@font-face{font-family:Readex;src:url(readex.woff2) format('woff2');font-weight:300 600;font-display:swap}
@font-face{font-family:Amiri;src:url(amiri.woff2) format('woff2');font-weight:400;font-display:swap}
@font-face{font-family:'Source Serif';src:url(sourceserif4.c00fc5debabb.woff2) format('woff2');font-weight:400 650;font-style:normal;font-display:swap}
@font-face{font-family:'Source Serif';src:url(sourceserif4-italic.8ba79751044b.woff2) format('woff2');font-weight:400 650;font-style:italic;font-display:swap}

:root{color-scheme:light;--paper:#fff;--ink:#1d2731;--ink-2:#33404b;--muted:#5b6772;--faint:#8b96a0;--line:#e3e7ea;--line-2:#cdd5dc;--accent:#2b5884;--accent-ink:#1d4064;--focus:#8fb2d3;--fault:#c8473a;--good:#d3dae0;--flag:#e09a1b;--felt:#a96b12;--test:#2b5884;--up:#2e7a58;--down:#c8473a;--sans:Readex,'Segoe UI',system-ui,-apple-system,Arial,sans-serif;--serif:'Source Serif','Iowan Old Style','Palatino Linotype',Georgia,'Noto Serif',serif;--measure:800px}
html[lang=ar]{--serif:Amiri,'Noto Naskh Arabic','Times New Roman',serif}
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;text-size-adjust:100%;scroll-padding-top:76px}
body{margin:0;background:#fff;color:var(--ink);font:400 16px/1.6 var(--sans);text-rendering:optimizeLegibility;-webkit-font-smoothing:antialiased;overflow-x:clip}
h1,h2,h3,h4,p,ol,ul,dl,dd,figure{margin:0}
a{color:var(--accent);text-underline-offset:3px;text-decoration-thickness:1px}
a:hover{color:var(--accent-ink)}
button{font:inherit;color:inherit;background:none;border:0;padding:0;cursor:pointer}
button:disabled{cursor:default}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px;border-radius:4px}
strong,b{font-weight:600}
var{font-family:var(--serif);font-style:italic}
html[lang=ar] var{font-style:normal}
bdi{unicode-bidi:isolate}
html:not(.js) .js-only{display:none!important}
.js .parts-static,.js .nojs-answer{display:none}

.skip-link{position:fixed;inset-block-start:-90px;inset-inline-start:16px;z-index:70;padding:10px 16px;background:#fff;border:2px solid var(--accent);border-radius:6px}
.skip-link:focus{inset-block-start:10px}
.read-progress{position:fixed;inset-inline:0;top:0;height:3px;z-index:60;pointer-events:none}
.read-progress span{display:block;height:100%;background:var(--accent);transform:scaleX(0);transform-origin:0 50%}
html[dir=rtl] .read-progress span{transform-origin:100% 50%}
.site-header{height:58px;position:sticky;top:0;z-index:30;background:#fff;border-bottom:1px solid var(--line);padding-inline:max(20px,calc((100vw - var(--measure))/2));display:flex;justify-content:space-between;align-items:center;gap:20px}
.brand{display:flex;align-items:center;gap:10px;font-size:14px;color:var(--ink);text-decoration:none}
.brand-monogram{font:italic 600 26px/1 'Source Serif',Georgia,serif;direction:ltr;color:var(--accent)}
.header-nav{display:flex;align-items:center;gap:18px;font-size:14px}
.header-nav a{text-decoration:none}
.header-divider{height:16px;width:1px;background:var(--line)}
.language-switch span{color:var(--muted)}

.research-essay,.series-dashboard{width:100%;max-width:calc(var(--measure) + 40px);margin:0 auto;padding:34px 20px 0}
.heading-top{display:flex;justify-content:space-between;align-items:center;gap:15px;margin-bottom:26px}
.article-back{font-size:14px;text-decoration:none;color:var(--muted)}
.eyebrow{font:500 12px/1.6 var(--sans);letter-spacing:.08em;color:var(--muted)}
.article-heading h1{font:430 clamp(40px,6.4vw,60px)/1.04 var(--serif);letter-spacing:-.022em;color:var(--ink);text-wrap:balance}
.article-heading h1 em{font-style:italic;font-weight:430;color:var(--accent)}
.hero-deck{font:italic 400 clamp(19px,2.4vw,23px)/1.5 var(--serif);color:var(--ink-2);margin-top:22px;max-width:44em;text-wrap:pretty}
.byline{display:flex;align-items:center;gap:12px;flex-wrap:wrap;font-size:14px;color:var(--muted);margin-top:24px}
.byline a{color:var(--ink);text-decoration:none;font-weight:500}
.byline .sep{width:4px;height:4px;border-radius:50%;background:var(--line-2)}
.article-status{display:flex;gap:8px 20px;align-items:center;flex-wrap:wrap;font-size:14px;color:var(--muted);margin-top:8px}
.article-status a{text-decoration:none}
.tags{display:flex;gap:6px;list-style:none;flex-wrap:wrap;padding:0;margin:16px 0 0;font-size:12.5px;color:var(--muted)}
.tags li{border:1px solid var(--line);border-radius:999px;padding:3px 11px}

