap;pointer-events:none}.scene-fallback{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;flex-direction:column;padding:20px}.scene-fallback img{display:block;width:100%;max-height:85%;object-fit:contain}.scene-fallback span{font-size:11px;padding:12px;color:var(--muted)}[data-ready=true] .scene-fallback{display:none}[data-ready=fallback] canvas,[data-ready=fallback] .scene-labels{display:none}.scene-toolbar{display:flex;align-items:center;justify-content:space-between;gap:12px;margin:0 30px;padding:13px 0;border-top:1px solid var(--line);font-size:10px;color:var(--muted)}.scene-toolbar>span{display:flex;align-items:center;gap:8px}.scene-toolbar .hugeicon{width:17px;height:17px}.scene-toolbar>div{display:flex;gap:5px}.scene-toolbar button{display:grid;place-items:center;width:33px;height:31px;border:1px solid var(--line);border-radius:7px;background:var(--paper)}.scene-toolbar button:hover{color:var(--curvature)}.scene-controls{padding:16px 30px 20px}.scene-controls label{display:block;font-size:11px;font-weight:700}.scene-controls output{float:right;color:var(--transport);font-size:11px}.scene-controls input[type=range]{display:block;width:100%;accent-color:var(--transport);margin:17px 0 8px;height:22px;cursor:pointer}.range-limits{display:flex;justify-content:space-between;gap:15px;font-size:9px;color:var(--muted)}.scene-equation.equation{border-width:1px 0;border-radius:0;background:color-mix(in srgb,var(--paper) 60%,transparent);box-shadow:none;margin:0;padding:24px 20px;font-size:1.06rem}.scene-note{font-size:10px;line-height:1.9;padding:21px 30px;margin:0;color:var(--muted)}.scene-note strong{color:var(--ink)}.hero-scene.spacetime-lab{background:none;box-shadow:none;border:0;margin:0;overflow:visible}.hero-scene .scene-heading{padding:0 20px}.hero-scene .scene-heading .eyebrow{justify-content:center;font-size:8px;color:var(--muted)}.hero-scene .scene-stage{height:365px;background:none}.hero-scene .scene-toolbar{margin:0 15px;font-size:9px;border:0;padding:0}.hero-scene .scene-toolbar>span .hugeicon{display:none}.hero-scene .scene-controls{padding:16px 15px 4px}.hero-scene .scene-controls label{font-size:9px}.hero-scene .scene-controls output{font-size:9px}.hero-scene .range-limits{font-size:8px}.hero-scene .scene-label{background:var(--paper)}
.atlas{max-width:none}.atlas .chapter-header{padding-top:65px}.atlas h1{font-size:clamp(4rem,6vw,6.5rem)}.atlas>.spacetime-lab .scene-stage{height:520px}.atlas-labs{margin:75px 0}.lab-directory{display:grid;grid-template-columns:repeat(2,1fr);gap:18px}.lab-directory>a{display:flex;flex-direction:column;text-decoration:none;color:var(--ink);border:1px solid var(--line);border-radius:15px;padding:26px;background:linear-gradient(140deg,color-mix(in srgb,var(--curvature) 5%,var(--paper)),var(--paper));transition:border-color .15s,transform .15s}.lab-directory>a:nth-child(3n){background:linear-gradient(140deg,color-mix(in srgb,var(--geometry) 7%,var(--paper)),var(--paper))}.lab-directory>a:nth-child(3n+2){background:linear-gradient(140deg,color-mix(in srgb,var(--observer) 5%,var(--paper)),var(--paper))}.lab-directory>a:hover{border-color:var(--curvature);transform:translateY(-3px)}.lab-card-top{display:flex;justify-content:space-between;align-items:center;font-size:9px;letter-spacing:1.8px;color:var(--curvature)}.lab-card-top .hugeicon{width:19px;height:19px}.lab-directory h3{font-family:Newsreader,Georgia,serif;font-size:1.9rem;line-height:1.18;margin:28px 0 14px;font-weight:450}.lab-directory p{font-size:11px;color:var(--muted);line-height:1.8;margin:0 0 27px}.lab-card-bottom{display:flex;gap:8px;align-items:center;margin-top:auto;font-size:9px;color:var(--muted)}.lab-card-bottom .hugeicon{width:15px;height:15px}.atlas-vectors{padding-bottom:65px}.atlas-filters{display:flex;flex-wrap:wrap;gap:9px;margin:26px 0}.atlas-filters button{border:1px solid var(--line);background:var(--paper);padding:10px 14px;border-radius:25px;font-size:10px}.atlas-filters button.active{background:var(--ink);border-color:var(--ink);color:var(--paper)}.atlas-count{font-size:10px;color:var(--muted)}.atlas-grid{display:grid;grid-template-columns:1fr 1fr;gap:32px 22px}.atlas-item{min-width:0}.atlas-item[hidden]{display:none}.atlas-item .diagram{margin:0 0 13px}.atlas-item .diagram figcaption{font-size:10px;line-height:1.8;gap:10px}.atlas-back{display:flex;align-items:center;gap:10px;font-size:10px;text-decoration:none;margin-left:35px}.atlas-back .hugeicon{width:16px;height:16px}.history-grid{display:grid;grid-template-columns:1fr 1fr;gap:24px;margin:40px 0}.history-grid figure{margin:0}.history-grid img{width:100%;height:340px;object-fit:contain;background:var(--wash);border:1px solid var(--line);border-radius:12px;padding:12px}.history-grid figcaption{font-family:Manrope,Arial,sans-serif;font-size:10px;line-height:1.8;margin-top:13px}.lab{margin:48px 0;border:1px solid var(--line);background:var(--wash);border-radius:18px;padding:32px}.lab h3{font-family:Newsreader,Georgia,serif;font-size:2.2rem;margin:17px 0;font-weight:450}.lab p{font-size:12px;color:var(--muted);line-height:1.9}.lab label{display:block;font-size:12px;font-weight:700;margin-top:25px}.lab output{float:right;color:var(--observer);font-variant-numeric:tabular-nums}.lab input[type=range]{width:100%;margin:20px 0;accent-color:var(--observer);height:24px}.lab-results{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin:20px 0}.lab-results small{display:block;font-size:10px;color:var(--muted)}.lab-results strong{display:block;font-size:1.1rem;color:var(--observer);margin-top:8px}.lab .lab-note{font-size:11px;border-top:1px solid var(--line);padding-top:20px;overflow-x:auto}.clock-bars>div{margin:18px 0}.clock-bars span{font-size:10px;display:block;margin-bottom:7px}.bar{height:38px;padding:7px 11px;white-space:nowrap;border-radius:5px;font-size:12px;min-width:95px}.home{background:var(--line);color:var(--ink)}.travel{background:var(--observer);color:var(--paper)}#wave-ring{display:block;max-height:280px;width:100%}dialog{border:1px solid var(--line);border-radius:18px;background:var(--paper);color:var(--ink);width:min(750px,calc(100vw - 30px));padding:28px;max-height:85vh;box-shadow:0 30px 150px #0005}dialog::backdrop{background:#091220b8;backdrop-filter:blur(8px)}.search-header{display:flex;align-items:center;justify-content:space-between;gap:15px}.search-header h2{margin:0 0 18px;font-size:2.1rem}dialog label{font-size:12px}dialog input{display:block;width:100%;padding:15px;background:var(--wash);color:var(--ink);border:1px solid var(--line);border-radius:9px;margin-top:9px}#search-status{font-size:11px;color:var(--muted)}#search-results a{display:block;text-decoration:none;padding:18px 0;border-top:1px solid var(--line);font-size:13px}#search-results small{display:block;color:var(--muted);margin-top:7px;line-height:1.75;font-size:11px}#figure-dialog{width:min(1440px,calc(100vw - 28px))}.figure-instruction{font-size:11px;color:var(--muted)}#figure-detail{overflow:auto;max-height:66vh;border:1px solid var(--line);border-radius:12px;background:var(--figure-bg)}#figure-detail>.gr-figure{min-width:1000px;width:100%;height:auto}.large-type{--body-size:1.56rem}
