:root {
  --bg: #FFFFFF;
  --bg-panel: #F5F6F8;
  --bg-panel-2: #ECEEF2;
  --border: #DDE1E8;
  --border-strong: #C6CBD4;
  --accent: #1D3F9A;
  --accent-dark: #0D2257;
  --text: #1E2127;
  --text-muted: #5B6270;
  --success: #1F6B4E;
  --warn: #E9B92F;
  --error: #C4372F;
  --on-dark: #FFFFFF;
  --on-dark-soft: #BCC6E2;
  --on-dark-mute: #8E9BC4;
  --on-dark-edge: rgba(255, 255, 255, .72);
  --on-dark-line: rgba(255, 255, 255, .26);
  --on-dark-hair: rgba(255, 255, 255, .14);
  --on-dark-fill: rgba(255, 255, 255, .08);
  --on-dark-fill-2: rgba(255, 255, 255, .16);
  --veil: rgba(13, 34, 87, .4);
  --clear: transparent;
  --font-display: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --fs-micro: 10.5px;
  --fs-code: 11px;
  --fs-caption: 11.5px;
  --fs-xs: 12px;
  --fs-small: 12.5px;
  --fs-ui: 13px;
  --fs-label: 14px;
  --fs-nav-small: 14.5px;
  --fs-nav: 15px;
  --fs-mobile-body: 15.5px;
  --fs-body: 16px;
  --fs-fact: 16.5px;
  --fs-lede: 17px;
  --fs-subtitle: 20px;
  --fs-brand: 19px;
  --fs-h1: clamp(34px, 3.4vw, 48px);
  --fs-h2: clamp(26px, 2.7vw, 36px);
  --fs-h3: 22px;
  --fs-mobile-h1: clamp(24px, 7vw, 30px);
  --weight-normal: 400;
  --weight-medium: 500;
  --weight-ui: 550;
  --weight-semibold: 600;
  --weight-strong: 650;
  --weight-bold: 700;
  --weight-display: 800;
  --tracking-title: -.025em;
  --tracking-cjk: -.02em;
  --tracking-brand: -.015em;
  --tracking-tight: -.01em;
  --tracking-button: -.005em;
  --tracking-mono: .03em;
  --tracking-label: .04em;
  --r-hero: 32px;
  --r-plate: 28px;
  --r-card: 20px;
  --r-item: 14px;
  --r-inset: 12px;
  --r-field: 8px;
  --r-pill: 999px;
  --r-round: 50%;
  --frame: 1312px;
  --reading-frame: 1120px;
  --header-frame: 1280px;
  --gutter: 64px;
  --nav-h: 76px;
  --hero-h: 700px;
  --section-gap: 88px;
  --ease: .18s ease;
  --reveal-time: .5s;
  --focus-width: 2px;
  --focus-offset: 3px;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: 24px; }
html.nav-open { overflow: hidden; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
[hidden] { display: none !important; }
img, svg { display: block; max-width: 100%; }
img { height: auto; }
button, input, select, textarea { font: inherit; }
button, summary, a { -webkit-tap-highlight-color: var(--clear); }
button { cursor: pointer; }
a { color: inherit; text-decoration: none; }
ul, ol { padding-inline-start: 1.5em; }
button, input, select, textarea { min-width: 0; }
fieldset { min-width: 0; border: 1px solid var(--border); border-radius: var(--r-inset); }
figure { margin: 0; }
h1, h2, h3 { font-family: var(--font-display); text-wrap: balance; overflow-wrap: break-word; }
h1 { margin: 0 0 24px; font-size: var(--fs-h1); font-weight: var(--weight-display); line-height: 1.14; letter-spacing: var(--tracking-cjk); }
h2 { margin: 0 0 24px; font-size: var(--fs-h2); font-weight: var(--weight-display); line-height: 1.25; letter-spacing: var(--tracking-cjk); }
h3 { margin: 0 0 16px; font-size: var(--fs-h3); font-weight: var(--weight-bold); line-height: 1.4; }
p { margin: 0 0 20px; }
strong { font-weight: var(--weight-strong); }
code, pre, kbd, samp { font-family: var(--font-mono); }
code { overflow-wrap: anywhere; }
pre {
  max-width: 100%;
  min-width: 0;
  overflow-x: auto;
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: var(--r-inset);
  background: var(--bg-panel);
  color: var(--text);
  font-size: var(--fs-ui);
  line-height: 1.7;
  tab-size: 2;
}
pre code { overflow-wrap: normal; word-break: normal; white-space: pre; }
:focus-visible { outline: var(--focus-width) solid var(--accent); outline-offset: var(--focus-offset); }
::selection { background: var(--accent-dark); color: var(--on-dark); }
.skip {
  position: absolute; left: 16px; top: 12px; z-index: 100;
