:root {
  --bg:#FAFBFC;
  --panel:#FFFFFF;
  --panel-2:#F2F4F8;
  --border:#E3E6EE;
  --border-strong:#CDD2DE;
  --accent:#4361EE;
  --accent-dark:#2E46C4;
  --leaf:#67B66E;
  --forest:#1C5A35;
  --text:#14161F;
  --muted:#5A6072;
  --faint:#8A90A2;
  --success:#3E9F57;
  --warn:#C98A12;
  --error:#D23F3F;
  --announce:#ECEFFD;
  --accent-wash:rgba(67,97,238,.055);
  --accent-tint:rgba(67,97,238,.09);
  --accent-shadow:rgba(67,97,238,.12);
  --accent-shadow-s:rgba(67,97,238,.09);
  --leaf-glow:rgba(103,182,110,.20);
  --leaf-soft:#E2F1E3;
  --leaf-line:#67B66E;
  --success-ring:rgba(62,159,87,.18);
  --slot:#ECEEF2;
  --grid-line:rgba(67,97,238,.075);
  --line:#EDEFF4;
  --seam:rgba(67,97,238,.07);
  --chrome-low:#F8F9FC;
  --hl:#FFFFFF;
  --mark-hl:rgba(255,255,255,.35);
  --btn-hl:rgba(255,255,255,.14);
  --btn-solid-hover:#2A2D3A;
  --ink-shadow:rgba(20,22,31,.05);
  --dot-ring:rgba(20,22,31,.10);
  --veil:rgba(20,22,31,.30);
  --flag-red:#D7263D;
  --flag-white:#FFFFFF;
  --flag-blue:#1F3A8A;
  --flag-ring:rgba(20,22,31,.14);
  --clear:transparent;

  --r-xs:6px;
  --r-s:8px;
  --r-m:12px;
  --r-l:20px;
  --r-pill:999px;
  --r-round:50%;
  --r-flag:4px;
  --r-flag-sm:3px;
  --r-slot:7px;
  --r-bubble:12px 12px 4px 12px;
  --r-rule:2px;

  --f-display:"Inter","Noto Sans SC","PingFang SC","Hiragino Sans","Microsoft YaHei",system-ui,sans-serif;
  --f-body:"Inter","Noto Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,-apple-system,sans-serif;
  --f-mono:"JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  --fs-body:16px;
  --fs-small:14px;
  --fs-caption:12px;
  --fs-display:66px;
  --fs-h2:36px;
  --fs-h3:22px;
  --weight-regular:400;
  --weight-medium:500;
  --weight-semibold:600;
  --space-1:8px;
  --space-2:16px;
  --space-3:24px;
  --space-4:32px;
  --space-5:40px;
  --space-6:48px;
  --space-8:64px;
  --space-9:72px;
  --space-12:96px;
  --gutter:40px;
  --wrap-max:1280px;
  --reading-max:840px;
  --header-row:64px;
  --notice-height:40px;
  --header-edge:104px;
  --anchor-offset:120px;
  --toc-offset:80px;
  --toc-landing:152px;
  --shadow-card:0 12px 32px var(--accent-shadow-s),inset 0 1px 0 var(--hl);
  --shadow-window:0 24px 60px var(--accent-shadow),0 2px 6px var(--ink-shadow),inset 0 1px 0 var(--hl);
  --ease:cubic-bezier(.2,.7,.2,1);
  --fast:150ms;
  --reveal-duration:350ms;
}
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-padding-top:var(--anchor-offset);scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font-family:var(--f-body);font-size:var(--fs-body);line-height:1.6;-webkit-font-smoothing:antialiased}
[hidden]{display:none!important}
a{color:inherit;text-underline-offset:4px}
button,input,select,textarea{font:inherit}
button{color:inherit;cursor:pointer}
button,select,input,textarea{max-width:100%}
button{border:0}
img{display:block;max-width:100%;height:auto}
svg{display:block;flex-shrink:0}
svg:not([width]){width:24px;height:24px}
ul,ol{padding-inline-start:24px}
li::marker{color:var(--muted)}
hr{border:0;border-top:1px solid var(--border);margin-block:var(--space-4)}
::selection{background:var(--leaf-soft);color:var(--text)}
:where(a,button,input,select,textarea,summary,[tabindex]):focus-visible{outline:2px solid var(--accent);outline-offset:3px}
:where(main,section,article,nav,div,aside)>*{min-width:0}
