:root {
  color-scheme: light;
  --paper: #faf9f6; --surface: #fff; --ink: #242522; --body: #50514c;
  --muted: #70716a; --accent: #365f9e; --line: #dfdfd7; --wash: #f0efe9;
  --sans: -apple-system,BlinkMacSystemFont,'Helvetica Neue','PingFang SC','Microsoft YaHei',Arial,sans-serif;
  --serif: Georgia,'Times New Roman',serif;
  --mono: 'SFMono-Regular',Consolas,'Liberation Mono',monospace;
  --reading: 60rem; --figure: var(--reading); --gutter: 3rem;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 6rem; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 400 1.0625rem/1.8 var(--sans); -webkit-font-smoothing: antialiased; }
button,a { -webkit-tap-highlight-color: transparent; }
button { font: inherit; color: inherit; cursor: pointer; }
a { color: inherit; text-decoration: none; }
button:focus-visible,a:focus-visible,pre:focus-visible { outline: 2px solid var(--accent); outline-offset: 5px; }
img { display: block; max-width: 100%; height: auto; }
h1,h2,h3,p,figure,dl,dd { margin: 0; }
h1,h2,h3 { line-height: 1.25; letter-spacing: -.035em; text-wrap: balance; }
h2 { font-size: 2rem; font-weight: 550; } h3 { font-size: 1.0625rem; font-weight: 600; letter-spacing: -.015em; }
p { color: var(--body); text-wrap: pretty; } p+p { margin-top: 1.25rem; }
strong { color: var(--ink); font-weight: 600; }
.wide,.reading { width: min(var(--reading),calc(100% - var(--gutter))); margin-inline: auto; }
.eyebrow { color: var(--muted); font: 500 .6875rem/1.6 var(--sans); letter-spacing: .13em; text-transform: uppercase; }
.dot { margin-inline: .65rem; color: #b4b4aa; }
.keep-together { white-space: nowrap; }
.icon { width: 1.125rem; height: 1.125rem; fill: none; stroke: currentColor; stroke-width: 1.5; stroke-linecap: round; stroke-linejoin: round; }
.skip-link { position: fixed; left: 1rem; top: 1rem; padding: .5rem 1rem; background: var(--surface); transform: translateY(-200%); z-index: 100; }
.skip-link:focus { transform: none; } [hidden] { display: none!important; }

/* A quiet masthead, with color reserved for navigation and focus. */
.site-header { position: sticky; top: 0; z-index: 20; background: #faf9f6f5; border-bottom: 1px solid var(--line); backdrop-filter: blur(12px); }
.header-inner { min-height: 4.25rem; display: flex; justify-content: space-between; align-items: center; gap: 1.5rem; }
.brand { display: inline-flex; gap: .6rem; align-items: center; font-weight: 650; font-size: 1.1rem; letter-spacing: -.025em; }
.brand img { width: 1.65rem; height: 1.35rem; }
.header-controls { display: flex; gap: 2rem; align-items: center; min-width: 0; }
.site-header nav { display: flex; align-items: center; gap: 1.5rem; font-size: .8125rem; line-height: 1.5; }
.site-header nav a { padding-block: 1.45rem; position: relative; color: var(--muted); white-space: nowrap; }
.site-header nav a:hover,.site-header nav a[aria-current] { color: var(--ink); }
.site-header nav a[aria-current]::after { content: ''; position: absolute; height: 2px; background: var(--accent); bottom: -1px; left: 0; right: 0; }
.language-switch { display: inline-flex; gap: .125rem; flex-shrink: 0; }
.language-switch button { border: 0; border-radius: 3px; background: transparent; color: var(--muted); font-size: .75rem; line-height: 1.3; padding: .55rem .65rem; min-height: 2.25rem; }
.language-switch button[aria-pressed='true'] { background: var(--ink); color: var(--surface); }

/* The title reads as a paper title, not an oversized product logo. */
.hero { padding-block: 5.25rem 4.5rem; }