@media(min-width:1650px){.reading-layout{gap:50px;padding:0 55px}.topbar{padding:0 55px}}
@media(max-width:1350px){:root{--sidebar-width:226px}.reading-layout{display:block;padding:0 38px}.section-rail{display:none}.topbar{padding:0 38px}.cover h1{font-size:6.1rem}.cover-model .scene-stage{height:320px}.color-roles{gap:12px}}
@media(max-width:1000px){:root{--sidebar-width:206px}.sidebar{padding:30px 9px}.brand{font-size:9px;gap:8px}.brand small{font-size:10px}.sidebar nav>a{font-size:11px;padding:9px}.nav-label{font-size:8px}.reading-layout{padding:0 28px}.topbar{padding:0 28px}.cover{grid-template-columns:1fr}.cover h1{font-size:6.5rem}.cover-model{max-width:520px;width:100%;margin:auto}.cover-model .scene-stage{height:360px}.cover-equation{font-size:1.12rem}.color-roles{grid-template-columns:repeat(3,1fr);row-gap:25px}.key-hint{display:none}.lab-directory{gap:14px}.lab-directory>a{padding:22px}.atlas-grid{grid-template-columns:1fr}.scene-heading h2{font-size:2.2rem}.lab-results{grid-template-columns:1fr}.scene-stage{height:390px}}
@media(max-width:800px){:root{--sidebar-width:0px}.sidebar{visibility:hidden;transform:translateX(-100%);width:285px;padding:30px 18px;transition:transform .18s}.sidebar.open{visibility:visible;transform:translateX(0);box-shadow:30px 0 90px #0005}.sidebar nav>a{font-size:12px;padding:10px}.brand{font-size:11px}.brand small{font-size:12px}.nav-label{font-size:9px}.page{margin-left:0}.topbar{height:64px;padding:0 22px;gap:8px}.top-title{display:none}#menu-button{display:flex}.reading-layout{padding:0 26px}.chapter-header{padding-top:38px}.breadcrumb{margin-bottom:38px}.chapter-header h1{font-size:4.2rem}.cover{grid-template-columns:1fr 1fr;margin-top:32px}.cover h1{font-size:5.5rem}.cover-model .scene-stage{height:300px}.cover-subtitle{font-size:1.7rem}.cover-model .scene-toolbar>span{font-size:8px}.cover-model .scene-controls label{font-size:8px}.cover-model .scene-controls output{float:none;display:block;margin-top:6px}.cover-equation{font-size:1.1rem}.welcome{padding-top:60px}.welcome h2{font-size:2.9rem}.book-facts{gap:40px}.site-footer{padding:30px 26px}.scene-stage{height:420px}.atlas>.spacetime-lab .scene-stage{height:460px}.atlas-grid{grid-template-columns:1fr 1fr}}
@media(max-width:600px){.reading-layout{padding:0 20px}.topbar{padding:0 15px}.reading-tools{gap:4px}#search-button{border:0;padding:9px;margin:0}#search-button span{display:none}.text-button{padding:9px}.cover{grid-template-columns:1fr;margin-top:24px;gap:10px}.cover-copy{padding-top:12px}.cover h1{font-size:clamp(4.8rem,17vw,6.6rem);margin:28px 0 20px}.cover-subtitle{font-size:1.9rem}.cover-model{max-width:420px;margin:5px auto 12px}.cover-model .scene-stage{height:330px}.cover-model .scene-controls output{float:right;margin:0}.cover-model .scene-controls label{font-size:10px}.cover-model .scene-toolbar>span{font-size:9px}.cover-equation{font-size:1.08rem;padding:28px 0}.cover-equation>.eyebrow{font-size:7px;justify-content:flex-start}.cover-equation .katex-display>.katex{display:inline-block;text-align:left}.chapter-header h1,.atlas h1{font-size:3.5rem}.chapter-deck{font-size:1.45rem}.chapter-guide{grid-template-columns:1fr;gap:20px}.chapter-payoff{grid-column:auto}.prose{font-size:1.27rem;line-height:1.78}.large-type .prose{font-size:1.5rem}.prose h3{font-size:1.25rem}.equation,.prose>.equation{font-size:1.17rem;padding:23px 17px;border-radius:10px}.color-key summary{font-size:11px;padding:17px}.color-roles{grid-template-columns:1fr 1fr;padding:20px;gap:24px}.role-example{margin-bottom:10px}.key-note{padding:0 20px 20px}.color-key{margin-bottom:30px}.diagram{margin:32px 0}.figure-surface{border-radius:12px}.figure-zoom{right:8px;top:8px;width:30px;height:30px}.diagram figcaption{font-size:10px;gap:10px}.takeaway,.lab{padding:24px}.takeaway h2{font-size:2.1rem}.page-turn{gap:24px}.page-turn a{font-size:12px}.welcome{padding:50px 0 25px}.welcome h2{font-size:2.65rem}.welcome>p{font-size:1.35rem}.book-facts{gap:25px;justify-content:space-between}.book-facts span{font-size:9px}.book-facts strong{font-size:2.5rem}.feature-links{gap:20px;flex-direction:column}.section-heading h2{font-size:2.4rem}.section-heading>.hugeicon{width:28px;height:28px}.chapter-card{gap:18px}.chapter-card h3{font-size:1.05rem}.card-number{font-size:1.75rem;min-width:30px}.chapter-card p{font-size:10px}.chapter-card .hugeicon{width:18px}.spacetime-lab{border-radius:16px;margin:32px 0 38px}.scene-heading{padding:24px 22px 0}.scene-heading h2{font-size:2.05rem}.scene-heading>p{font-size:11px}.scene-stage,.atlas>.spacetime-lab .scene-stage{height:335px}.scene-label{font-size:12px;padding:1px 4px}.scene-toolbar{margin:0 20px;font-size:9px}.scene-toolbar>span{gap:5px}.scene-toolbar>span .hugeicon{display:none}.scene-toolbar button{width:29px;height:29px}.scene-controls{padding:17px 20px 20px}.scene-controls label{font-size:10px}.scene-controls output{font-size:10px}.range-limits{font-size:8px}.scene-equation.equation{font-size:1.06rem}.scene-note{padding:20px;font-size:9px}.lab-directory{grid-template-columns:1fr}.lab-directory h3{font-size:1.9rem;margin-top:23px}.atlas-grid{grid-template-columns:1fr;gap:32px}.atlas-filters{gap:7px}.atlas-filters button{font-size:9px;padding:9px 12px}.atlas-labs{margin:48px 0}.atlas .chapter-header{padding-top:38px}.atlas-vectors .section-heading>span{display:none}.history-grid{gap:14px}.history-grid img{height:240px;padding:8px}.history-grid figcaption{font-size:9px}.search-header h2{font-size:1.7rem}dialog{padding:22px}#figure-dialog{padding:16px}.large-type .equation{font-size:1.35rem}.key-hint{display:none}}
@media(prefers-reduced-motion:reduce){:root{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}
@media print{.sidebar,.topbar,.section-rail,.page-turn,.site-footer,.reading-tools,.scene-toolbar,.scene-controls,.figure-zoom{display:none}.page{margin:0}.reading-layout{display:block;padding:0}.prose{font-size:11pt}.equation{overflow:visible}.diagram{break-inside:avoid}body{background:white;color:black}}