.wrap{width:100%;max-width:var(--wrap-max);padding-inline:var(--gutter);margin-inline:auto}
.reading-wrap{width:100%;max-width:var(--reading-max);padding-inline:var(--gutter);margin-inline:auto}
.section{padding-top:var(--space-9);padding-bottom:var(--space-9)}
.section-tight{padding-top:var(--space-6);padding-bottom:var(--space-6)}
.section-head{max-width:760px;margin:0 auto var(--space-5);text-align:center}
.section-head p{color:var(--muted)}
h1,h2,h3,h4{font-family:var(--f-display);font-weight:var(--weight-regular);text-wrap:balance;overflow-wrap:break-word}
h1{margin:0 0 16px;font-size:var(--fs-display);line-height:1.1;letter-spacing:-.02em}
h2{margin:0 0 24px;font-size:var(--fs-h2);line-height:1.25;letter-spacing:-.02em}
h3{margin:0 0 16px;font-size:var(--fs-h3);line-height:1.4}
h4{margin:0 0 12px;font-size:var(--fs-body);font-weight:var(--weight-medium)}
p{margin:0 0 20px}
strong,b{font-weight:var(--weight-semibold)}
small{font-size:var(--fs-caption)}
.no-break{white-space:nowrap}
.muted{color:var(--muted)}
.mono{font-family:var(--f-mono);font-variant-numeric:tabular-nums}
.grad{background:linear-gradient(90deg,var(--accent) 6%,var(--leaf) 94%);-webkit-background-clip:text;background-clip:text;color:var(--clear);-webkit-text-fill-color:var(--clear)}
code{font-family:var(--f-mono);font-size:.9em;overflow-wrap:anywhere;background:var(--panel-2);border-radius:var(--r-xs);padding:2px 5px}
pre{max-width:100%;overflow-x:auto;padding:var(--space-3);background:var(--panel-2);border:1px solid var(--border);border-radius:var(--r-s);font-family:var(--f-mono);font-size:var(--fs-small)}
pre code{padding:0;background:var(--clear);white-space:pre;overflow-wrap:normal}
.prose{overflow-wrap:break-word}
.prose h2{margin-top:var(--space-8)}
.prose h3{margin-top:var(--space-4)}
.prose p,.prose li{line-height:1.85}
.prose li+li{margin-top:var(--space-1)}
.prose a:where(:not(.btn)){color:var(--accent-dark)}
.panel,.card{background:var(--panel);border:1px solid var(--border);border-radius:var(--r-m);box-shadow:var(--shadow-card);padding:var(--space-4);min-width:0}
.inset-panel{background:var(--panel-2);border:1px solid var(--border);border-radius:var(--r-s);padding:var(--space-3)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:48px;padding:10px 30px;border:1px solid var(--clear);border-radius:var(--r-pill);font-size:var(--fs-body);font-weight:var(--weight-medium);line-height:1.5;text-decoration:none;white-space:nowrap;flex-shrink:0;transition:transform var(--fast),background var(--fast),box-shadow var(--fast)}
.btn:hover{transform:translateY(-1px)}
.btn-solid,.btn-primary{background:var(--text);color:var(--panel);box-shadow:0 10px 24px var(--accent-shadow),inset 0 1px 0 var(--btn-hl)}
.btn-solid:hover,.btn-primary:hover{background:var(--btn-solid-hover)}
.btn-line,.btn-secondary{background:var(--panel);border-color:var(--text);color:var(--text)}
.btn-line:hover,.btn-secondary:hover{background:var(--panel-2)}
.btn:active{transform:translateY(0)}
.btn:disabled,.btn[aria-disabled="true"]{cursor:not-allowed;background:var(--panel-2);color:var(--muted);border-color:var(--border);box-shadow:none;transform:none}
.btn-small{min-height:40px;padding:8px 20px;font-size:var(--fs-small)}
.icon-button{display:inline-flex;align-items:center;justify-content:center;min-width:44px;min-height:44px;padding:8px;background:var(--panel);border:1px solid var(--border);border-radius:var(--r-s)}