.hero .eyebrow { display: flex; align-items: center; }
.hero .eyebrow::before { content: ''; width: 1.5rem; height: 2px; margin-right: .75rem; background: var(--accent); flex-shrink: 0; }
.hero h1 { font: 400 clamp(2.35rem,4.5vw,3.25rem)/1.13 var(--serif); letter-spacing: -.045em; margin-top: 1.5rem; text-wrap: balance; }
.hero-wordmark { color: var(--ink); white-space: nowrap; } .paper-title-text { display: inline; }
.title-ending { display: block; }
.hero-deck { max-width: 40rem; margin-top: 1.75rem; font-size: 1.0625rem; line-height: 1.8; }
.resource-links { display: flex; flex-wrap: wrap; align-items: center; gap: .65rem; margin-top: 1.75rem; }
.resource-link { display: inline-flex; align-items: center; gap: .6rem; min-height: 2.75rem; padding: .6rem .9rem; border: 1px solid var(--line); border-radius: 4px; background: var(--surface); font-size: .8125rem; line-height: 1.4; font-weight: 500; transition: border-color .16s,background-color .16s; }
.resource-link:first-child { border-color: var(--ink); }
.resource-link:hover { border-color: var(--ink); background: var(--wash); }
.resource-link img { width: 1.125rem; height: 1.125rem; object-fit: contain; }
.resource-link::after { content: '↗'; font-size: .875rem; color: var(--muted); margin-left: .3rem; }

/* One reading grid and an understated section rhythm, instead of stacked cards. */
.introduction,.chapter { position: relative; padding-block: 4rem; }
.introduction::before,.chapter::before { content: ''; position: absolute; top: 0; left: 50%; width: min(var(--reading),calc(100% - var(--gutter))); transform: translateX(-50%); border-top: 1px solid var(--line); }
.introduction h2 { max-width: 33rem; margin-bottom: 1.25rem; }
.chapter-heading .chapter-marker { display: flex; align-items: center; gap: 1rem; color: var(--accent); font: 500 .6875rem/1.6 var(--mono); letter-spacing: .045em; margin-bottom: 1.2rem; }
.chapter-marker>span { color: var(--muted); font: 400 .75rem/1.6 var(--sans); letter-spacing: 0; }
.chapter-heading>p { margin-top: 1.25rem; }
.system-explorer { margin-top: 2.75rem; }
.explorer-topline { display: flex; justify-content: space-between; align-items: center; gap: 1rem; margin-bottom: 1rem; }
.explorer-hint { font-size: .75rem; color: var(--muted); }
.stage-tabs { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 1.5rem; }
.stage-tab { display: grid; grid-template-columns: auto 1fr; column-gap: .7rem; text-align: left; border: 0; border-bottom: 1px solid var(--line); border-radius: 0; background: transparent; padding: 1rem 0 1.15rem; }
.stage-tab:hover { border-bottom-color: var(--muted); }
.stage-tab[aria-selected='true'] { border-bottom: 2px solid var(--accent); padding-bottom: calc(1.15rem - 1px); }
.stage-index { grid-row: span 2; color: var(--muted); font: .6875rem/1.6 var(--mono); padding-top: .35rem; }
.stage-tab[aria-selected='true'] .stage-index { color: var(--accent); }
.stage-name { font: 400 1.5rem/1.3 var(--serif); letter-spacing: -.025em; }
.stage-note { color: var(--muted); font-size: .6875rem; line-height: 1.6; margin-top: .4rem; }
.stage-description { display: grid; grid-template-columns: 1fr auto; gap: 2rem; align-items: center; padding-top: 1.25rem; min-height: 6.5rem; }
.stage-description p { font-size: .875rem; line-height: 1.8; }
.stage-description a { color: var(--accent); font-size: .8125rem; white-space: nowrap; text-decoration: underline; text-underline-offset: .3em; text-decoration-color: #bac7d9; }

/* Complete paper artwork provides the page's color; never crop or stretch it. */