.essay-body{margin-top:34px;border-top:1px solid var(--line);padding-top:30px}
.short-version h2{font:600 13px/1.4 var(--sans);letter-spacing:.08em;text-transform:uppercase;color:var(--accent)}
.short-list{list-style:none;counter-reset:s;padding:0;margin:14px 0 0;display:grid;gap:2px}
.short-list li{counter-increment:s;display:grid;grid-template-columns:30px minmax(0,1fr);align-items:baseline}
.short-list li::before{content:counter(s);font:600 14px var(--sans);color:var(--accent)}
.short-list a{display:block;padding:7px 0;font:400 19px/1.5 var(--serif);color:var(--ink);text-decoration:none;border-bottom:1px solid transparent}
.short-list a:hover{color:var(--accent-ink);text-decoration:underline;text-decoration-color:var(--line-2)}
.qualification{margin-top:16px;padding:4px 0 4px 14px;padding-inline:14px 0;border-inline-start:3px solid var(--flag);font:14.5px/1.65 var(--sans);color:var(--ink-2)}
.chapter-roadmap{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));border-block:1px solid var(--line);margin-top:28px}
.chapter-roadmap a{display:grid;grid-template-columns:auto minmax(0,1fr);gap:10px;padding:16px 14px;text-decoration:none;color:var(--ink);border-inline-start:1px solid var(--line);transition:background .2s}
.chapter-roadmap a:first-child{border-inline-start:0;padding-inline-start:0}
.chapter-roadmap a.active strong{color:var(--accent)}
.chapter-number{font:600 13px var(--sans);color:var(--accent);padding-top:2px}
.chapter-roadmap strong{display:block;font:600 15px/1.35 var(--sans)}
.chapter-roadmap small{display:block;font:13px/1.45 var(--sans);color:var(--muted);margin-top:3px}
.reading-toolbar{display:flex;flex-wrap:wrap;align-items:center;gap:10px 16px;margin-top:22px}
.toolbar-label{font:600 13px var(--sans);color:var(--muted)}
.toolbar-hint{flex-basis:100%;font:13px/1.5 var(--sans);color:var(--muted)}
.seg{display:inline-flex;flex-wrap:wrap;gap:3px;padding:3px;border:1px solid var(--line-2);border-radius:999px;background:#fff}
.seg button{padding:8px 15px;border-radius:999px;font:500 14px/1.2 var(--sans);color:var(--muted);transition:background .2s,color .2s}
.seg button span{margin-inline-start:8px;font-weight:400;opacity:.8}
.seg button:hover{color:var(--ink)}
.seg button[aria-pressed=true]{background:var(--accent);color:#fff}

.essay-section{padding-top:80px;scroll-margin-top:70px}
.essay-section+.essay-section{padding-top:0}
.essay-section+.essay-section::before{content:'\00B7\2003\00B7\2003\00B7';display:block;text-align:center;font:600 22px/1 var(--serif);color:var(--faint);margin:76px 0 60px}
#the-gap .prose>p:first-child{font-size:26px;line-height:1.5;color:var(--ink);letter-spacing:-.005em}
html[lang=ar] #the-gap .prose>p:first-child{font-size:28px;line-height:1.8}
.section-tag{display:flex;align-items:center;gap:10px;font:600 13px/1 var(--sans);letter-spacing:.07em;text-transform:uppercase;color:var(--muted)}
.section-num{display:inline-grid;place-items:center;min-width:30px;height:24px;padding:0 6px;border-radius:999px;border:1px solid var(--line-2);color:var(--accent);letter-spacing:0}
.essay-section h2{font:500 clamp(30px,4.2vw,42px)/1.14 var(--serif);letter-spacing:-.02em;margin-top:18px;text-wrap:balance}
.lede{font:italic 400 22.5px/1.55 var(--serif);color:var(--muted);margin-top:16px;text-wrap:pretty}
.expand-section{display:none;margin-top:14px;font:500 14px var(--sans);color:var(--accent);text-decoration:underline;text-underline-offset:3px}
.prose{margin-top:36px}
.prose>p,.prose li p{font:400 21.5px/1.78 var(--serif);color:var(--ink);margin-bottom:1.3em;text-wrap:pretty;font-kerning:normal;hanging-punctuation:first}
.prose em{font-style:italic}
.citation{font:500 11px/1 var(--sans);opacity:.75;padding:3px 1px;text-decoration:none;white-space:nowrap;vertical-align:super;line-height:0}
sup{line-height:0}
.takeaway{position:relative;margin:30px 0 0;padding:6px 0 6px 26px;padding-inline:26px 0;border-inline-start:3px solid var(--accent);font:500 25px/1.42 var(--serif);letter-spacing:-.01em;color:var(--accent-ink);text-wrap:balance}
.takeaway.final-thought{font-size:29px;padding-block:10px}
.principles{list-style:none;counter-reset:p;padding:0;margin:8px 0 22px;display:grid;gap:4px}
.principles li{counter-increment:p;display:grid;grid-template-columns:40px minmax(0,1fr);column-gap:6px;padding:14px 0;border-top:1px solid var(--line)}
.principles li::before{content:counter(p);grid-row:span 2;display:grid;place-items:center;width:30px;height:30px;border-radius:50%;background:var(--accent);color:#fff;font:600 14px var(--sans)}
.principles h3{font:600 17px/1.4 var(--sans);margin:4px 0 6px}
.principles li p{font-size:19.5px;margin:0}

