:root {
  color-scheme: light;
  --paper: #faf8f3;
  --surface: #ffffff;
  --well: #eef2f3;
  --ink: #0b1520;
  --body: #1f2e3b;
  --green: #124563;
  --green-dark: #0a2f46;
  --soft-green: #e6eef2;
  --line: #b8c4ca;
  --muted: #394a58;
  --amber: #c87312;
  --amber-ink: #6e3b00;
  --amber-soft: #fef7ea;
  --serif: Georgia, 'Times New Roman', serif;
  --sans: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Inter', 'Segoe UI', sans-serif;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 108px; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--sans); font-size: 16px; line-height: 1.65; -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility; }
body:has(dialog[open]) { overflow: hidden; }
button, textarea { font: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
a { color: inherit; text-decoration: none; }
button { color: inherit; cursor: pointer; }
button:disabled { cursor: default; }
button, a, textarea { outline-offset: 4px; }
:focus-visible { outline: 2px solid var(--green); }
button { touch-action: manipulation; }
::selection { background: #cfe0e8; color: var(--ink); }
[hidden] { display: none !important; }
.container { width: min(1320px, calc(100% - 96px)); margin-inline: auto; }
.skip-link { position: fixed; z-index: 100; top: -70px; left: 24px; background: var(--green); color: white; padding: 14px 20px; border-radius: 6px; font-weight: 600; }
.skip-link:focus { top: 14px; }
.site-header { position: sticky; z-index: 20; top: 0; background: rgba(250,248,243,.95); backdrop-filter: blur(18px); border-bottom: 1px solid var(--line); }
.header-inner { height: 84px; display: flex; justify-content: space-between; align-items: center; }
.wordmark { display: inline-flex; gap: 6px; align-items: center; font-size: 29px; letter-spacing: -1.1px; font-weight: 650; color: var(--ink); white-space: nowrap; }
.wordmark-ai { font-weight: 450; }
.brand-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--amber); align-self: start; margin-top: 8px; margin-left: 1px; }
.site-nav { display: flex; align-items: center; gap: 32px; font-size: 15px; font-weight: 500; color: var(--ink); margin-left: auto; margin-right: 28px; }
.site-nav a { padding-block: 12px; transition: color .15s; }
.site-nav a:hover, .site-nav a[aria-current] { color: var(--green); }
.site-nav a[aria-current] { text-decoration: underline; text-decoration-color: var(--amber); text-decoration-thickness: 2px; text-underline-offset: 7px; font-weight: 600; }
.nav-contact { border-left: 1px solid var(--line); padding-left: 26px; }
.nav-contact span { margin-left: 8px; }
.header-tools { display: flex; align-items: center; gap: 14px; }
.lang-switch { display: inline-flex; align-items: center; gap: 2px; border: 1px solid #9fb0b9; border-radius: 999px; padding: 3px; background: #eaeef0; font-size: 13px; line-height: 1; }
.lang-btn { border: 0; background: transparent; color: var(--body); padding: 6px 12px; border-radius: 999px; font-size: 13px; font-weight: 600; line-height: 1; transition: background .15s, color .15s, box-shadow .15s; }
.lang-btn:hover { color: var(--ink); }
.lang-btn.is-active, .lang-btn[aria-pressed="true"] { background: var(--ink); color: #fff; box-shadow: 0 1px 3px rgba(11,21,32,.18); }
.lang-sep { display: none; }
.menu-toggle { display: none; }
.eyebrow, .micro-label, .card-eyebrow, .section-index { font-size: 12.5px; letter-spacing: 1.2px; font-weight: 600; text-transform: uppercase; }
.eyebrow { display: flex; align-items: center; gap: 9px; margin: 0 0 22px; color: var(--green); line-height: 1.6; }
.tiny-dot { display: inline-block; width: 6px; height: 6px; background: var(--amber); border-radius: 50%; flex: 0 0 auto; }
.positioning { margin: 0 0 18px; font-size: 16px; line-height: 1.7; color: var(--body); }
h1, h2, h3, p { margin-top: 0; }