.paper-figure { width: min(var(--figure),calc(100% - var(--gutter))); margin: 2.25rem auto 0; }
.figure-image-link { display: block; background: var(--surface); padding: 1rem; border: 1px solid var(--line); border-radius: 3px; cursor: zoom-in; }
.paper-figure img { width: 100%; height: auto; object-fit: contain; }
.evolution-figure .figure-image-link { width: min(100%,34rem); margin-inline: auto; }
.figure-caption { display: flex; align-items: start; justify-content: space-between; gap: 1.5rem; padding-top: .65rem; }
.caption-text { color: var(--muted); font-size: .75rem; line-height: 1.75; padding-top: .4rem; }
.caption-text strong { font-weight: 500; }
.figure-expand { display: inline-flex; align-items: center; flex-shrink: 0; gap: .45rem; padding: .35rem .15rem; min-height: 2.25rem; border: 0; background: transparent; color: var(--muted); font-size: .75rem; line-height: 1.5; }
.figure-expand:hover { color: var(--accent); } .figure-expand .icon { width: 1rem; height: 1rem; }
.construction-copy { margin-top: 2rem; }
.construction-copy article { display: grid; grid-template-columns: 11rem 1fr; gap: 1.5rem; padding-block: 1.25rem; border-bottom: 1px solid var(--line); }
.construction-copy article:first-child { padding-top: 0; }
.construction-copy article:last-of-type { border-bottom: 0; }
.construction-copy h3 { padding-top: .25rem; }
.construction-copy article p { font-size: .9375rem; line-height: 1.8; }
.stat-line { display: grid; grid-template-columns: repeat(4,minmax(0,1fr)); margin-top: 1.75rem; padding-block: 1.5rem; border-block: 1px solid var(--line); gap: 1.25rem; }
.stat-line>div { display: flex; flex-direction: column-reverse; justify-content: flex-end; }
.stat-line dt { font-size: .75rem; color: var(--muted); margin-top: .25rem; }
.stat-line dd { font-size: 1.9rem; font-weight: 500; line-height: 1.3; letter-spacing: -.045em; font-variant-numeric: tabular-nums; }
.training-notes { margin-top: 1.75rem; }
.training-notes article { padding-block: 1.5rem; border-bottom: 1px solid var(--line); }
.training-notes article:last-child { border-bottom: 0; }
.training-notes article>div { display: flex; align-items: baseline; gap: 1rem; margin-bottom: .65rem; }
.training-notes .eyebrow { min-width: 6rem; color: var(--accent); font-family: var(--mono); letter-spacing: .025em; }
.training-notes article p { margin-left: 7rem; font-size: .9375rem; }
.runtime { width: 100%; margin-top: 2rem; }
.runtime-top { width: min(var(--reading),calc(100% - var(--gutter))); margin-inline: auto; border-top: 1px solid var(--line); padding-top: 2.5rem; }
.runtime-top h3 { font-size: 1.625rem; font-weight: 550; margin: .75rem 0 1rem; letter-spacing: -.025em; }
.runtime-top .eyebrow { color: var(--accent); }
.result-highlight { margin-top: 2rem; padding-block: 1.5rem; border-block: 1px solid var(--line); }
.result-highlight dl { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 1.5rem; margin-top: 1rem; }
.result-highlight dl>div { display: flex; flex-direction: column-reverse; }
.result-highlight dt { color: var(--muted); font-size: .8125rem; margin-top: .2rem; }
.result-highlight dd { font-size: 2.25rem; color: var(--ink); line-height: 1.3; font-weight: 500; letter-spacing: -.04em; font-variant-numeric: tabular-nums; }
.result-highlight dd>span { color: var(--muted); font-size: .75rem; font-weight: 400; letter-spacing: 0; padding-left: .4rem; }
.results-copy { margin-top: 1.5rem; font-size: .9375rem; }
.closing { padding-block: 3.5rem; border-top: 1px solid var(--line); }