.fig{margin:44px 0 52px;border:1px solid var(--line);border-radius:18px;padding:26px 28px 20px;background:#fff;box-shadow:0 18px 40px -34px rgba(20,40,60,.45)}
.fig-label{font:600 12px/1.4 var(--sans);letter-spacing:.09em;text-transform:uppercase;color:var(--accent)}
.fig-title{font:500 25px/1.25 var(--serif);margin-top:6px;letter-spacing:-.01em;text-wrap:balance}
.fig figcaption{margin-top:20px;padding-top:12px;border-top:1px solid var(--line);font:13.5px/1.6 var(--sans);color:var(--muted)}
.small-note{font:13px/1.55 var(--sans);color:var(--muted)}
.button{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:44px;padding:10px 18px;border-radius:999px;border:1px solid var(--line-2);background:#fff;font:500 15px/1.2 var(--sans);color:var(--ink);transition:background .2s,border-color .2s,color .2s,transform .1s}
.button:hover{border-color:var(--accent)}
.button:active{transform:translateY(1px)}
.button.primary{background:var(--accent);border-color:var(--accent);color:#fff}
.button.primary:hover{background:var(--accent-ink);border-color:var(--accent-ink)}
.button:disabled{opacity:.4}
.button[aria-pressed=true]{border-color:var(--accent);box-shadow:inset 0 0 0 1px var(--accent);color:var(--accent-ink)}
.button.correct{border-color:var(--up);box-shadow:inset 0 0 0 1px var(--up);color:var(--up)}
.text-button{font:500 14px/1.4 var(--sans);color:var(--accent);text-decoration:underline;text-underline-offset:3px;padding:8px 0}
.choice{display:flex;flex-wrap:wrap;gap:8px}
.fig-nav{display:flex;align-items:center;justify-content:space-between;gap:10px;flex-wrap:wrap;margin-top:18px}
.range-label{display:flex;justify-content:space-between;align-items:baseline;gap:12px;font:500 15px var(--sans)}
.range-label output{font:600 24px/1 var(--sans);color:var(--accent);font-variant-numeric:tabular-nums}
input[type=range]{-webkit-appearance:none;appearance:none;width:100%;height:32px;background:transparent;margin:6px 0 0;cursor:pointer}
input[type=range]::-webkit-slider-runnable-track{height:6px;border-radius:3px;background:var(--line)}
input[type=range]::-moz-range-track{height:6px;border-radius:3px;background:var(--line)}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:24px;height:24px;margin-top:-9px;border-radius:50%;background:#fff;border:2px solid var(--accent);box-shadow:0 2px 6px rgba(20,40,60,.25)}
input[type=range]::-moz-range-thumb{width:22px;height:22px;border-radius:50%;background:#fff;border:2px solid var(--accent);box-shadow:0 2px 6px rgba(20,40,60,.25)}
input[type=range]:focus-visible{outline:none}
input[type=range]:focus-visible::-webkit-slider-thumb{outline:3px solid var(--focus);outline-offset:2px}
.range-ends{display:flex;justify-content:space-between;font:12.5px var(--sans);color:var(--muted)}
.spark{display:inline-block;width:16px;height:16px;border-radius:50%;background:var(--accent);box-shadow:0 0 0 4px #dbe6f0}

.formula{display:flex;align-items:center;flex-wrap:wrap;gap:6px 9px;margin:12px 0;font:400 19px/1.4 var(--serif);color:var(--ink)}
html[lang=ar] .formula{font-size:21px}
.frac{display:inline-flex;flex-direction:column;align-items:center;vertical-align:middle}
.frac .num{padding:0 5px 4px;border-bottom:1.5px solid currentColor}
.frac .den{padding:4px 5px 0}
.formula .res{color:var(--accent);font-weight:600}
.expr{white-space:nowrap}

.pz-body{display:flex;gap:18px;align-items:flex-start;margin-top:16px}
.pz-lamp{flex:0 0 58px;width:58px;height:58px;margin-top:4px}
.lamp-glow{fill:#f3b23c;opacity:.22;transform-origin:32px 27px;animation:glow 2.6s ease-in-out infinite}
.lamp-body{fill:var(--flag)}
.lamp-base{fill:var(--ink-2)}
.lamp-ray{stroke:var(--flag);stroke-width:3;stroke-linecap:round;fill:none}
@keyframes glow{50%{opacity:.42;transform:scale(1.08)}}
.pz-text>p:first-child{font:400 18px/1.55 var(--serif)}
.pz-facts{list-style:none;padding:0;margin:10px 0 12px;display:grid;gap:4px}
.pz-facts li{position:relative;padding-inline-start:20px;font:16px/1.55 var(--sans)}
.pz-facts li::before{content:'';position:absolute;inset-inline-start:2px;top:.62em;width:8px;height:8px;border-radius:2px;background:var(--accent)}
.pz-q{font:600 19px/1.45 var(--serif);color:var(--ink)}
.pz-guess{display:grid;gap:4px;margin-top:20px;padding-top:16px;border-top:1px dashed var(--line-2)}
.pz-guess .button{justify-self:start;margin-top:10px}
.pz-answer{margin-top:20px}
.js .fig-puzzle[data-state=guess] .pz-answer{display:none}
.js .fig-puzzle[data-state=answer] [data-reveal]{display:none}
.js .fig-puzzle[data-state=answer] .pz-answer{animation:rise .45s ease-out both}
.answer-card{border:1px solid var(--line-2);border-radius:14px;padding:16px 18px;background:#fff}
.answer-card>p{font:16px/1.65 var(--sans);color:var(--ink)}
.answer-head{display:flex;align-items:center;flex-wrap:wrap;gap:8px 10px;margin-bottom:8px}
.answer-head span:last-child{font-size:13px;color:var(--muted)}
.pz-compare{margin-top:16px}
.pz-legend,.z-legend{display:flex;align-items:center;gap:6px 14px;flex-wrap:wrap;font:13px var(--sans);color:var(--muted)}
.key{display:inline-block;width:12px;height:12px;border-radius:50%;margin-inline-end:-6px}
.key.guess{background:var(--flag)}
.key.truth{background:var(--accent)}
.pz-line{position:relative;height:30px;margin:8px 10px 0}
.pz-axis{position:absolute;inset-inline:0;top:13px;height:4px;border-radius:2px;background:var(--line-2)}
.pz-tick{position:absolute;top:8px;width:2px;height:14px;margin-inline-start:-1px;background:var(--line-2)}
.pz-tick.t0{inset-inline-start:0}.pz-tick.t50{inset-inline-start:50%}.pz-tick.t100{inset-inline-start:100%}
.pz-gap{position:absolute;top:14px;height:0;border-top:2px dashed var(--fault);inset-inline-start:8.3%;inline-size:41.7%;transition:inset-inline-start .5s,inline-size .5s}
.pz-dot{position:absolute;top:15px;width:16px;height:16px;margin:-8px;margin-inline-start:-8px;border-radius:50%;border:2px solid #fff;box-shadow:0 1px 4px rgba(20,40,60,.35)}
.pz-dot.truth{background:var(--accent);inset-inline-start:8.3%}
.pz-dot.guess{background:var(--flag);inset-inline-start:50%;transition:inset-inline-start .5s}
.pz-result{margin-top:8px;font:600 16px/1.5 var(--sans)}