.sprite{position:absolute;width:0!important;height:0!important;overflow:hidden}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap;border:0}

/* Shared header. The bar has no transformed or filtered ancestor. */
#site-header{position:relative;z-index:50}
.notice{background:var(--announce);font-size:var(--fs-small);color:var(--text)}
.notice a{display:flex;align-items:center;justify-content:center;gap:8px;min-height:var(--notice-height);padding-inline:16px;text-decoration:none}
.notice strong{font-weight:var(--weight-semibold)}
.notice .sep{color:var(--muted)}
.notice .arr{font-weight:var(--weight-semibold)}
.topbar{position:relative;z-index:53;background:var(--panel);border-bottom:1px solid var(--border)}
.header-row{display:flex;align-items:center;min-height:var(--header-row);gap:28px;flex-wrap:nowrap}
.brand{display:inline-flex;align-items:center;gap:10px;text-decoration:none;flex-shrink:0;min-height:40px}
.brand-logo{width:30px;height:30px;border-radius:var(--r-s);flex-shrink:0}
.brand-en{font-family:var(--f-display);font-size:17px;font-weight:var(--weight-semibold);letter-spacing:-.01em;white-space:nowrap}
.brand-zh{font-size:var(--fs-small);font-weight:var(--weight-regular);color:var(--muted);white-space:nowrap}
.desktop-nav{display:flex;align-items:center;align-self:stretch;flex:1;min-width:0;gap:2px}
.tabs{display:flex;align-items:center;justify-content:center;list-style:none;margin:0;padding:0;gap:2px;min-height:var(--header-row);flex:1;min-width:0}
.nav-more{position:relative;flex-shrink:0}
.nav-more-toggle{display:flex;align-items:center;min-height:var(--header-row);padding:0 8px;font-size:var(--fs-small);color:var(--muted);background:var(--clear);cursor:pointer;white-space:nowrap}
.nav-more-toggle::after{content:'⌄';margin-left:6px}
.nav-more-panel{position:absolute;right:0;top:100%;z-index:60;min-width:220px;max-width:calc(100vw - 32px);padding:8px;margin:0;list-style:none;background:var(--panel);border:1px solid var(--border);border-radius:var(--r-s);box-shadow:var(--shadow-card)}
.nav-more-panel a{display:flex;align-items:center;min-height:44px;padding:8px 12px;font-size:var(--fs-small);text-decoration:none;overflow-wrap:anywhere;border-radius:var(--r-xs)}
.nav-more-panel a:hover,.nav-more-panel a[aria-current="page"]{background:var(--announce);color:var(--accent-dark)}
.tabs li{align-self:stretch;display:flex;flex-shrink:0}
.tabs a{position:relative;display:flex;align-items:center;min-height:var(--header-row);padding:0 12px;font-size:var(--fs-small);color:var(--muted);text-decoration:none;white-space:nowrap}
.tabs a:hover{color:var(--text)}
.tabs a[aria-current="page"]{color:var(--text);font-weight:var(--weight-medium)}
.tabs a[aria-current="page"]::after{content:"";position:absolute;left:12px;right:12px;bottom:0;height:2px;border-radius:var(--r-rule);background:var(--accent)}
.tools{display:flex;align-items:center;gap:14px;flex-shrink:0}
.lang-picker{position:relative}
.lang{display:inline-flex;align-items:center;justify-content:center;gap:6px;min-width:44px;min-height:36px;width:auto;padding:4px 0;border:0;background:var(--clear);font-size:var(--fs-small);color:var(--muted);white-space:nowrap}
.lang-text{white-space:nowrap}
.lang:hover{color:var(--text)}