  clip-path: inset(50%); width: 1px; height: 1px; overflow: hidden; white-space: nowrap;
  padding: 0; border-radius: var(--r-pill);
  background: var(--accent-dark); color: var(--on-dark); font-weight: var(--weight-semibold);
}
.skip:focus { clip-path: none; width: auto; height: auto; padding: 10px 18px; overflow: visible; white-space: normal; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0;
}
.shell { width: min(var(--frame), calc(100% - var(--gutter) * 2)); margin-inline: auto; }
.wrap {
  width: 100%; max-width: calc(var(--reading-frame) + var(--gutter) * 2);
  margin-inline: auto; padding-inline: var(--gutter);
}
.section { padding-top: var(--section-gap); padding-bottom: var(--section-gap); }
.section + .section { padding-top: 0; }
.stack > * + * { margin-top: 24px; }
.grid { display: grid; gap: 24px; }
.grid-two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-three { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid > *, .masthead-inner > *, .footer-grid > *, .tabs > * { min-width: 0; }
.nowrap { white-space: nowrap; }
.muted { color: var(--text-muted); }
.mono, .eyebrow { font-family: var(--font-mono); }
.eyebrow { display: block; margin-bottom: 16px; font-size: var(--fs-xs); letter-spacing: var(--tracking-mono); color: var(--text-muted); }
.text-link { color: var(--accent); text-decoration: underline; text-underline-offset: 4px; }
.lede { max-width: 700px; font-size: var(--fs-subtitle); color: var(--text-muted); line-height: 1.75; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 10px;
  min-height: 52px; max-width: 100%; padding: 12px 26px;
  border: 1.5px solid var(--clear); border-radius: var(--r-pill);
  font-size: var(--fs-body); font-weight: var(--weight-strong); line-height: 1.5;
  letter-spacing: var(--tracking-button); text-align: center;
  transition: background-color var(--ease), border-color var(--ease), color var(--ease);
}
.btn svg { width: 18px; height: 18px; flex-shrink: 0; }
.btn-primary { background: var(--accent-dark); color: var(--on-dark); }
.btn-primary:hover, .btn-primary.is-hover { background: var(--accent); color: var(--on-dark); }
.btn-outline { border-color: var(--text); background: var(--bg); color: var(--text); }
.btn-outline:hover, .btn-outline.is-hover { background: var(--bg-panel); color: var(--text); }
.btn-solid { background: var(--on-dark); color: var(--accent-dark); }
.btn-solid:hover { background: var(--bg-panel-2); color: var(--accent-dark); }
.btn-ghost { border-color: var(--on-dark-edge); background: var(--clear); color: var(--on-dark); }
.btn-ghost:hover { border-color: var(--on-dark); background: var(--on-dark-fill); color: var(--on-dark); }
.btn:active, .btn.is-active { border-color: var(--accent); }
.btn:disabled, .btn[aria-disabled="true"] { background: var(--bg-panel-2); color: var(--text-muted); border-color: var(--border); cursor: not-allowed; }
.btn.is-focus { outline: var(--focus-width) solid var(--accent); outline-offset: var(--focus-offset); }
.cta-row { display: flex; align-items: center; flex-wrap: wrap; gap: 14px; }
.card, .panel {
  border: 1px solid var(--border); background: var(--bg); color: var(--text);
  border-radius: var(--r-card); padding: 28px; min-width: 0;
}
.panel { border-radius: var(--r-plate); background: var(--bg-panel); color: var(--text); padding: 40px; }
.plate-dark { background: var(--text); color: var(--on-dark); border-color: var(--text); }
.plate-navy { background: var(--accent-dark); color: var(--on-dark); border-color: var(--accent-dark); }
.plate-dark .eyebrow, .plate-navy .eyebrow { color: var(--on-dark-soft); }
.decorated { position: relative; overflow-x: clip; }
.prose { min-width: 0; line-height: 1.9; }
.prose h2 { margin-top: 56px; scroll-margin-top: 28px; }
.prose h3 { margin-top: 32px; scroll-margin-top: 28px; }