.stepper{list-style:none;padding:0;margin:18px 0 0;display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:6px}
.stepper button{display:flex;flex-direction:column;align-items:flex-start;gap:7px;width:100%;height:100%;padding:10px;border:1px solid var(--line);border-radius:12px;text-align:start;font:500 13px/1.3 var(--sans);color:var(--muted);transition:border-color .2s,color .2s}
.stepper button:hover{border-color:var(--line-2);color:var(--ink)}
.stepper button[aria-pressed=true]{border-color:var(--accent);box-shadow:inset 0 0 0 1px var(--accent);color:var(--ink)}
.sn{display:inline-grid;place-items:center;min-width:24px;height:24px;border-radius:999px;border:1px solid var(--line-2);font:600 12px/1 var(--sans);color:var(--muted)}
.stepper button[aria-pressed=true] .sn,.rs-steps button[aria-pressed=true] .sn{background:var(--accent);border-color:var(--accent);color:#fff}
.stepper button.done .sn{border-color:var(--accent);color:var(--accent)}
.parts-stage{margin-top:16px}
.parts-svg{display:block;width:100%;height:auto}
html[dir=rtl] .parts-svg{transform:scaleX(-1)}
.parts-svg .c{fill:var(--good);stroke:transparent;stroke-width:1.7;vector-effect:non-scaling-stroke;transition:fill .45s ease,stroke .35s ease,opacity .5s ease,transform .8s cubic-bezier(.2,.75,.2,1)}
.parts-svg .c.f{fill:var(--fault)}
.parts-svg .c.w{stroke:var(--flag)}
.parts-svg[data-step="0"] .c.f{fill:var(--good)}
.parts-svg[data-step="0"] .c.w,.parts-svg[data-step="1"] .c.w,.parts-svg[data-step="2"] .c.g.w{stroke:transparent}
.parts-svg[data-step="4"] .c:not(.w){opacity:0}
.parts-legend{display:flex;flex-wrap:wrap;gap:6px 18px;margin-top:12px;font:13px var(--sans);color:var(--muted)}
.lg{display:inline-block;width:12px;height:12px;border-radius:3px;vertical-align:-1px;margin-inline-end:7px}
.lg-f{background:var(--fault)}
.lg-g{background:var(--good)}
.lg-w{background:#fff;box-shadow:inset 0 0 0 2px var(--flag)}
.parts-caption{margin-top:16px;min-height:96px}
.step-count{font:600 12px var(--sans);letter-spacing:.06em;text-transform:uppercase;color:var(--muted)}
.step-title{font:500 20px/1.35 var(--serif);margin-top:4px}
.step-text{font:16.5px/1.6 var(--sans);margin-top:4px;color:var(--ink)}
.parts-static{margin-top:14px;padding-inline-start:20px;font:15.5px/1.6 var(--sans)}
.parts-static li{margin-bottom:4px}
.parts-counts{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin-top:16px;padding-top:14px;border-top:1px solid var(--line)}
.parts-counts dt{font:13px/1.4 var(--sans);color:var(--muted)}
.parts-counts dd{font:600 28px/1.2 var(--sans);font-variant-numeric:tabular-nums;margin-top:2px;transition:color .3s}
.parts-counts dd[data-k=share]{color:var(--accent)}
.parts-counts dd.pending{color:var(--line-2)}
.parts-rate{margin-top:16px;padding-top:14px;border-top:1px dashed var(--line-2)}
.js .fig-parts:not([data-step="4"]) .parts-rate{display:none}

.desk-board{margin-top:16px;border:1px dashed var(--line-2);border-radius:16px;padding:18px;min-height:212px}
.desk-group-label{font:600 14px var(--sans);color:var(--muted);margin-bottom:10px}
.js .desk-group{display:none}
.js .desk-group.on{display:block}
.js .desk-group-label{display:none}
html:not(.js) .desk-group+.desk-group{margin-top:20px;padding-top:16px;border-top:1px solid var(--line)}
.desk-cards{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px}
.desk-cards.n2{grid-template-columns:repeat(2,minmax(0,1fr));max-width:460px}
.desk-cards li{border:1px solid var(--line-2);border-radius:10px;padding:12px 13px;font:14.5px/1.4 var(--sans);background:#fff;box-shadow:0 6px 14px -12px rgba(20,40,60,.55);animation:deal .38s cubic-bezier(.2,.75,.2,1) both}
.desk-cards.n2 li{font-size:17px;padding:16px}
.desk-cards li:nth-child(2){animation-delay:.05s}.desk-cards li:nth-child(3){animation-delay:.1s}.desk-cards li:nth-child(4){animation-delay:.15s}.desk-cards li:nth-child(5){animation-delay:.2s}.desk-cards li:nth-child(6){animation-delay:.25s}
.desk-cards.n6 li:nth-child(odd){transform:rotate(-.8deg)}
.desk-cards.n6 li:nth-child(even){transform:rotate(.7deg)}
@keyframes deal{from{opacity:0;translate:0 10px}}
.desk-count{display:flex;align-items:center;gap:12px;margin-top:16px;font:600 15px var(--sans)}
.load{display:inline-flex;gap:4px}
.load i{width:11px;height:11px;border-radius:50%;background:var(--accent)}