.scene-heading>p{font-size:13px}.scene-note{font-size:11px}.scene-controls label{font-size:12px}.scene-controls output{font-size:12px}.scene-toolbar{font-size:11px}.range-limits{font-size:10px}.scene-label{font-size:17px}.cover-intro{font-size:14px}.cover-prereq,.cover-model>p{font-size:11px}.diagram figcaption{font-size:12px}.atlas-item .diagram figcaption{font-size:11px}@media(max-width:600px){.scene-heading>p{font-size:12px}.scene-note{font-size:11px}.scene-controls label,.scene-controls output{font-size:10px}.scene-toolbar{font-size:10px}.range-limits{font-size:9px}.scene-label{font-size:13px}.diagram figcaption{font-size:11px}}
.scene-fallback>.gr-figure{max-height:85%;width:100%;height:auto}

.cover-math-compact{display:none}@media(max-width:600px){.cover-math-wide{display:none}.cover-math-compact{display:block;font-size:1.3rem}.cover-equation .cover-math-compact .katex-display>.katex{display:block;text-align:center}}
/* Earth: a moving reference frame, with an explicit playback boundary. */
[data-scene=earth] .scene-stage{background:radial-gradient(ellipse at 48% 48%,color-mix(in srgb,var(--geometry) 8%,var(--figure-bg)),var(--figure-bg) 66%)}
.flow-explanation{margin:0 30px 28px;border-top:1px solid var(--line)}.flow-explanation summary{padding:20px 0 0;cursor:pointer;color:var(--geometry);font-size:12px;font-weight:600}.flow-explanation>div{padding-top:4px}.flow-explanation h3{font:450 1.65rem Newsreader,Georgia,serif;margin:26px 0 10px}.flow-explanation p{font:400 1.14rem/1.75 Newsreader,Georgia,serif;color:var(--ink)}.flow-explanation .equation{font-size:1.2rem;padding:22px 10px}.flow-explanation .flow-credit{font:10px/1.9 Manrope,sans-serif;color:var(--muted)}
@media(max-width:600px){.flow-explanation{margin:0 20px 24px}.flow-explanation summary{font-size:11px}.flow-explanation .equation{font-size:1rem}}
.cover-model [data-scene=earth] .scene-stage{border-radius:18px;background:radial-gradient(ellipse at center,color-mix(in srgb,var(--geometry) 8%,transparent),transparent 72%)}

/* The Earth opening is a centered illustration, with no playback furniture. */
.cover-model{align-self:center;display:grid;place-items:center;background:radial-gradient(ellipse at 50% 50%,color-mix(in srgb,var(--curvature) 8%,transparent),transparent 70%)}
.cover-model>.hero-scene{width:100%}
[data-scene=earth] .scene-stage,.cover-model [data-scene=earth] .scene-stage,.atlas>[data-scene=earth] .scene-stage{width:100%;max-width:680px;aspect-ratio:1;height:auto;margin-inline:auto;background:transparent;border-radius:0}
[data-scene=earth] .scene-stage>canvas{-webkit-mask-image:radial-gradient(ellipse closest-side at center,#000 44%,transparent 100%);mask-image:radial-gradient(ellipse closest-side at center,#000 44%,transparent 100%)}
[data-scene=earth] .scene-stage:focus-visible{outline:2px solid var(--geometry);outline-offset:-5px;border-radius:50%}

/* Search expands within the reading toolbar; the page remains in view. */
.book-search{position:relative;width:96px;transition:width .28s ease;flex-shrink:0}
.book-search.open{width:350px}
.search-field{height:36px;display:flex;align-items:center;border:1px solid transparent;border-radius:10px;background:transparent;transition:border-color .18s,background .18s}
.book-search.open .search-field{border-color:var(--line);background:color-mix(in srgb,var(--paper) 88%,transparent);box-shadow:none}
.book-search #search-button{border:0;margin:0;padding:9px 12px;flex-shrink:0;color:var(--muted)}
.book-search.open #search-button{color:var(--geometry);padding-right:9px}
.book-search.open #search-button span{display:none}
#search-input{width:100%;min-width:0;flex:1;border:0;outline:0;background:transparent;color:var(--ink);font-size:14px;padding:9px 0;border-radius:0}
#search-input::placeholder{color:var(--muted)}
#search-input::-webkit-search-cancel-button{display:none}
#search-close{flex-shrink:0;padding:7px;margin:0 4px;color:var(--muted)}
#search-close .hugeicon{width:17px;height:17px}
.book-search [hidden]{display:none!important}
#search-popover{position:absolute;right:0;top:calc(100% + 12px);width:430px;max-width:calc(100vw - 30px);background:var(--paper);border:1px solid var(--line);border-radius:17px;padding:18px 10px 0;box-shadow:0 18px 50px #0002,0 3px 10px #0001;animation:search-arrive .18s ease-out;overflow:hidden}
.search-caption{display:flex;align-items:center;justify-content:space-between;padding:0 10px;color:var(--geometry);font-size:9px;font-weight:800;letter-spacing:1.8px}
.search-caption .hugeicon{width:19px;height:19px;color:var(--curvature)}
#search-status{margin:8px 10px 14px;font-size:11px;color:var(--muted)}
#search-results{max-height:min(330px,calc(100dvh - 220px));overflow-y:auto;overscroll-behavior:contain;scrollbar-width:thin;padding:0 0 6px}
#search-results:empty{display:none}
#search-results a{display:block;position:relative;text-decoration:none;border:0;padding:12px;border-radius:10px;color:var(--ink);transition:background .15s}
#search-results a+a{margin-top:3px}
#search-results a:hover,#search-results a[aria-selected=true]{background:color-mix(in srgb,var(--ink) 4%,var(--paper))}
.search-chapter{display:block;color:var(--geometry);font-size:8px;letter-spacing:1.4px;font-weight:800;margin-bottom:5px}
#search-results strong{display:block;font-family:Newsreader,Georgia,serif;font-size:21px;font-weight:500;line-height:1.2;letter-spacing:-.02em}
#search-results small{display:-webkit-box;-webkit-box-orient:vertical;-webkit-line-clamp:2;overflow:hidden;color:var(--muted);margin-top:6px;line-height:1.6;font-size:11px}
#search-results mark{background:none;color:var(--ink);font-weight:750}
#search-suggestions{display:flex;flex-wrap:wrap;gap:7px;padding:0 10px 20px}
#search-suggestions button{background:var(--wash);border:1px solid var(--line);border-radius:20px;font-size:11px;padding:6px 11px;transition:border-color .15s,color .15s}
#search-suggestions button:hover{color:var(--geometry);border-color:var(--geometry)}
.search-hint{display:flex;justify-content:space-between;gap:12px;padding:11px 10px;border-top:1px solid var(--line);color:var(--muted);font-size:9px}
@keyframes search-arrive{from{opacity:0;transform:translateY(-5px)}to{opacity:1;transform:translateY(0)}}
@media(max-width:1100px){.topbar.search-open .top-title{display:none}.topbar.search-open .reading-tools{margin-left:auto}}
@media(max-width:600px){.book-search{width:42px}.search-field{border-color:transparent}.book-search.open{position:absolute;left:15px;right:15px;top:10px;width:auto}.topbar.search-open #menu-button,.topbar.search-open #type-button,.topbar.search-open #theme-button{visibility:hidden}.book-search.open .search-field{background:var(--paper)}#search-input{font-size:16px}#search-popover{width:100%;top:calc(100% + 9px)}#search-results strong{font-size:20px}.search-hint{font-size:8px}}
@media(max-width:600px){#search-results{max-height:min(260px,calc(55dvh - 125px))}}