h1 { font-family: var(--serif); font-size: clamp(50px, 5vw, 76px); line-height: 1.06; letter-spacing: -2.4px; font-weight: 400; color: var(--ink); margin-bottom: 24px; }
h1 em, h2 em { font-weight: 400; color: var(--green); }
.button { min-height: 48px; border-radius: 6px; border: 1px solid transparent; padding: 13px 22px; display: inline-flex; justify-content: center; align-items: center; gap: 16px; font-size: 14.5px; font-weight: 600; line-height: 1.4; transition: background .18s, transform .18s, border-color .18s; }
.button-primary { background: var(--green); color: white; box-shadow: 0 2px 6px rgba(18,69,99,.18); }
.button-primary:hover { background: var(--green-dark); }
.button span:last-child { font-size: 16px; font-weight: 400; }
.text-link { display: inline-flex; gap: 12px; align-items: center; font-size: 14.5px; font-weight: 600; color: var(--green); padding-block: 10px; }
.text-link:hover { color: var(--green-dark); text-decoration: underline; text-underline-offset: 4px; }
.figure-topline { display: flex; gap: 10px; justify-content: space-between; align-items: center; padding-inline: 8px; }
.micro-label { color: var(--green); font-size: 12px; letter-spacing: 1.1px; line-height: 1.5; font-weight: 600; }
.concept-tag { border: 1px solid var(--line); border-radius: 30px; font-size: 12px; padding: 5px 10px; color: var(--muted); white-space: nowrap; }
.section { padding-block: 96px; }
.section-index { display: flex; align-items: center; gap: 14px; color: var(--green); margin-bottom: 32px; }
.section-index > span { color: var(--amber-ink); font-size: 13px; font-weight: 700; font-variant-numeric: tabular-nums; }
h2 { font-family: var(--serif); font-size: clamp(36px, 3.5vw, 52px); line-height: 1.14; letter-spacing: -1.4px; font-weight: 400; color: var(--ink); margin-bottom: 24px; }
.section-lead { font-size: 21px; line-height: 1.62; color: var(--ink); margin-bottom: 20px; }
.body-copy { font-size: 16.5px; line-height: 1.78; color: var(--body); max-width: 600px; margin-bottom: 18px; }
.card-eyebrow { display: flex; gap: 8px; align-items: center; color: var(--green); font-size: 12px; letter-spacing: 1.1px; font-weight: 600; }
.section-investigation { background: var(--well); border-block: 1px solid var(--line); padding-bottom: 90px; }
.investigation-intro { display: grid; grid-template-columns: 1.25fr .75fr; gap: 60px; align-items: end; margin-bottom: 36px; }
.investigation-intro h2 { margin-bottom: 0; }
.investigation-intro .body-copy { font-size: 16px; margin-bottom: 2px; }
.concept-shell { border: 1px solid #96a8b2; border-radius: 8px; background: var(--surface); box-shadow: 0 14px 36px rgba(11,21,32,.06); overflow: hidden; }
.concept-topline { display: flex; align-items: center; justify-content: space-between; gap: 15px; padding: 18px 28px; border-bottom: 1px solid var(--line); background: #f5f7f8; }
.concept-record { font-size: 13px; font-weight: 500; color: var(--muted); }
.concept-question { padding: 24px 28px; }
.concept-question p { font-family: var(--serif); font-size: 26px; line-height: 1.38; color: var(--ink); margin: 8px 0 0; letter-spacing: -.3px; }
.step-nav { display: grid; grid-template-columns: repeat(6, 1fr); padding-inline: 28px; border-block: 1px solid var(--line); background: #f8fafb; gap: 10px; }
.step-nav button { display: flex; gap: 9px; align-items: center; border: 0; border-bottom: 3px solid transparent; padding: 16px 6px; background: none; color: var(--muted); font-size: 14.5px; font-weight: 500; text-align: left; transition: color .15s, background .15s; }
.step-nav button > span { font-size: 12px; font-weight: 700; color: var(--amber-ink); font-variant-numeric: tabular-nums; }
.step-nav button:hover { color: var(--ink); background: rgba(18,69,99,.04); }