.z-stage{margin-top:16px}
.js .fig-zipper .z-stage{display:none}
.js .fig-zipper[data-stage="1"] .z1,.js .fig-zipper[data-stage="2"] .z2,.js .fig-zipper[data-stage="3"] .z3,.js .fig-zipper[data-stage="4"] .z4{display:block;animation:rise .35s ease-out both}
.z-prompt{font:600 17px/1.5 var(--sans)}
.scale{display:flex;gap:6px;flex-wrap:wrap;margin-top:12px}
.scale button{width:42px;height:42px;border-radius:50%;border:1px solid var(--line-2);font:600 16px var(--sans);color:var(--ink);transition:background .15s,border-color .15s,color .15s}
.scale button:hover{border-color:var(--accent)}
.scale button[aria-pressed=true]{background:var(--accent);border-color:var(--accent);color:#fff}
.scale-ends{display:flex;justify-content:space-between;max-width:330px;margin-top:6px;font:12.5px var(--sans);color:var(--muted)}
.z-prompts{margin:10px 0 14px;padding-inline-start:22px}
.z-prompts li{font:400 18px/1.55 var(--serif);margin-bottom:4px}
.z-compare{display:block;width:100%;max-width:420px;height:auto;margin-top:6px}
.z-compare .axis{stroke:var(--line-2);stroke-width:3;stroke-linecap:round}
.z-compare .tick{font:600 12px var(--sans);fill:var(--muted)}
.z-compare .drop{stroke:var(--fault);stroke-width:2;stroke-dasharray:4 4}
.z-compare .before{fill:var(--felt)}
.z-compare .after{fill:var(--accent)}
.key.before{background:var(--felt)}
.key.after{background:var(--accent)}
.z-result{font:600 16px/1.5 var(--sans);margin-top:8px}
.z-how{margin-top:18px;border-top:1px solid var(--line);padding-top:12px}
.z-how>summary,.t-example>summary,.rs-row>summary,.source-detail>summary{list-style:none;cursor:pointer}
.z-how>summary::-webkit-details-marker,.t-example>summary::-webkit-details-marker,.rs-row>summary::-webkit-details-marker,.source-detail>summary::-webkit-details-marker{display:none}
.z-how>summary{display:inline-flex;align-items:center;gap:8px;font:600 15px var(--sans);color:var(--accent)}
.z-how>summary::before,.t-example>summary::before,.rs-row>summary::before{content:'+';display:inline-grid;place-items:center;width:22px;height:22px;border-radius:50%;border:1px solid currentColor;font:600 14px/1 var(--sans)}
.z-how[open]>summary::before,.t-example[open]>summary::before,.rs-row[open]>summary::before{content:'−'}
.z-how-body{display:grid;grid-template-columns:minmax(0,240px) minmax(0,1fr);gap:22px;align-items:center;margin-top:14px}
.z-svg{width:100%;height:auto}
.z-svg .tape{fill:#eef1f4;stroke:#c9d2da}
.z-svg .tooth.l{fill:#a7b3bd}
.z-svg .tooth.r{fill:#6f7f8c}
.z-svg .slider{fill:#fff;stroke:var(--ink);stroke-width:1.6;stroke-linejoin:round}
.z-svg .wedge{fill:var(--ink-2)}
.z-svg .leader{stroke:var(--accent);stroke-width:1.2;stroke-dasharray:3 3}
.z-svg .marker{fill:#fff;stroke:var(--accent);stroke-width:1.8}
.z-svg .marker-n{font:600 12px var(--sans);fill:var(--accent)}
.z-how-list{padding-inline-start:22px;margin:0}
.z-how-list li{font:15.5px/1.6 var(--sans);margin-bottom:8px}
.z-how-list li::marker{color:var(--accent);font-weight:600}

.felt-table{margin-top:14px}
.felt-row{display:grid;grid-template-columns:minmax(0,1.25fr) minmax(0,1fr) minmax(0,1fr);gap:18px;padding:16px 0;border-top:1px solid var(--line);align-items:start}
.felt-headrow{border-top:0;padding:0 0 8px}
.felt-headrow .ch{font:600 12px var(--sans);letter-spacing:.08em;text-transform:uppercase}
.ch.felt{color:var(--felt)}
.ch.test{color:var(--test)}
.felt-study{font:15.5px/1.5 var(--sans);color:var(--ink)}
.felt-cell{display:flex;gap:11px;align-items:flex-start;font:15px/1.45 var(--sans);color:var(--ink-2)}
.arrow{flex:0 0 34px;width:34px;height:34px;border-radius:50%;display:grid;place-items:center;border:2px solid currentColor}
.felt-cell.felt .arrow{color:var(--felt)}
.felt-cell.test .arrow{color:var(--test)}
.arrow svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2.4;stroke-linecap:round;stroke-linejoin:round}

.cr-chart{position:relative;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:26px;margin-top:16px}
.cr-panel{position:relative;padding-top:4px}
.cr-phase{font:600 15px var(--sans);margin-bottom:14px}
.cr-row{margin-bottom:16px}
.cr-arm{font:13.5px/1.4 var(--sans);color:var(--muted);margin-bottom:6px}
.cr-track{position:relative;height:32px;--zero:22.5%}
.cr-zero{position:absolute;top:-4px;bottom:-4px;inset-inline-start:var(--zero);border-inline-start:2px solid var(--ink)}
.cr-bar{position:absolute;top:4px;height:24px;border-radius:5px;inset-inline-start:calc(var(--zero) + var(--from));inline-size:var(--len);transition:transform .9s cubic-bezier(.2,.75,.2,1);transform-origin:0 50%}
.cr-bar.base-p{--from:0%;--len:24%;background:var(--up)}
.cr-bar.tutor-p{--from:0%;--len:63.5%;background:var(--up)}
.cr-bar.base-e{--from:-8.5%;--len:8.5%;background:var(--down);transform-origin:100% 50%}
.cr-bar.tutor-e{--from:-.6%;--len:1.2%;background:var(--muted)}
html[dir=rtl] .cr-bar{transform-origin:100% 50%}
html[dir=rtl] .cr-bar.base-e{transform-origin:0 50%}
.cr-val{position:absolute;top:6px;font:600 15px/1.3 var(--sans);white-space:nowrap;transition:opacity .5s .5s}
.cr-val small{font-weight:400;font-size:12.5px;color:var(--muted)}
.cr-val.base-p{inset-inline-start:calc(var(--zero) + 24% + 8px)}
.cr-val.tutor-p{inset-inline-start:calc(var(--zero) + 63.5% + 8px)}
.cr-val.base-e{inset-inline-end:calc(100% - var(--zero) + 8.5% + 7px)}
.cr-val.tutor-e{inset-inline-start:calc(var(--zero) + 10px)}
.cr-val.base-p,.cr-val.tutor-p{color:var(--up)}
.cr-val.base-e{color:var(--down)}
.cr-veil{display:none;position:absolute;inset:34px 0 0;place-items:center;background:rgba(255,255,255,.86);border-radius:12px}
.js .fig-crutch[data-revealed=false] .cr-veil{display:grid}
.js .fig-crutch[data-revealed=false] [data-phase=exam] .cr-bar{transform:scaleX(0)}
.js .fig-crutch[data-revealed=false] [data-phase=exam] .cr-val{opacity:0;transition:none}
.js .fig-crutch[data-revealed=false] [data-replay]{visibility:hidden}
.cr-zero-key{display:flex;align-items:center;gap:10px;margin-top:4px;font:13.5px var(--sans);color:var(--ink-2)}
.zero-swatch{width:2px;height:18px;background:var(--ink)}
.cr-axis{font:13px var(--sans);color:var(--muted);margin-top:4px}