/* A quieter reading surface: spacing carries structure, borders mark results. */
:root{--sidebar-space:var(--sidebar-width)}
html[data-sidebar=collapsed]{--sidebar-space:0px}
.page{margin-left:var(--sidebar-space)}
.reading-progress{left:var(--sidebar-space);width:calc((100% - var(--sidebar-space))*var(--progress,0))}
.sidebar{border-right:0}
.topbar{background:color-mix(in srgb,var(--paper) 64%,transparent);backdrop-filter:blur(22px) saturate(145%);-webkit-backdrop-filter:blur(22px) saturate(145%)}
.top-title{margin-right:auto}
#menu-button{display:inline-flex;flex-shrink:0;color:var(--muted)}
#menu-button span{display:none}
.theme-sun{display:none}
html[data-theme=dark] .theme-sun{display:block}
html[data-theme=dark] .theme-moon{display:none}
.chapter-preparation{font-size:12px;color:var(--muted);margin:0 0 32px}
.chapter-preparation>summary{width:fit-content;cursor:pointer;padding:5px 0}
.chapter-preparation[open]>summary{color:var(--geometry)}
.chapter-guide{border:0;padding:20px 0;margin:0;gap:20px 32px;color:var(--ink)}
.chapter-payoff{border:0;padding-top:0;margin:0}
.prose hr{display:none}
.section-rail nav{border:0}
.section-rail nav a{border:0;border-radius:7px;padding-left:12px}
.section-rail nav a:hover,.section-rail nav a.current{border:0;margin-left:0;background:color-mix(in srgb,var(--geometry) 7%,transparent)}
.equation{border:1px solid transparent;box-shadow:none;background:color-mix(in srgb,var(--wash) 75%,var(--paper))}
.equation:has(.fbox){border-color:color-mix(in srgb,var(--geometry) 38%,var(--line));background:color-mix(in srgb,var(--geometry) 4%,var(--paper))}
.equation .katex .fbox{border:0!important}
.figure-surface,.spacetime-lab,.lab,.takeaway,.checkpoint,.color-key{border:0;box-shadow:none}
.checkpoint[open] summary,.page-turn,.scene-toolbar,.flow-explanation,.color-roles,.scene-equation.equation{border:0}
.checkpoint{background:color-mix(in srgb,var(--paper) 70%,transparent)}
.page-turn{padding-top:24px}
.cover-equation{border:0;overflow:visible;padding:32px 0 0;font-size:1.8rem}
.cover-equation>.eyebrow{margin-bottom:24px}
.cover-equation .katex-display{width:auto;min-width:0;margin:0}
.equation-pieces{display:grid;grid-template-columns:repeat(6,minmax(0,1fr));gap:10px;margin:32px auto 10px;max-width:1000px}
.equation-piece{display:flex;flex-direction:column;align-items:center;justify-content:flex-start;gap:12px;text-decoration:none;border-radius:12px;padding:14px 5px;color:var(--ink);transition:background .15s}
.equation-piece:hover{background:var(--wash)}
.piece-symbol{display:flex;align-items:center;justify-content:center;min-height:58px;font-size:1.3rem}
.piece-label{font-size:10px;line-height:1.5;text-align:center;color:var(--muted)}
.book-contents{padding-top:35px}
.contents-group{margin:36px 0 48px}
.chapter-card,.chapter-card:last-child{border:0;border-radius:13px;padding:18px 16px;gap:23px;margin:4px -16px}
.chapter-card:hover{padding-left:16px;background:var(--wash);color:var(--ink)}
.chapter-visual{width:58px;min-width:58px;height:65px;display:flex;flex-direction:column;justify-content:center;align-items:center;gap:4px;border-radius:13px;background:color-mix(in srgb,currentColor 7%,transparent)}
.chapter-visual .hugeicon{width:25px;height:25px}
.chapter-visual .card-number{min-width:0;font:650 9px Manrope,Arial,sans-serif;letter-spacing:1.4px;color:currentColor;opacity:.8}
.chapter-card h3{margin-bottom:6px}
.appendix-links a{display:flex;align-items:center;gap:13px;padding:7px 0;text-decoration:none}
.appendix-links .hugeicon{width:19px;height:19px;color:var(--muted)}
@media(min-width:801px){html[data-sidebar=collapsed] .sidebar{visibility:hidden;transform:translateX(-100%)}html[data-sidebar=collapsed] .section-rail{display:none}html[data-sidebar=collapsed] .reading-layout{display:block;max-width:1100px}html[data-sidebar=collapsed] .reading-layout:not(:has(>.section-rail)){max-width:1320px}}
@media(max-width:1000px){.equation-pieces{grid-template-columns:repeat(3,minmax(0,1fr));max-width:650px}.cover-equation{font-size:1.55rem}}
@media(max-width:800px){:root{--sidebar-space:0px}#menu-button span{display:inline}.top-title{display:none}.reading-tools{margin-left:auto}}
@media(max-width:600px){.cover-equation{padding:24px 0 0}.cover-equation .cover-math-compact{font-size:1.43rem}.equation-pieces{gap:10px 3px;margin:25px 0 0}.piece-symbol{font-size:1.16rem;min-height:52px}.piece-label{font-size:9px}.equation-piece{padding:9px 3px;gap:8px}.book-contents{padding-top:24px}.chapter-card,.chapter-card:last-child{gap:16px;padding:16px 8px;margin:3px -8px}.chapter-card:hover{padding-left:8px}.chapter-visual{width:44px;min-width:44px;height:56px;border-radius:10px}.chapter-visual .hugeicon{width:22px;height:22px}.chapter-card .card-arrow{display:none}.chapter-guide{padding:16px 0}.takeaway{margin:40px 0}.page-turn{padding-bottom:35px}}

/* One continuous glass header; the contents drawer starts beneath it. */
:root{--header-height:56px}
.topbar{position:fixed;inset:0 0 auto;height:var(--header-height);z-index:40}
.page{padding-top:var(--header-height)}
.sidebar{top:var(--header-height);padding-top:18px}
.sidebar>.brand{display:none}
.reading-progress{left:0;width:calc(100% * var(--progress,0))}
#search-popover{width:100%;max-width:none;top:calc(100% + 8px)}
@media(max-width:800px){:root{--header-height:48px}.sidebar.open{box-shadow:18px 24px 60px #0002}}
@media print{.page{padding-top:0}}