.closing h2 { margin-top: .75rem; }
.hero-links { display: flex; flex-wrap: wrap; gap: 1.5rem; margin-top: 1.25rem; color: var(--accent); font-size: .875rem; }
.hero-links a { text-decoration: underline; text-underline-offset: .3em; text-decoration-color: #bac7d9; }
.citation { margin-top: 2rem; }
.citation-heading { display: flex; justify-content: space-between; align-items: center; gap: 1rem; padding: .9rem 1.25rem; background: var(--wash); border: 1px solid var(--line); border-bottom: 0; border-radius: 3px 3px 0 0; font-size: .75rem; }
.citation-heading button { border: 1px solid #cbcbc2; background: var(--paper); border-radius: 3px; padding: .4rem .75rem; min-height: 2.25rem; font-size: .75rem; }
.citation-heading button:hover { border-color: var(--ink); }
.citation pre { background: var(--wash); border: 1px solid var(--line); border-top: 0; border-radius: 0 0 3px 3px; padding: 0 1.25rem 1.25rem; font: .75rem/1.85 var(--mono); white-space: pre-wrap; overflow-wrap: anywhere; margin: 0; color: var(--body); }
.copy-status { min-height: 1.5rem; font-size: .75rem; color: var(--accent); margin-top: .5rem; }
.site-footer { padding-block: 1.75rem; border-top: 1px solid var(--line); display: flex; justify-content: space-between; gap: 1rem; font-size: .6875rem; color: var(--muted); }
.site-footer div { display: flex; gap: 1.25rem; } .site-footer a:hover { color: var(--ink); }

/* Full-resolution figure viewer. */
dialog { width: min(94vw,96rem); max-width: 94vw; max-height: 94dvh; padding: 0; border: 1px solid var(--line); border-radius: 4px; background: var(--surface); color: var(--ink); overflow: hidden; }
dialog::backdrop { background: #242522bd; backdrop-filter: blur(4px); }
.dialog-toolbar { display: flex; justify-content: space-between; align-items: center; gap: 1rem; padding: .85rem 1.25rem; border-bottom: 1px solid var(--line); }
.dialog-toolbar h2 { font-size: 1rem; letter-spacing: -.01em; }
.dialog-toolbar>div { display: flex; align-items: center; gap: .5rem; flex-shrink: 0; }
.dialog-toolbar button { min-height: 2.5rem; border: 1px solid var(--line); background: var(--surface); border-radius: 3px; padding: .4rem .75rem; font-size: .875rem; }
#figure-close { display: inline-flex; justify-content: center; align-items: center; width: 2.5rem; }
.dialog-image-area { overflow: auto; max-height: calc(94dvh - 8rem); overscroll-behavior: contain; padding: 1.5rem; }
.dialog-image-area img { width: 100%; max-width: none; height: auto; }
.dialog-image-area.is-zoomed img { width: auto; max-width: none; }
.dialog-hint { padding: .7rem 1.25rem; border-top: 1px solid var(--line); font-size: .8125rem; color: var(--muted); }
body.dialog-open { overflow: hidden; }
html[lang='zh-CN'] h1,html[lang='zh-CN'] h2,html[lang='zh-CN'] h3 { letter-spacing: -.025em; }
html[lang='zh-CN'] .hero h1 { font-family: var(--sans); font-size: clamp(2rem,4.3vw,2.8rem); font-weight: 550; line-height: 1.4; }
html[lang='zh-CN'] .paper-title-text { white-space: pre-line; }
html[lang='zh-CN'] .introduction h2 { white-space: pre-line; }
html[lang='zh-CN'] .stage-name { font: 500 1.25rem/1.4 var(--sans); }

@media(max-width:900px) {
  .header-controls { gap: 1.25rem; } .site-header nav { gap: 1rem; }
  .hero { padding-top: 4rem; }
  .title-ending { display: inline; }
  .stage-description { grid-template-columns: 1fr; gap: .6rem; min-height: 8rem; }
  .stage-description a { justify-self: start; }
}
@media(max-width:680px) {
  :root { --gutter: 2.5rem; }
  html { scroll-padding-top: 8.5rem; } body { font-size: 1rem; line-height: 1.85; }