.rs-steps{list-style:none;padding:0;margin:16px 0 0;display:flex;gap:6px;flex-wrap:wrap}
.rs-steps button{display:inline-flex;align-items:center;gap:8px;padding:6px 13px 6px 7px;padding-inline:7px 13px;border:1px solid var(--line-2);border-radius:999px;font:500 13.5px/1.2 var(--sans);color:var(--muted);transition:border-color .2s,color .2s}
.rs-steps button:hover{color:var(--ink)}
.rs-steps button[aria-pressed=true]{border-color:var(--accent);color:var(--ink)}
.rs-steps button.done .sn{border-color:var(--accent);color:var(--accent)}
.rs-note{margin:14px 0 12px;font:15.5px/1.55 var(--sans);color:var(--ink);min-height:3.1em}
.rs-count{font-weight:600;color:var(--accent);margin-inline-end:4px}
.rs-card{border:1px solid var(--line-2);border-radius:16px;padding:18px 20px;background:#fff;box-shadow:0 14px 30px -24px rgba(20,40,60,.55)}
.rs-card-head{display:flex;align-items:center;gap:10px;font:600 13.5px var(--sans);color:var(--muted);margin-bottom:12px}
.rs-card>*{animation:rise .35s ease-out both}
.rs-purpose{margin-bottom:12px;padding-bottom:12px;border-bottom:1px dashed var(--line-2)}
.rs-purpose>p{font:600 13px var(--sans);color:var(--muted);margin-bottom:8px}
.rs-purpose .button{min-height:38px;padding:7px 14px;font-size:14px}
.lead-v{display:none;font:400 20px/1.5 var(--serif);color:var(--ink)}
.lead-v strong{font-weight:600}
.fig-reshape[data-purpose=default] .lead-v[data-purpose=default],.fig-reshape[data-purpose=decide] .lead-v[data-purpose=decide],.fig-reshape[data-purpose=learn] .lead-v[data-purpose=learn],.fig-reshape[data-purpose=check] .lead-v[data-purpose=check]{display:block}
.rs-assume{margin:12px 0;padding-inline-start:12px;border-inline-start:3px solid var(--flag);font:14px/1.55 var(--sans);color:var(--ink-2)}
.rs-picture{margin:14px 0;padding:14px 0;border-block:1px solid var(--line)}
.mini-bar{display:flex;height:16px;border-radius:8px;overflow:hidden;background:var(--good)}
.mini-real{width:8.33%;background:var(--fault);transition:width .4s ease}
.mini-text{margin:8px 0 6px;font:600 15px var(--sans)}
.rs-dense{font:15.5px/1.75 var(--sans);color:var(--ink-2)}
.rs-row{border-top:1px solid var(--line);padding:11px 0}
.rs-row>summary{display:flex;align-items:center;gap:10px;font:600 15px var(--sans);color:var(--ink)}
.rs-row-body{padding:8px 0 2px;padding-inline-start:32px}
.rs-row-body p{font:15.5px/1.65 var(--sans)}
.rs-check{margin-top:12px;padding-top:14px;border-top:1px dashed var(--line-2)}
.rs-check>p:first-child{font:400 18px/1.5 var(--serif);margin-bottom:10px}
.rs-check-fb{margin-top:10px;font:15px/1.55 var(--sans)}
.js .fig-reshape .rs-lead,.js .fig-reshape .rs-assume,.js .fig-reshape .rs-rows,.js .fig-reshape .rs-purpose,.js .fig-reshape .rs-picture,.js .fig-reshape .rs-check{display:none}
.js .fig-reshape:not([data-step="0"]) .rs-lead{display:block}
.js .fig-reshape[data-step="2"] :is(.rs-assume,.rs-rows),.js .fig-reshape[data-step="3"] :is(.rs-assume,.rs-rows,.rs-purpose),.js .fig-reshape[data-step="4"] :is(.rs-assume,.rs-rows,.rs-purpose,.rs-picture),.js .fig-reshape[data-step="5"] :is(.rs-assume,.rs-rows,.rs-purpose,.rs-picture,.rs-check){display:block}
.js .fig-reshape:not([data-step="0"]):not([data-step="1"]) .rs-dense{display:none}
.js .fig-reshape[data-step="1"] .rs-dense{margin-top:12px;padding-top:12px;border-top:1px solid var(--line);color:var(--muted);font-size:14.5px}