/* Navigation follows Terminalvibes' anchored icon rail: one tree, two widths. */
:root{--sidebar-width:292px;--nav-rail-width:64px;--sidebar-space:var(--sidebar-width);--nav-motion:200ms}
html[data-sidebar=collapsed]{--sidebar-space:var(--nav-rail-width)}
.page{transition:margin-left var(--nav-motion) ease-out}
.topbar{padding-left:10px}
#menu-button{width:44px;height:44px;padding:11px}
#menu-button span{display:none}
.sidebar{width:var(--sidebar-space);padding:0;overflow:hidden;visibility:visible;transform:none;background:color-mix(in srgb,var(--paper) 72%,transparent);backdrop-filter:blur(28px) saturate(145%);-webkit-backdrop-filter:blur(28px) saturate(145%);transition:width var(--nav-motion) ease-out;box-shadow:none}
html[data-sidebar=collapsed] .sidebar{visibility:visible;transform:none}
.nav-inner{width:var(--sidebar-width);height:100%;display:flex;flex-direction:column;padding:12px 0 14px}
.nav-home{flex-shrink:0;margin-bottom:15px}
.nav-scroll{flex:1;min-height:0;overflow:auto;overflow-x:hidden;overscroll-behavior:contain;scrollbar-width:thin;scrollbar-color:transparent transparent;scroll-padding:12px 0}
.nav-scroll{mask-image:linear-gradient(to bottom,#000 calc(100% - 14px),transparent)}
.nav-scroll:hover,.nav-scroll:focus-within{scrollbar-color:color-mix(in srgb,var(--muted) 25%,transparent) transparent}
.nav-group{--nav-accent:var(--geometry);margin:0 0 6px}
.nav-group-toggle,.sidebar .nav-destination{display:flex;align-items:center;gap:0;width:calc(100% - 16px);min-height:48px;margin:0 8px;padding:0;border:0;border-radius:12px;background:transparent;color:var(--muted);text-align:left;text-decoration:none;font:inherit;cursor:pointer}
.nav-group-toggle:hover,.sidebar .nav-destination:hover{background:color-mix(in srgb,var(--ink) 4%,transparent);color:var(--ink)}
.nav-glyph{flex:0 0 48px;height:44px;display:grid;place-items:center}
.nav-glyph .hugeicon{width:21px;height:21px}
.nav-copy{display:block;flex:1;min-width:0;font-size:13px;font-weight:650;line-height:1.5;white-space:nowrap;opacity:1;visibility:visible;transition:opacity var(--nav-motion) ease-out,visibility 0s}
.nav-copy small{display:block;font-size:10px;font-weight:450;color:var(--muted);margin-top:1px}
.nav-caret{width:14px;height:14px;flex-shrink:0;margin:0 15px 0 8px;opacity:.6;transition:transform var(--nav-motion) ease-out,opacity var(--nav-motion) ease-out}
.nav-group-toggle[aria-expanded=true] .nav-caret{transform:rotate(180deg)}
.contains-current>.nav-group-toggle{color:var(--nav-accent)}
.contains-current>.nav-group-toggle .nav-glyph{position:relative}
.contains-current>.nav-group-toggle .nav-glyph:before{content:'';position:absolute;inset:5px;border-radius:10px;background:color-mix(in srgb,var(--nav-accent) 9%,transparent)}
.nav-children,.nav-sections{display:grid;grid-template-rows:0fr;opacity:0;visibility:hidden;transition:grid-template-rows var(--nav-motion) ease-out,opacity var(--nav-motion) ease-out,visibility 0s linear var(--nav-motion)}
.nav-children.is-expanded,.nav-sections.is-expanded{grid-template-rows:1fr;opacity:1;visibility:visible;transition:grid-template-rows var(--nav-motion) ease-out,opacity var(--nav-motion) ease-out,visibility 0s}
.nav-children>div,.nav-sections>div{min-height:0;overflow:hidden}
.nav-children>div{padding:0 12px 0 22px}
.nav-chapter:first-child{margin-top:7px}
.nav-chapter:last-child{margin-bottom:7px}
.nav-chapter-row{display:flex;align-items:center;border-radius:10px;margin:2px 0}
.nav-chapter-row>a{display:flex;align-items:baseline;gap:10px;min-width:0;flex:1;padding:10px 10px;color:var(--muted);text-decoration:none;font-size:12.5px;line-height:1.55;font-weight:500}
.nav-number{font-size:10px;font-variant-numeric:tabular-nums;font-weight:500;opacity:.65;flex:0 0 18px}
.nav-chapter-row:hover{background:color-mix(in srgb,var(--ink) 4%,transparent)}
.is-current>.nav-chapter-row{background:color-mix(in srgb,var(--nav-accent) 9%,transparent)}
.is-current>.nav-chapter-row>a{color:var(--nav-accent);font-weight:750}
.nav-section-toggle{flex-shrink:0;display:grid;place-items:center;border:0;background:transparent;border-radius:7px;color:var(--nav-accent);width:30px;height:30px;padding:7px;margin-right:5px}
.nav-section-toggle:hover{background:color-mix(in srgb,var(--nav-accent) 10%,transparent)}
.nav-section-toggle .hugeicon{width:14px;height:14px;transition:transform var(--nav-motion) ease-out}
.nav-section-toggle[aria-expanded=true] .hugeicon{transform:rotate(180deg)}
.sidebar .nav-sections nav>a{display:block;font-size:11px;line-height:1.65;padding:7px 10px 7px 39px;margin:0;color:var(--muted);font-weight:450;border-radius:8px}
.sidebar .nav-sections nav>a.current{color:var(--nav-accent);background:color-mix(in srgb,var(--nav-accent) 6%,transparent)}
.nav-utilities{flex-shrink:0;padding-top:14px}
.sidebar .nav-utilities .nav-destination{min-height:35px;font-size:11px}
.nav-utilities .nav-glyph{height:35px}
.nav-utilities .nav-glyph .hugeicon{width:18px;height:18px}
.nav-utilities .nav-copy{font-weight:500;font-size:11px}
.sidebar .nav-destination[aria-current=page]{color:var(--geometry);background:color-mix(in srgb,var(--geometry) 8%,transparent)}
html[data-sidebar=collapsed] .nav-copy,html[data-sidebar=collapsed] .nav-caret{opacity:0;visibility:hidden;transition:opacity var(--nav-motion) ease-out,visibility 0s linear var(--nav-motion)}
html[data-sidebar=collapsed] .nav-children{grid-template-rows:0fr;opacity:0;visibility:hidden}
html[data-sidebar=collapsed] .nav-group-toggle,html[data-sidebar=collapsed] .sidebar .nav-destination{width:48px}
.nav-preview{position:fixed;z-index:45;left:64px;width:300px;max-height:calc(100dvh - 88px);padding:16px 12px;margin-left:0;border:1px solid color-mix(in srgb,var(--muted) 18%,transparent);border-radius:16px;background:var(--paper);box-shadow:0 12px 48px #0002;overflow-y:auto;overscroll-behavior:contain;font:13px/1.5 Manrope,sans-serif;color:var(--muted)}
.nav-preview strong{display:block;color:var(--ink);font-weight:750;margin:0 10px 5px}
.nav-preview p{margin:0 10px 12px;font-size:11px}
.nav-preview ol{list-style:none;padding:0;margin:0}
.nav-preview li{margin:2px 0}
.nav-preview a{display:flex;align-items:baseline;gap:10px;min-height:44px;padding:11px 10px;border-radius:9px;color:var(--ink);text-decoration:none}
.nav-preview a:hover,.nav-preview a:focus-visible{background:var(--wash);color:var(--geometry)}
.nav-preview a:focus-visible{outline:2px solid var(--geometry);outline-offset:-2px}
.nav-preview a[aria-current=page]{color:var(--geometry);background:color-mix(in srgb,var(--geometry) 9%,transparent);font-weight:700}
.nav-scrim{position:fixed;inset:var(--header-height) 0 0;z-index:29;border:0;background:#0003;backdrop-filter:blur(3px);-webkit-backdrop-filter:blur(3px)}
@media(max-width:800px){
 :root,html[data-sidebar=collapsed]{--sidebar-space:0px;--sidebar-width:min(308px,calc(100vw - 48px))}
 .sidebar,html[data-sidebar=collapsed] .sidebar{width:var(--sidebar-width);transform:translateX(-100%);visibility:hidden;transition:transform var(--nav-motion) ease-out,visibility 0s linear var(--nav-motion)}
 .sidebar.open,html[data-sidebar=collapsed] .sidebar.open{transform:none;visibility:visible;box-shadow:none;transition:transform var(--nav-motion) ease-out,visibility 0s;background:color-mix(in srgb,var(--paper) 94%,transparent)}
 html[data-sidebar=collapsed] .sidebar .nav-copy,html[data-sidebar=collapsed] .sidebar .nav-caret{opacity:1;visibility:visible}
 html[data-sidebar=collapsed] .sidebar .nav-group-toggle,html[data-sidebar=collapsed] .sidebar .nav-destination{width:calc(100% - 16px)}
 html[data-sidebar=collapsed] .sidebar .nav-children.is-expanded{grid-template-rows:1fr;opacity:1;visibility:visible}
 .nav-preview{display:none}
 body:has(.sidebar.open){overflow:hidden}
 .page{transition:none}
}
@media(prefers-reduced-motion:reduce){:root{--nav-motion:0ms}.sidebar,.nav-copy,.nav-children,.nav-sections{transition:none!important}}
@media print{.sidebar,.nav-preview,.nav-scrim{display:none}.page{margin:0;padding-top:0}}