.step-nav button[aria-pressed="true"] { color: var(--ink); border-color: var(--amber); font-weight: 600; background: rgba(18,69,99,.06); }
.concept-content { display: grid; grid-template-columns: 1.55fr 1fr; }
.concept-scene { padding: 26px 28px 22px; background: var(--well); }
.scene-caption { display: flex; justify-content: space-between; gap: 12px; align-items: center; }
.scene-state { font-size: 12.5px; font-weight: 600; color: var(--amber-ink); background: var(--amber-soft); border: 1px solid #d4a55d; border-radius: 30px; padding: 5px 12px; }
.desktop-concept { margin-block: 16px; min-height: 294px; display: flex; align-items: center; }
.desktop-concept svg { width: 100%; height: auto; overflow: visible; }
.diagram-kicker { font: 600 11.5px var(--sans); letter-spacing: .8px; fill: var(--green); }
.diagram-label { font: 500 14px var(--sans); fill: var(--ink); }
.diagram-small { font: 500 12.5px var(--sans); fill: var(--body); }
.diagram-muted { opacity: .55; }
.diagram-highlight { stroke: var(--green); stroke-width: 2; }
.concept-connector { fill: none; stroke: #2b5b75; stroke-width: 1.6; }
.concept-connector--gap { stroke: var(--amber); stroke-dasharray: 5 5; }
.concept-shell.is-playing .active-connector { stroke-dasharray: 6 4; animation: flow-path 1.8s linear infinite; }
@keyframes flow-path { to { stroke-dashoffset: -20; } }
.scene-key { display: flex; gap: 22px; flex-wrap: wrap; font-size: 13px; font-weight: 500; color: var(--body); }
.scene-key span { display: flex; align-items: center; gap: 8px; }
.scene-key i { display: inline-block; width: 20px; height: 2px; background: var(--green); }
.scene-key .key-dashed { height: 0; border-top: 2px dashed var(--amber); background: none; }
.concept-explanation { padding: 28px; border-left: 1px solid var(--line); background: var(--surface); display: flex; flex-direction: column; }
.step-detail { border-left: 3px solid var(--green); background: #f1f5f7; border-radius: 0 4px 4px 0; padding: 12px 16px; color: var(--body); font-size: 14.5px; line-height: 1.72; }
.step-detail-gap { border-left: 3px dashed var(--amber); background: var(--amber-soft); color: var(--amber-ink); }
.basis-button { background: #f4f7f9; border: 1px solid #9fb0b9; border-radius: 6px; text-align: left; padding: 13px 16px; margin-top: 22px; font-size: 14px; font-weight: 600; color: var(--green); display: flex; justify-content: space-between; align-items: center; gap: 12px; width: 100%; transition: background .15s, border-color .15s; }
.basis-button:hover { background: var(--soft-green); border-color: var(--green); }
.concept-controls { border-top: 1px solid var(--line); padding: 18px 28px; background: #f8fafb; display: flex; justify-content: space-between; align-items: center; gap: 20px; }
.playback-controls { display: flex; align-items: center; gap: 10px; }
.concept-play { padding: 10px 18px; min-height: 44px; min-width: 152px; gap: 12px; font-size: 14px; font-weight: 600; }
.button .play-icon { font-size: 16px; }
.button [data-play-label] { font-size: 14px; }
.step-control { width: 44px; height: 44px; border: 1px solid #96a8b2; border-radius: 6px; background: var(--surface); color: var(--ink); font-size: 18px; font-weight: 600; }
.step-control:hover { background: var(--soft-green); border-color: var(--green); }
.step-control:disabled { opacity: .38; }
.replay-button { padding: 10px 14px; background: none; border: 1px solid transparent; border-radius: 6px; font-size: 14px; font-weight: 600; color: var(--body); }
.replay-button:hover { background: var(--soft-green); color: var(--ink); }
.playback-state { font-size: 13.5px; font-weight: 500; color: var(--muted); margin: 0; text-align: right; }
.concept-footnote { font-size: 13px; line-height: 1.7; margin: 0; padding: 14px 28px 20px; background: #f8fafb; border-top: 1px solid #e1e7ea; color: var(--muted); }