.tests-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px;margin-top:16px}
.tcard{display:flex;flex-direction:column;gap:9px;border:1px solid var(--line);border-radius:14px;padding:16px 17px}
.tname{font:600 12px/1.3 var(--sans);letter-spacing:.09em;text-transform:uppercase;color:var(--accent)}
.tq{font:400 17px/1.55 var(--serif);color:var(--ink)}
.tprompt{font:600 14px var(--sans)}
.tcard .button{min-height:40px;padding:8px 15px;font-size:14.5px}
.tfb{font:14.5px/1.55 var(--sans);color:var(--ink-2)}
.tfb.right{color:var(--up)}
.tfb:empty{display:none}
.nojs-answer{font:14.5px/1.55 var(--sans);color:var(--ink-2)}
.tcard textarea{width:100%;min-height:76px;resize:vertical;padding:10px 12px;border:1px solid var(--line-2);border-radius:10px;font:15px/1.5 var(--sans);color:var(--ink);background:#fff}
.t-example>summary{display:inline-flex;align-items:center;gap:8px;font:600 14px var(--sans);color:var(--accent)}
.t-example p{font:14.5px/1.55 var(--sans);margin-top:8px}
.tcard.retain{border-style:dashed}
.tcard.retain p:last-child{font:14.5px/1.55 var(--sans);color:var(--ink-2)}

.references{margin-top:70px;border-top:1px solid var(--line);padding-top:30px;scroll-margin-top:76px}
.references>.eyebrow{margin-bottom:8px}
.references h2{font:500 32px/1.2 var(--serif)}
.references-intro{font:17px/1.7 var(--serif);color:var(--ink-2);margin-top:10px}
.source-list{list-style:none;padding:0;margin:22px 0 0}
.source{display:grid;grid-template-columns:30px minmax(0,1fr);gap:12px;padding:16px 0;border-top:1px solid var(--line);scroll-margin-top:84px}
.source:target{outline:2px solid #c7d4de;outline-offset:4px;border-radius:6px}
.source-number{font:600 13px var(--sans);color:var(--accent);padding-top:2px}
.source-authors{font:13px/1.6 var(--sans);color:var(--muted);margin-bottom:4px}
.source-title{display:inline-block;font:17.5px/1.5 'Source Serif',Georgia,serif;text-decoration:none;color:var(--ink);overflow-wrap:anywhere}
.source-title:hover{text-decoration:underline;color:var(--accent-ink)}
.source-detail{margin-top:8px}
.source-detail>summary{font:500 13px var(--sans);color:var(--accent);width:fit-content;padding:3px 0}
.source-detail>summary::before{content:'+';display:inline-block;margin-inline-end:7px}
.source-detail[open]>summary::before{content:'−'}
.source-detail p{font:14.5px/1.7 var(--sans);color:var(--ink-2);margin-top:6px}
.source-detail a{display:inline-block;font-size:13px;margin-top:6px}
.citation-popover{position:fixed;z-index:45;width:min(380px,calc(100vw - 28px));max-height:min(480px,calc(100dvh - 90px));overflow-y:auto;background:#fff;border:1px solid #c7d4de;border-radius:12px;box-shadow:0 14px 40px -12px rgba(20,40,60,.3);padding:18px 20px 14px}
.citation-close{position:absolute;inset-inline-end:8px;top:6px;display:grid;place-items:center;width:34px;height:34px;font-size:24px;color:var(--muted);border-radius:50%}
.citation-authors{font:13px/1.6 var(--sans);color:var(--muted);padding-inline-end:22px}
.citation-title{font:18px/1.45 'Source Serif',Georgia,serif;margin-top:8px;overflow-wrap:anywhere}
.citation-context{font:14px/1.7 var(--sans);margin-top:10px;color:var(--ink-2)}
.citation-links{display:flex;justify-content:space-between;gap:15px;padding-top:11px;border-top:1px solid var(--line);margin-top:13px;font:13px var(--sans)}
.citation-links a{text-decoration:none}
.author-note{display:flex;align-items:flex-start;gap:16px;border-top:1px solid var(--line);margin-top:26px;padding-top:24px}
.author-seal{width:38px;height:38px;flex-shrink:0;display:grid;place-items:center;border:1px solid #c8d7e2;color:var(--accent);border-radius:50%;font:24px/1 var(--serif)}
.author-note p{font:14px/1.75 var(--sans);color:var(--muted);margin-bottom:6px}
.author-note .author-name{font-weight:600;color:var(--ink)}
.site-footer{max-width:calc(var(--measure) + 40px);margin:40px auto 0;padding:22px 20px 30px;display:flex;justify-content:space-between;align-items:flex-start;gap:20px;border-top:1px solid var(--line)}
.footer-title{font-size:14px;text-decoration:none;color:var(--ink)}
.site-footer p{font-size:13px;color:var(--muted);margin-top:4px}
.footer-actions{display:flex;gap:16px;align-items:center;flex-wrap:wrap;font-size:13.5px}
.footer-actions button{color:var(--accent)}
.footer-actions a{text-decoration:none}
.toast{position:fixed;bottom:20px;left:50%;transform:translateX(-50%);z-index:60;background:#fff;border:1px solid #c5d3df;border-radius:8px;padding:12px 20px;font-size:14px;box-shadow:0 6px 24px rgba(30,60,90,.12);max-width:90vw}