.prose li + li { margin-top: 10px; }
.prose a { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }
.prose :not(pre) > code { padding: 2px 5px; background: var(--bg-panel); color: var(--accent-dark); border-radius: var(--r-field); font-size: .9em; }
.reveal { opacity: 1; transform: none; }
html.reveal-ready .reveal:not(.shown) { opacity: 0; transform: translateY(16px); }
html.reveal-ready .reveal { transition: opacity var(--reveal-time) ease, transform var(--reveal-time) ease; }
.reveal.shown { opacity: 1; transform: none; }

/* 页头使用独立宽版心，不复用阅读容器。 */
.masthead, #site-header { position: relative; z-index: 50; height: var(--nav-h); }
.masthead-inner {
  width: 100%; max-width: min(100%, calc(var(--header-frame) + var(--gutter) * 2));
  margin-inline: auto; padding-inline: var(--gutter); height: 100%;
  display: flex; align-items: center; gap: 24px;
}
.brand { display: inline-flex; align-items: center; gap: 12px; flex-shrink: 0; }
.brand-mark { width: 36px; height: 36px; flex-shrink: 0; }
.brand-name { font-size: var(--fs-brand); font-weight: var(--weight-display); letter-spacing: var(--tracking-brand); }
.primary-nav { margin-inline: auto; min-width: 0; }
.nav-list { display: flex; align-items: center; list-style: none; margin: 0; padding: 0; gap: 2px; }
.nav-link, .nav-more > summary {
  display: inline-flex; align-items: center; gap: 6px; min-height: 40px; padding: 0 16px;
  border-radius: var(--r-pill); font-size: var(--fs-nav); font-weight: var(--weight-medium);
  color: var(--text); cursor: pointer; white-space: nowrap; transition: background-color var(--ease);
}
.nav-link:hover, .nav-more > summary:hover { background: var(--bg-panel); color: var(--text); }
.nav-link[aria-current="page"] { color: var(--accent-dark); font-weight: var(--weight-strong); position: relative; }
.nav-link[aria-current="page"]::after {
  content: ""; position: absolute; left: 50%; bottom: 3px; width: 4px; height: 4px;
  margin-left: -2px; border-radius: var(--r-round); background: var(--accent);
}
.caret { width: 14px; height: 14px; flex-shrink: 0; transition: transform var(--ease); }
.nav-more, .lang { position: relative; }
.nav-more > summary, .lang > summary { list-style: none; }
.nav-more > summary::-webkit-details-marker, .lang > summary::-webkit-details-marker { display: none; }
details[open] > summary .caret { transform: rotate(180deg); }
.drop {
  position: absolute; top: calc(100% + 10px); min-width: 272px; padding: 10px;
  border: 1px solid var(--border); border-radius: var(--r-card);
  background: var(--bg); color: var(--text); z-index: 3;
}
.nav-more .drop { left: 50%; transform: translateX(-50%); }
.lang .drop { right: 0; min-width: 188px; }
.drop-label { display: block; padding: 6px 12px 8px; font-family: var(--font-mono); font-size: var(--fs-code); letter-spacing: var(--tracking-label); color: var(--text-muted); }
.drop-item { display: block; min-height: 44px; padding: 10px 12px; border-radius: var(--r-item); }
.drop-item:hover, .drop-item[aria-current="page"] { background: var(--bg-panel); color: var(--text); }
.drop-item b { display: block; font-size: var(--fs-nav-small); font-weight: var(--weight-semibold); }
.drop-item small { display: block; font-size: var(--fs-small); color: var(--text-muted); line-height: 1.5; white-space: normal; }
.tools { margin-left: auto; display: flex; align-items: center; gap: 12px; flex-shrink: 0; }
.lang > summary {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 44px;
  padding: 0 18px 0 16px; border: 1.5px solid var(--text); border-radius: var(--r-pill);
  font-size: var(--fs-nav); font-weight: var(--weight-ui); cursor: pointer;
}
.lang > summary:hover { background: var(--bg-panel); color: var(--text); }
.globe { width: 17px; height: 17px; flex-shrink: 0; }