.mobile-concept { display: none; }
.site-footer { border-top: 1px solid var(--line); background: #f3f1ea; }
.footer-inner { min-height: 96px; display: flex; align-items: center; justify-content: space-between; gap: 20px; }
.site-footer .wordmark { font-size: 24px; }
.site-footer .brand-dot { margin-top: 6px; width: 6px; height: 6px; }
.site-footer p { margin: 0; font-size: 14px; color: var(--body); }
.footer-domain, .back-top { font-size: 14px; font-weight: 600; color: var(--green); }
.footer-domain:hover, .back-top:hover { color: var(--ink); text-decoration: underline; text-underline-offset: 4px; }
.footer-domain span { color: inherit; margin-left: 7px; }
.site-dialog { width: min(760px, calc(100% - 36px)); max-height: min(88vh, 880px); margin: auto; border: 1px solid #8ea3af; border-radius: 10px; background: var(--surface); padding: 30px 34px 34px; color: var(--ink); box-shadow: 0 24px 60px rgba(11,21,32,.22); overflow-y: auto; }
.site-dialog::backdrop { background: rgba(11,21,32,.55); backdrop-filter: blur(5px); }
.dialog-header { display: flex; align-items: center; justify-content: space-between; margin-bottom: 22px; padding-bottom: 14px; border-bottom: 1px solid var(--line); }
.dialog-close { border: 1px solid #96a8b2; background: #f4f7f9; color: var(--ink); font-size: 22px; font-weight: 400; border-radius: 50%; width: 38px; height: 38px; display: inline-flex; align-items: center; justify-content: center; }
.dialog-close:hover { background: var(--soft-green); border-color: var(--green); }
.site-dialog h2 { font-size: 32px; margin-bottom: 14px; color: var(--ink); }
.dialog-lead { font-size: 15px; line-height: 1.75; color: var(--body); }
.basis-records { margin: 22px 0 0; }
.basis-records > div { border-top: 1px solid var(--line); padding: 16px 0; }
.basis-records dt { font-size: 14px; font-weight: 600; color: var(--ink); margin-bottom: 8px; }
.basis-records dd { margin: 0; font-size: 15px; line-height: 1.75; color: var(--body); }

@media (max-width: 1150px) {
  .container { width: calc(100% - 64px); }
  h1 { font-size: 58px; letter-spacing: -2px; }
  .investigation-intro { gap: 40px; }
  .concept-content { grid-template-columns: 1.38fr 1fr; }
  .step-nav { gap: 6px; }
  .step-nav button { font-size: 13.5px; gap: 6px; }
}
@media (max-width: 850px) {
  .site-nav { gap: 20px; font-size: 14px; }
  .nav-contact { padding-left: 18px; }
  h1 { font-size: clamp(46px, 7.5vw, 68px); }
  .section { padding-block: 72px; }
  h2 { font-size: 36px; }
  .investigation-intro { grid-template-columns: 1fr; gap: 20px; }
  .investigation-intro .body-copy { max-width: 620px; }
  .concept-content { grid-template-columns: 1fr; }
  .concept-explanation { border-left: 0; border-top: 1px solid var(--line); padding: 24px; }
  .desktop-concept { min-height: 0; }
  .concept-scene { padding: 24px; }
  .playback-state { max-width: 240px; }
}
@media (max-width: 600px) {
  html { scroll-padding-top: 82px; }
  .container { width: calc(100% - 36px); }
  .header-inner { height: 72px; }
  .wordmark { font-size: 25px; }
  .brand-dot { margin-top: 6px; }
  .js .menu-toggle { display: flex; background: transparent; border: 0; padding: 10px 0 10px 12px; align-items: center; gap: 10px; font-size: 14px; font-weight: 600; color: var(--ink); }
  .menu-lines { position: relative; width: 18px; height: 10px; border-block: 2px solid var(--ink); }
  .js .site-nav { position: absolute; left: 0; right: 0; top: 72px; padding: 20px; background: var(--surface); border-bottom: 1px solid var(--line); box-shadow: 0 16px 28px rgba(11,21,32,.1); display: none; flex-direction: column; align-items: stretch; gap: 6px; margin: 0; }
  .js .site-nav.is-open { display: flex; }
  .site-nav a { padding: 13px 0; font-size: 16px; }