.series-sidebar{display:flex;align-items:center;flex-wrap:wrap;gap:8px;margin-bottom:26px}
.series-sidebar>.eyebrow,.series-sidebar .sidebar-stats{display:none}
.series-sidebar>a{font-size:14px;text-decoration:none;padding:6px 12px;border:1px solid var(--line);border-radius:999px;color:var(--muted)}
.series-sidebar>a.selected{color:var(--accent);border-color:#c4d4e0}
.series-sidebar>a>span{font-size:12.5px;margin-inline-start:10px}
.index-intro{padding:0 0 28px}
.index-intro h1{font:430 48px/1.15 var(--serif);margin:8px 0 12px}
.index-deck{font:20px/1.7 var(--serif);color:var(--ink-2)}
.collection-heading{display:flex;justify-content:space-between;gap:20px;border-block:1px solid var(--line);padding:12px 0;margin-bottom:20px}
.collection-heading h2{font:600 14px var(--sans)}
.collection-heading>span{font-size:13px;color:var(--muted)}
.featured{padding:24px 26px;border:1px solid var(--line);border-radius:16px;background:#fff}
.featured-top{display:flex;align-items:center;gap:12px;flex-wrap:wrap;font-size:13px}
.featured-top time{color:var(--muted);margin-inline-start:auto}
.article-number{font:600 13px var(--sans);color:var(--accent)}
.featured h2{font:500 32px/1.25 var(--serif);margin:14px 0 12px;letter-spacing:-.015em}
.featured h2 a{text-decoration:none;color:var(--ink)}
.featured-copy>p{font:19px/1.65 var(--serif);color:var(--ink-2)}
.feature-bottom{display:flex;justify-content:space-between;gap:14px;align-items:center;flex-wrap:wrap;margin-top:20px;padding-top:14px;border-top:1px solid var(--line)}
.feature-meta{display:flex;align-items:center;gap:7px 16px;font-size:13px;color:var(--muted);flex-wrap:wrap}
.feature-meta>a{text-decoration:none}
.read-essay{font:600 15px var(--sans);text-decoration:none}
.series-about{padding:28px 0}
.series-about h2{font:500 26px/1.3 var(--serif);margin-bottom:10px}
.series-about p{font:18px/1.75 var(--serif);color:var(--ink-2)}

.mode-skim .expand-section{display:inline-flex}
.mode-skim .prose>:not(.fig){display:none}
.mode-skim .essay-section.expanded .prose>:not(.fig){display:revert}
.mode-skim .essay-section.expanded .prose>ol.principles{display:grid}
.mode-skim .prose{margin-top:18px}

@keyframes rise{from{opacity:0;translate:0 8px}}

html[lang=ar] body{font-family:var(--sans)}
html[lang=ar] .eyebrow,html[lang=ar] .section-tag,html[lang=ar] .fig-label,html[lang=ar] .short-version h2,html[lang=ar] .tname,html[lang=ar] .step-count,html[lang=ar] .felt-headrow .ch{letter-spacing:0;text-transform:none}
html[lang=ar] .fig-label,html[lang=ar] .short-version h2,html[lang=ar] .tname{font-size:13.5px}
html[lang=ar] .article-heading h1{font:400 clamp(40px,6.2vw,62px)/1.35 var(--serif);letter-spacing:0}
html[lang=ar] .article-heading h1 em{font-style:normal}
html[lang=ar] .hero-deck,html[lang=ar] .lede{font-style:normal}
html[lang=ar] .hero-deck{font-size:clamp(21px,2.6vw,25px);line-height:1.8}
html[lang=ar] .essay-section h2{font:400 clamp(30px,4vw,40px)/1.45 var(--serif);letter-spacing:0}
html[lang=ar] .lede{font-size:24px;line-height:1.8}
html[lang=ar] .prose>p,html[lang=ar] .prose li p{font-size:23.5px;line-height:2}
html[lang=ar] .principles li p{font-size:20.5px}
html[lang=ar] .takeaway{font:400 26px/1.7 var(--serif)}
html[lang=ar] .takeaway.final-thought{font-size:30px}
html[lang=ar] .short-list a{font-size:21px;line-height:1.75}
html[lang=ar] .fig-title{font:400 27px/1.45 var(--serif);letter-spacing:0}
html[lang=ar] .pz-text>p:first-child,html[lang=ar] .pz-q,html[lang=ar] .step-title,html[lang=ar] .z-prompts li,html[lang=ar] .tq,html[lang=ar] .rs-check>p:first-child,html[lang=ar] .lead-v{font-family:var(--serif);font-size:21px;line-height:1.75}
html[lang=ar] .pz-q{font-weight:400}
html[lang=ar] .references h2,html[lang=ar] .featured h2,html[lang=ar] .index-intro h1,html[lang=ar] .series-about h2{font-family:var(--serif);font-weight:400;letter-spacing:0;line-height:1.5}
html[lang=ar] .references-intro,html[lang=ar] .index-deck,html[lang=ar] .featured-copy>p,html[lang=ar] .series-about p{font-size:21px;line-height:1.85}
html[lang=ar] .source-title,html[lang=ar] .citation-title{font-family:'Source Serif',Georgia,serif}
html[lang=ar] .formula var{font-family:var(--sans)}
html[lang=ar] .short-list li::before{content:counter(s,arabic-indic)}
html[lang=ar] .principles li::before{content:counter(p,arabic-indic)}
html[lang=ar] .z-prompts,html[lang=ar] .z-how-list,html[lang=ar] .parts-static{list-style-type:arabic-indic}
html[dir=rtl] .source-title,html[dir=rtl] .citation-title{display:block;text-align:right}
html[dir=rtl] .source-authors,html[dir=rtl] .citation-authors{text-align:right}

@media (max-width:760px){
  .chapter-roadmap{grid-template-columns:repeat(2,minmax(0,1fr))}
  .chapter-roadmap a:nth-child(3){border-inline-start:0;padding-inline-start:0}
  .chapter-roadmap a:nth-child(n+3){border-top:1px solid var(--line)}
  .stepper .st{display:none}
  .stepper button{align-items:center;padding:8px}
  .cr-chart{grid-template-columns:minmax(0,1fr);gap:8px}
  .tests-grid{grid-template-columns:minmax(0,1fr)}
  .felt-row{grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:10px 14px}
  .felt-study{grid-column:1/-1}
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}
@media (max-width:560px){
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  .site-header{height:54px}
  .brand>span:last-child{font-size:13px}
  .research-essay,.series-dashboard{padding:26px 18px 0}
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  .takeaway.final-thought{font-size:24px}
  .essay-section h2{font-size:30px}
  .essay-section{padding-top:56px}
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  html[lang=ar] #the-gap .prose>p:first-child{font-size:24px}
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  .parts-counts dt{font-size:12px}
  .rs-card{padding:15px 14px}
  .scale button{width:38px;height:38px}
  .cr-val{font-size:14px}
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}
@media (prefers-reduced-motion:reduce){
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@media print{
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  a{color:inherit}
}