.lang-short { display: none; }
.menu-toggle {
  display: none; align-items: center; justify-content: center; min-width: 44px; min-height: 44px;
  border: 1px solid var(--border); border-radius: var(--r-pill); background: var(--bg); color: var(--text);
}
.menu-toggle svg { width: 20px; height: 20px; }
.mobile-drawer { display: none; }
.menu-veil { position: fixed; inset: var(--nav-h) 0 0; z-index: 1; background: var(--veil); color: var(--on-dark); }
.static-mobile { display: none; }
.site-footer { margin-top: var(--section-gap); padding-top: 56px; padding-bottom: 28px; border-top: 1px solid var(--border); }
.footer-grid { display: grid; grid-template-columns: 1.2fr .8fr 1fr; gap: 48px; }
.footer-description { max-width: 350px; margin-top: 20px; color: var(--text-muted); font-size: var(--fs-nav); }
.footer-heading { margin: 0 0 16px; font-size: var(--fs-label); font-weight: var(--weight-bold); }
.footer-links { list-style: none; margin: 0; padding: 0; }
.footer-links a { display: inline-block; padding-top: 7px; padding-bottom: 7px; font-size: var(--fs-nav); color: var(--text-muted); }
.footer-links a:hover { color: var(--accent); text-decoration: underline; text-underline-offset: 4px; }
.footer-languages { display: flex; flex-wrap: wrap; gap: 12px 24px; margin-top: 40px; }
.footer-languages a { min-height: 44px; display: inline-flex; align-items: center; font-size: var(--fs-label); }
.footer-languages [aria-current="true"] { color: var(--accent); font-weight: var(--weight-semibold); }
.copyright { margin: 20px 0 0; padding-top: 24px; border-top: 1px solid var(--border); font-size: var(--fs-small); color: var(--text-muted); }
@media (max-width: 1040px) {
  .primary-nav { display: none; }
  .menu-toggle { display: inline-flex; }
  .tools { margin-left: auto; }
  .mobile-drawer:not([hidden]) {
    display: block; position: absolute; top: var(--nav-h); left: var(--gutter); right: var(--gutter);
    padding: 16px; border: 1px solid var(--border); border-radius: var(--r-card);
    background: var(--bg); color: var(--text); z-index: 2;
    max-height: calc(100dvh - var(--nav-h) - 16px); overflow-y: auto; overscroll-behavior: contain;
  }
  .mobile-drawer ul { list-style: none; padding: 0; margin: 0; }
  .mobile-drawer a { display: flex; width: 100%; align-items: center; min-height: 48px; padding: 12px 16px; border-radius: var(--r-inset); }
  .mobile-drawer a:hover, .mobile-drawer [aria-current="page"] { background: var(--bg-panel); color: var(--accent-dark); }
  .drawer-languages { margin-top: 16px; padding-top: 16px; border-top: 1px solid var(--border); }
  .static-mobile { display: block; position: relative; }
  .static-mobile .drop { right: 0; max-height: calc(100dvh - var(--nav-h) - 24px); overflow-y: auto; }
  .static-mobile .drop a { display: block; min-height: 44px; padding: 10px 12px; }
}
@media (max-width: 1040px) {
  :root { --gutter: 24px; --section-gap: 64px; }
}
@media (max-width: 768px) {
  h1 { font-size: var(--fs-mobile-h1); }
  .grid-three, .grid-two { grid-template-columns: minmax(0, 1fr); }
  .footer-grid { grid-template-columns: minmax(0, 1fr); gap: 28px; }
  .panel { padding: 24px; }
}
@media (max-width: 640px) {
  :root { --gutter: 16px; --section-gap: 48px; }
  .masthead-inner { gap: 12px; }
  .brand { gap: 8px; }
  .brand-name { font-size: var(--fs-body); }
  .brand-mark { width: 30px; height: 30px; }
  .tools { gap: 8px; margin-left: auto; }
  .lang > summary { padding-inline: 12px; gap: 6px; }
  .lang-full, .lang .globe { display: none; }
  .lang-short { display: inline; }
  .tilt, .rig { transform: none !important; }
  .card { padding: 22px; }
  pre { padding: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
  html.reveal-ready .reveal:not(.shown) { opacity: 1; transform: none; }
}