@media(max-width:800px){body:has(.sidebar.open) .sidebar{z-index:70}body:has(.sidebar.open) .nav-scrim{z-index:69}body:has(.sidebar.open) .topbar{z-index:80}}

/* The Black Hole mark belongs to the app; the toggle belongs to its contents. */
.app-brand{display:flex;align-items:center;gap:20px;min-width:0}
.app-logo{display:grid;place-items:center;width:44px;height:44px;flex-shrink:0;padding:8px;border:0;border-radius:12px;color:var(--ink);background:transparent;text-decoration:none}
.app-logo .hugeicon{width:28px;height:28px}
.app-logo:hover{color:var(--curvature);background:color-mix(in srgb,var(--curvature) 6%,transparent)}
.mobile-logo{display:none}
.nav-home{display:flex;align-items:center;gap:2px;min-height:48px;padding:0 10px}
.nav-home #menu-button{flex:0 0 44px;color:var(--muted)}
.nav-home-link{text-decoration:none;color:var(--ink);padding:10px 0;font-size:12px;font-weight:650}
.nav-home-link:hover{color:var(--geometry)}
@media(max-width:800px){.desktop-logo{display:none}.mobile-logo{display:grid}.app-brand{gap:0}}
@media(max-width:600px){.topbar.search-open .app-brand{visibility:hidden}}