  .site-nav .nav-contact { border-left: 0; border-top: 1px solid var(--line); margin-top: 8px; padding-top: 16px; padding-left: 0; }
  body:not(.js) .site-nav { display: flex; flex-wrap: wrap; gap: 10px; font-size: 13px; }
  .section { padding-block: 58px; }
  .section-index { font-size: 12px; margin-bottom: 24px; gap: 12px; }
  h2 { font-size: 32px; letter-spacing: -1px; line-height: 1.18; margin-bottom: 20px; }
  .section-lead { font-size: 19px; line-height: 1.65; }
  .body-copy { font-size: 15.5px; line-height: 1.75; }
  .concept-topline { padding: 16px 18px; flex-direction: column; align-items: start; gap: 8px; }
  .concept-record { font-size: 12px; }
  .concept-question { padding: 20px 18px; }
  .concept-question p { font-size: 22px; line-height: 1.4; }
  .step-nav { padding-inline: 14px; gap: 4px; grid-template-columns: repeat(3, 1fr); }
  .step-nav button { flex-direction: row; gap: 6px; align-items: center; padding: 12px 6px; font-size: 13px; }
  .step-nav button > span { font-size: 11px; }
  .concept-scene { padding: 20px 18px; }
  .scene-caption { align-items: start; }
  .scene-state { font-size: 11.5px; }
  .desktop-concept { display: none; }
  .mobile-concept { display: block; margin-block: 20px; }
  .mobile-concept > div { padding: 14px 16px; border: 1px solid #9fb0b9; border-radius: 6px; background: var(--surface); }
  .mobile-concept strong { display: block; font-size: 14.5px; line-height: 1.6; font-weight: 500; color: var(--ink); margin-top: 4px; }
  .mobile-concept .mobile-gap { border: 1.5px dashed var(--amber); background: var(--amber-soft); }
  .mobile-gap .micro-label { color: var(--amber-ink); }
  .mobile-connector { display: block; text-align: center; color: var(--green); font-size: 18px; line-height: 1.6; }
  .scene-key { font-size: 12px; gap: 14px; }
  .concept-explanation { padding: 22px 18px; }
  .step-detail { font-size: 14px; }
  .concept-controls { padding: 16px 18px; flex-wrap: wrap; gap: 14px; }
  .playback-controls { gap: 8px; }
  .concept-play { min-width: 132px; padding-inline: 14px; }
  .step-control { width: 40px; height: 40px; }
  .playback-state { max-width: none; text-align: left; font-size: 12.5px; }
  .concept-footnote { padding-inline: 18px; font-size: 12px; }
  .footer-inner { padding-block: 24px; min-height: 0; display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
  .footer-inner .wordmark { font-size: 22px; }
  .footer-inner p { grid-row: 2; grid-column: 1 / -1; font-size: 13px; }
  .back-top { grid-row: 3; grid-column: 1 / -1; font-size: 13px; }
  .site-dialog { padding: 22px 18px; width: calc(100% - 24px); }
  .site-dialog h2 { font-size: 26px; }
  .header-tools { gap: 10px; }
  .lang-btn { padding: 5px 10px; font-size: 12px; }
}
html[lang^="zh"] {
  --serif: 'Songti SC', 'STSong', 'Noto Serif CJK SC', 'Source Han Serif SC', Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Noto Sans CJK SC', sans-serif;
}
html[lang^="zh"] h1 { font-size: clamp(42px, 4.3vw, 62px); line-height: 1.22; letter-spacing: -0.5px; font-weight: 600; }
html[lang^="zh"] h1 em, html[lang^="zh"] h2 em { font-style: normal; font-weight: 600; color: var(--green); }
html[lang^="zh"] h2 { font-size: clamp(32px, 3.2vw, 46px); line-height: 1.25; letter-spacing: -0.3px; font-weight: 600; }
html[lang^="zh"] .eyebrow, html[lang^="zh"] .micro-label, html[lang^="zh"] .card-eyebrow, html[lang^="zh"] .section-index { letter-spacing: 1px; font-size: 13px; }
html[lang^="zh"] .concept-question p { font-size: 24px; line-height: 1.45; font-weight: 600; letter-spacing: 0; }
@media (max-width: 600px) {
  html[lang^="zh"] h1 { font-size: clamp(34px, 8.8vw, 46px); line-height: 1.24; letter-spacing: -0.3px; }
  html[lang^="zh"] h2 { font-size: 30px; line-height: 1.28; letter-spacing: -0.2px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
}