  .header-inner { flex-wrap: wrap; gap: 0; padding-top: .55rem; }
  .header-controls { display: contents; }
  .site-header nav { order: 3; width: 100%; gap: .25rem; justify-content: space-between; overflow-x: auto; scrollbar-width: none; margin-top: .25rem; }
  .site-header nav a { padding-block: .8rem; font-size: .75rem; min-height: 2.75rem; }
  .site-header nav::-webkit-scrollbar { display: none; } .language-switch { margin-left: auto; }
  .hero { padding-block: 2.75rem 3rem; }
  .hero .eyebrow { font-size: .625rem; letter-spacing: .075em; }
  .hero h1 { font-size: clamp(2rem,7.6vw,2.85rem); line-height: 1.16; letter-spacing: -.04em; margin-top: 1.2rem; }
  .hero-deck { font-size: .9375rem; margin-top: 1.25rem; }
  .resource-links { gap: .5rem; margin-top: 1.5rem; }
  .resource-link { padding-inline: .65rem; font-size: .75rem; gap: .4rem; }
  .resource-link img { width: 1rem; height: 1rem; } .resource-link::after { display: none; }
  .introduction,.chapter { padding-block: 3rem; } h2 { font-size: 1.65rem; } h3 { font-size: 1rem; }
  .chapter-heading .chapter-marker { gap: .75rem; margin-bottom: 1rem; }
  .chapter-marker>span { font-size: .6875rem; }
  .system-explorer { margin-top: 2rem; } .explorer-hint { display: none; }
  .stage-tabs { gap: 1rem; } .stage-tab { display: block; padding-top: .5rem; }
  .stage-index { display: block; padding: 0; margin-bottom: .3rem; }
  .stage-name { font-size: 1.375rem; } .stage-note { display: none; }
  .stage-description { padding-top: 1rem; min-height: 8.25rem; }
  .paper-figure { margin-top: 1.75rem; } .figure-image-link { padding: .5rem; }
  .figure-caption { gap: .65rem; } .caption-text { font-size: .6875rem; }
  .figure-expand>span { display: none; } .figure-expand { min-width: 2.5rem; min-height: 2.5rem; justify-content: flex-end; }
  .construction-copy article { grid-template-columns: 1fr; gap: .5rem; }
  .construction-copy article p { font-size: .9375rem; }
  .stat-line { grid-template-columns: repeat(2,minmax(0,1fr)); gap: 1.25rem 1.5rem; }
  .stat-line dd { font-size: 1.8rem; }
  .training-notes article>div { display: block; } .training-notes h3 { margin-top: .4rem; }
  .training-notes article p { margin-left: 0; } .runtime-top h3 { font-size: 1.45rem; }
  .result-highlight dl { gap: .75rem; } .result-highlight dd { font-size: clamp(1.5rem,6vw,1.8rem); }
  .result-highlight dd>span { padding-left: .2rem; font-size: .625rem; } .result-highlight dt { font-size: .6875rem; }
  .closing { padding-block: 2.5rem; } .citation-heading { padding-inline: 1rem; }
  .citation pre { padding-inline: 1rem; font-size: .6875rem; white-space: pre; overflow-wrap: normal; overflow-x: auto; }
  .site-footer { flex-direction: column; gap: .75rem; padding-block: 1.5rem; }
  .dialog-toolbar { padding: .75rem; } .dialog-toolbar h2 { font-size: .875rem; }
  .dialog-toolbar button { font-size: .8125rem; } .dialog-image-area { padding: .5rem; }
  html[lang='zh-CN'] .hero h1 { font-size: clamp(1.75rem,6.9vw,2.3rem); }
}
@media(prefers-reduced-motion:reduce) {
  html { scroll-behavior: auto; } *,*::before,*::after { animation: none!important; transition: none!important; }
}
@media print {
  body { background: #fff; }
  .site-header,.resource-links,.figure-expand,dialog,.stage-tabs { display: none!important; }
  .hero,.chapter,.introduction { padding-block: 1.5rem; }
  .wide,.reading,.paper-figure { width: 100%; } .paper-figure { break-inside: avoid; }
  .figure-image-link { border: 0; padding: 0; }
}