/* One illustration, two complementary views. Scene controls share one quiet edge. */
.spacetime-lab:not(.hero-scene){border-radius:20px;background:color-mix(in srgb,var(--figure-bg) 78%,var(--paper));overflow:visible}
.scene-heading{padding:28px 28px 0}
.scene-heading h2{margin:14px 0 12px;font-size:clamp(1.85rem,3vw,2.45rem);line-height:1.12;letter-spacing:-.025em}
.scene-heading>.eyebrow{font-size:9px;letter-spacing:.13em;color:var(--muted)}
.scene-heading>p{max-width:62ch;line-height:1.75}
.scene-viewbar{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:20px 24px 0;min-height:54px}
.scene-view-switch{display:flex;align-items:center;padding:3px;gap:2px;border-radius:11px;background:color-mix(in srgb,var(--ink) 5%,transparent)}
.scene-view-switch button{display:flex;align-items:center;justify-content:center;gap:6px;min-height:32px;padding:5px 10px;border:0;border-radius:8px;background:transparent;color:var(--muted);font:600 11px Manrope,sans-serif;cursor:pointer;transition:background .16s,color .16s,box-shadow .16s}
.scene-view-switch button[aria-pressed=true]{color:var(--ink);background:var(--paper);box-shadow:0 1px 4px #00000009}
.scene-view-switch button:disabled{opacity:.4;cursor:default}
.scene-view-switch .hugeicon{width:15px;height:15px}
.scene-actions,.scene-camera-tools{display:flex;align-items:center;gap:2px}
.scene-actions button{display:flex;align-items:center;justify-content:center;border:0;border-radius:8px;background:transparent;color:var(--muted);width:32px;height:32px;padding:7px;cursor:pointer}
.scene-actions button:hover{background:color-mix(in srgb,var(--ink) 6%,transparent);color:var(--ink)}
.scene-actions button:focus-visible,.scene-view-switch button:focus-visible{outline:2px solid var(--geometry);outline-offset:3px}
.scene-actions .hugeicon{width:17px;height:17px}
.scene-actions>.passage-tools{position:static;inset:auto;transform:none;display:flex;align-items:center;gap:2px;padding:0;margin:0;background:none;border:0;box-shadow:none;opacity:1;visibility:visible}
.scene-actions>.passage-tools button{width:32px;height:32px;border-radius:8px}
.scene-camera-tools{margin-left:6px}
.scene-camera-tools [data-view=left],.scene-camera-tools [data-view=right]{display:none}
.scene-stage{height:440px;overflow:hidden;background:radial-gradient(ellipse at center,color-mix(in srgb,var(--geometry) 5%,transparent),transparent 72%)}
.scene-label{font-size:16px;line-height:1.25;padding:3px 5px;background:color-mix(in srgb,var(--figure-bg) 88%,transparent);border-radius:5px}
.scene-gesture-hint{position:absolute;bottom:12px;inset-inline:0;text-align:center;color:var(--muted);font-size:9px;letter-spacing:.015em;opacity:.7;pointer-events:none;transition:opacity .18s}
.scene-stage:active .scene-gesture-hint{opacity:0}
.scene-controls{max-width:620px;margin:auto;padding:8px 28px 22px}
.scene-parameter{display:flex;align-items:baseline;justify-content:space-between;gap:16px;min-height:24px}
.scene-controls .scene-parameter label{font-size:11px;line-height:1.55;font-weight:550;min-width:0}
.scene-controls .scene-parameter output{flex:none;float:none;font-size:12px;color:var(--transport);font-variant-numeric:tabular-nums}
.scene-controls input[type=range],.lab input[type=range]{--range-color:var(--transport);appearance:none;-webkit-appearance:none;display:block;width:100%;height:28px;background:transparent;margin:0;cursor:pointer;accent-color:var(--range-color);border:0;border-radius:0;padding:0}
.scene-controls input[type=range]::-webkit-slider-runnable-track,.lab input[type=range]::-webkit-slider-runnable-track{height:2px;border-radius:2px;background:linear-gradient(to right,var(--range-color) 0 var(--range-fill,0%),color-mix(in srgb,var(--ink) 17%,transparent) var(--range-fill,0%) 100%)}
.scene-controls input[type=range]::-webkit-slider-thumb,.lab input[type=range]::-webkit-slider-thumb{appearance:none;-webkit-appearance:none;width:12px;height:12px;margin-top:-5px;background:var(--range-color);border:2px solid var(--paper);border-radius:50%;box-shadow:0 0 0 1px color-mix(in srgb,var(--range-color) 25%,transparent);transition:box-shadow .15s}
.scene-controls input[type=range]:hover::-webkit-slider-thumb,.lab input[type=range]:hover::-webkit-slider-thumb{box-shadow:0 0 0 4px color-mix(in srgb,var(--range-color) 10%,transparent)}
.scene-controls input[type=range]::-moz-range-track,.lab input[type=range]::-moz-range-track{height:2px;border-radius:2px;background:color-mix(in srgb,var(--ink) 17%,transparent)}
.scene-controls input[type=range]::-moz-range-progress,.lab input[type=range]::-moz-range-progress{height:2px;background:var(--range-color)}
.scene-controls input[type=range]::-moz-range-thumb,.lab input[type=range]::-moz-range-thumb{width:9px;height:9px;background:var(--range-color);border:2px solid var(--paper);border-radius:50%;box-shadow:0 0 0 1px color-mix(in srgb,var(--range-color) 25%,transparent)}
.scene-controls input[type=range]:focus-visible,.lab input[type=range]:focus-visible{outline:2px solid color-mix(in srgb,var(--transport) 55%,transparent);outline-offset:2px;border-radius:4px}
.scene-controls .range-limits{font-size:9px;line-height:1.5;color:var(--muted);font-weight:400}
.scene-equation.equation{background:color-mix(in srgb,var(--paper) 45%,transparent);padding:23px 28px;margin:0;border:0;border-radius:0;font-size:1.1rem}
.scene-note{padding:20px 28px 26px;font-size:12px;line-height:1.8}
.scene-note>strong{font-weight:650}
.gr-figure.is-compact [data-compact-hide]{display:none}
.gr-figure [data-compact-only]{display:none}
.gr-figure.is-compact [data-compact-only]{display:inline}
.table-wrap{font-size:16px;line-height:1.7;border:0;border-radius:12px;background:color-mix(in srgb,var(--wash) 50%,var(--paper))}
.table-wrap table{min-width:620px}
.table-wrap th,.table-wrap td{padding:18px 22px;border-bottom-color:color-mix(in srgb,var(--line) 58%,transparent)}
.table-wrap th{font-size:13px;font-weight:700;color:var(--muted);background:color-mix(in srgb,var(--wash) 75%,var(--paper))}
.table-wrap td .katex,.prose .table-wrap td .katex{font-size:1.22em;line-height:1.5}
.table-wrap td:first-child{font-weight:550;min-width:145px}
.table-wrap:focus-visible{outline:2px solid var(--transport);outline-offset:4px}
@media(max-width:600px){.table-wrap{font-size:15px;margin:24px 0}.table-wrap th,.table-wrap td{padding:16px 18px}.table-wrap td .katex,.prose .table-wrap td .katex{font-size:1.22em}}
.scene-diagram[hidden]{display:none}
[data-active-view=diagram] .scene-stage{height:auto!important;min-height:0;background:none;overflow:visible}
[data-active-view=diagram] .scene-fallback,[data-active-view=diagram] .scene-stage>canvas,[data-active-view=diagram] .scene-labels,[data-active-view=diagram] .scene-controls,[data-active-view=diagram] .scene-camera-tools,[data-active-view=diagram] .scene-gesture-hint{display:none!important}
.scene-diagram{padding:14px 18px 6px}
.scene-diagram .diagram{margin:0}
.scene-diagram .figure-surface{background:transparent;border-radius:8px}
.scene-diagram .diagram figcaption{padding:0 10px 15px;font-size:11px;line-height:1.8}
.scene-diagram .figure-zoom{top:8px;right:8px;width:30px;height:30px;background:var(--paper)}
[data-ready=fallback] .scene-controls,[data-ready=fallback] .scene-camera-tools,[data-ready=fallback] .scene-gesture-hint{display:none}
@media(max-width:600px){
 .scene-heading{padding:23px 20px 0}.scene-heading h2{font-size:1.9rem}
 .scene-viewbar{padding:17px 16px 0;gap:6px}
 .scene-view-switch button{padding:5px 8px;font-size:10px;gap:5px}
 .scene-actions button,.scene-actions>.passage-tools button{width:30px;height:32px;padding:6px}
 .scene-camera-tools{margin-left:1px}
 .scene-stage,.atlas>.spacetime-lab .scene-stage{height:340px}
 .scene-label{font-size:13px}
 .scene-controls{padding:5px 20px 21px}
 .scene-controls .scene-parameter label{font-size:10px;max-width:65%}
 .scene-controls .scene-parameter output{font-size:11px}
 .scene-controls .range-limits{font-size:8px}
 .scene-equation.equation{padding:23px 18px;font-size:1.05rem}
 .scene-note{padding:18px 20px 23px}
 .scene-diagram{padding:14px 4px 0}
 .scene-diagram .diagram figcaption{padding:0 16px 16px;font-size:10px}
}
@media(prefers-reduced-motion:reduce){.scene-view-switch button,.scene-gesture-hint,.scene-controls input[type=range]::-webkit-slider-thumb{transition:none}}
@media print{.scene-viewbar,.scene-gesture-hint{display:none}.scene-diagram[hidden]{display:block}.scene-stage{height:auto}.scene-stage>canvas,.scene-labels{display:none}}

/* Compact reading chrome: only the active search becomes a field. */
.topbar{padding-right:24px;gap:14px;border-bottom-color:color-mix(in srgb,var(--line) 55%,transparent)}
.app-brand{gap:14px}.app-logo .hugeicon{width:25px;height:25px}.top-title{letter-spacing:1.65px;font-size:8px}
.reading-tools{gap:3px}.reading-tools>.text-button{width:38px;height:38px;padding:9px}
.reading-tools>.github-link{color:var(--ink);text-decoration:none;flex-shrink:0}
.book-search #search-button{padding:7px 10px;background:none}.book-search #search-button:hover{color:var(--ink);background:none}
.book-search.open #search-button{color:var(--muted)}
#search-suggestions button{border:0;background:color-mix(in srgb,var(--ink) 4%,transparent)}
.search-hint{border-top:0;font-size:9px;padding-top:6px;padding-bottom:12px}
@media(max-width:600px){.topbar{padding-right:14px}.book-search.open{top:6px;left:10px;right:10px}.book-search{width:38px}.book-search #search-button{padding:7px}.reading-tools>.text-button{width:36px;height:36px}.app-logo{height:40px}}
@media(max-width:600px){.topbar.search-open .github-link{visibility:hidden}}
.lab input[type=range]{--range-color:var(--observer);margin:8px 0 18px}
[data-active-view=diagram]>.scene-equation,[data-active-view=diagram]>.scene-note,[data-active-view=diagram]>.scene-explanation{display:none}
@media(max-width:600px){[data-scene=embedding] .scene-stage{height:270px}[data-scene=slices] .scene-stage{height:300px}}

/* Definitions stay out of the reading flow until a symbol is inspected. */
.katex .fbox{pointer-events:none}
#main .katex-html [class*="symbol-"]{cursor:pointer;border-radius:3px;transition:background .15s}
#main .katex-html [class*="symbol-"]:hover,#main .katex-html .symbol-selected{background:color-mix(in srgb,currentColor 13%,transparent)}
.symbol-card{position:fixed;z-index:145;width:min(332px,calc(100vw - 24px));max-height:calc(100dvh - var(--header-height) - 24px);overflow:auto;padding:17px 19px 19px;border:1px solid var(--line);border-radius:17px;background:color-mix(in srgb,var(--paper) 95%,transparent);color:var(--ink);box-shadow:0 14px 46px #0002;backdrop-filter:blur(20px);font-family:Manrope,Arial,sans-serif}
.symbol-card[hidden]{display:none}
.symbol-card-heading{display:flex;align-items:center;gap:10px}
.symbol-card select{min-width:0;flex:1;max-width:100%;border:0;background:transparent;color:var(--ink);font:750 12px Manrope,Arial,sans-serif;cursor:pointer;padding:5px 0}
.symbol-card select:disabled{appearance:none;opacity:1;cursor:default;-webkit-text-fill-color:var(--ink)}
.symbol-card select option{background:var(--paper);color:var(--ink)}
.symbol-close{display:grid;place-items:center;width:30px;height:30px;flex-shrink:0;border:0;border-radius:8px;background:none;color:var(--muted)}
.symbol-close:hover{background:var(--wash);color:var(--ink)}
.symbol-close .hugeicon{width:16px;height:16px}
.symbol-example{font-size:1.55rem;margin:13px 0 17px;min-height:42px;display:flex;align-items:center}
.symbol-type{font-size:9px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);font-weight:650}
.symbol-card p{font-size:12px;line-height:1.85;margin:8px 0 17px}
.symbol-lesson{font-size:11px;font-weight:700;text-decoration:none;color:var(--ink)}
.symbol-lesson:hover{text-decoration:underline;text-underline-offset:4px}
.symbol-card :focus-visible{outline:2px solid var(--ink);outline-offset:3px}
@media(prefers-reduced-motion:reduce){#main .katex-html [class*="symbol-"]{transition:none}}
@media(max-width:380px){.scene-viewbar{padding-inline:12px}.scene-view-switch button{padding-inline:6px}}

/* A chapter opens with reading, with navigation kept in one compact row. */
body[data-page^="chapter-"] .chapter-header{padding:32px 0 20px}
body[data-page^="chapter-"] .breadcrumb{margin-bottom:22px}
body[data-page^="chapter-"] .chapter-header h1{font-size:clamp(2.5rem,4vw,3.6rem);margin:14px 0 18px;max-width:24ch}
body[data-page^="chapter-"] .chapter-deck{font-size:1.35rem;line-height:1.5;margin:0;max-width:58ch}
body[data-page^="chapter-"] .chapter-meta{padding-top:16px}
.chapter-tools{display:flex;flex-wrap:wrap;gap:8px 24px;align-items:baseline;border-block:1px solid var(--line);padding:10px 0;margin:0 0 30px}
.chapter-tools .course-compass{width:100%;margin:0;padding:0}
.chapter-tools .chapter-bridges,.chapter-tools .chapter-preparation{margin:0;font:500 12px/1.6 Manrope,sans-serif}
.chapter-tools details>summary{padding:5px 0}
.chapter-tools details[open]{flex-basis:100%}
.chapter-tools .return-to-lesson{width:100%;margin:0}
.chapter-tools .chapter-guide{margin:12px 0 6px}
.prose>p:first-child{margin-top:0}
.prose>h3:first-child{margin-top:0;padding-top:0}
.prose>h3{margin:2.25em 0 .85em;padding-top:0}
.prose .spacetime-lab{font-family:Manrope,Arial,sans-serif;font-size:1rem;line-height:1.65}
.prose .scene-heading h2{margin:12px 0 18px}
.prose .scene-heading>p{font:400 13px/1.8 Manrope,Arial,sans-serif}
.prose .scene-note{font:400 11px/1.85 Manrope,Arial,sans-serif;margin:0}
.cover-equation{font-size:1.45rem;padding:18px 0}
.cover-equation>summary{font:500 12px/1.6 Manrope,sans-serif;color:var(--muted);cursor:pointer;width:fit-content}
.cover-equation[open]>summary{margin-bottom:28px}
@media(max-width:600px){
 body[data-page^="chapter-"] .chapter-header{padding-top:24px}
 body[data-page^="chapter-"] .breadcrumb{margin-bottom:18px}
 body[data-page^="chapter-"] .chapter-header h1{font-size:2.5rem}
 body[data-page^="chapter-"] .chapter-deck{font-size:1.2rem}
 .chapter-tools{gap:6px 18px;margin-bottom:24px}
 .chapter-tools .course-compass{font-size:11px}
 .prose .equation{padding:16px 12px;margin:24px 0}
}

.history-note{margin:24px 0}
.history-note>summary{font:600 13px/1.7 Manrope,sans-serif;color:var(--geometry);cursor:pointer}

/* Keep disclosure spacing inside its background, independent of paragraph
   margin collapse and the additional semantic reading spans. */
.takeaway{padding:30px}
.takeaway>h2{margin:0 0 14px}
.takeaway>p{margin:0}
.takeaway>.checkpoint{margin:24px 0 0}
.checkpoint{padding:0 22px;display:flow-root}
.checkpoint>summary{padding:18px 0}
.checkpoint[open]{padding-bottom:22px}
.checkpoint>:not(summary){margin:0 0 18px}
.checkpoint>:last-child{margin-bottom:0}
.spacetime-lab:not(.hero-scene){display:flow-root}
.spacetime-lab:has(>.flow-explanation)>.scene-note{padding-bottom:12px}
.flow-explanation{margin:0;padding:0 28px 14px}
.flow-explanation>summary{padding:14px 0}
.flow-explanation[open]{padding-bottom:28px}
.flow-explanation>div{display:flow-root;padding:4px 0 0}
.flow-explanation>div>:first-child{margin-top:0}
.flow-explanation>div>:last-child{margin-bottom:0}
@media(max-width:600px){
 .takeaway{padding:22px}
 .checkpoint{padding-inline:18px}
 .checkpoint[open]{padding-bottom:18px}
 .flow-explanation{padding-inline:20px}
 .flow-explanation[open]{padding-bottom:24px}
}