.lang-panel{position:absolute;right:0;top:calc(100% + 12px);z-index:60;min-width:180px;padding:8px;background:var(--panel);border:1px solid var(--border);border-radius:var(--r-s);box-shadow:var(--shadow-card)}
.lang-panel a{display:flex;align-items:center;min-height:44px;padding:8px 12px;text-decoration:none;border-radius:var(--r-xs);font-size:var(--fs-small);white-space:nowrap}
.lang-panel a:hover,.lang-panel a[aria-current="true"]{background:var(--announce);color:var(--accent-dark)}
.login{display:inline-flex;align-items:center;justify-content:center;min-height:36px;padding:6px 18px;border:1px solid var(--text);border-radius:var(--r-pill);background:var(--panel);font-size:var(--fs-small);font-weight:var(--weight-medium);text-decoration:none;white-space:nowrap}
.login:hover{background:var(--text);color:var(--panel)}
.menu-toggle{display:none;align-items:center;justify-content:center;min-width:44px;min-height:44px;background:var(--clear);border:1px solid var(--border);border-radius:var(--r-s)}
.menu-glyph{display:flex;flex-direction:column;gap:4px;align-items:center}
.menu-line{display:block;width:20px;height:2px;background:currentColor;border-radius:var(--r-rule)}
.menu-toggle[aria-expanded="true"]{background:var(--announce);color:var(--accent-dark)}
.mobile-drawer{position:fixed;z-index:52;top:var(--header-edge);right:0;left:0;height:calc(100dvh - var(--header-edge));max-height:calc(100dvh - var(--header-edge));overflow-y:auto;overscroll-behavior:contain;padding:16px var(--gutter) 32px;background:var(--panel);border-top:1px solid var(--border)}
.mobile-drawer ul{list-style:none;margin:0;padding:0}
.mobile-drawer a{display:flex;align-items:center;width:100%;min-height:44px;padding:12px 16px;text-decoration:none;border-radius:var(--r-s)}
.mobile-drawer a:hover,.mobile-drawer a[aria-current="page"],.mobile-drawer a[aria-current="true"]{background:var(--announce);color:var(--accent-dark)}
.drawer-languages{margin-top:16px;padding-top:16px;border-top:1px solid var(--border)}
.nav-veil{position:fixed;z-index:51;inset:var(--header-edge) 0 0;background:var(--veil)}
html.nav-open{overflow:hidden}

/* Footer */
.site-footer{background:var(--panel-2);border-top:1px solid var(--border);padding-top:56px;padding-bottom:24px}
.footer-grid{display:grid;grid-template-columns:1.5fr 1fr 1fr;gap:48px}
.footer-brand p{max-width:360px;margin-top:20px;font-size:var(--fs-small);color:var(--muted)}
.footer-title{font-size:var(--fs-small);font-weight:var(--weight-medium);margin-bottom:16px}
.footer-links{list-style:none;margin:0;padding:0;display:grid;gap:6px;grid-template-columns:repeat(2,minmax(0,1fr))}
.footer-links a,.footer-languages a,.footer-legal a{display:inline-flex;align-items:center;min-height:28px;font-size:var(--fs-small);text-decoration:none;color:var(--muted)}
.footer-links a:hover,.footer-languages a:hover,.footer-legal a:hover{color:var(--accent-dark);text-decoration:underline}
.footer-languages{display:flex;flex-wrap:wrap;gap:8px 20px;margin-top:40px;padding-top:24px;border-top:1px solid var(--border)}
.footer-languages a[aria-current="true"]{color:var(--text);font-weight:var(--weight-medium)}
.footer-bottom{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:12px 24px;margin-top:24px;color:var(--muted);font-size:var(--fs-caption)}
.footer-bottom p{margin:0}
.footer-legal{display:flex;flex-wrap:wrap;gap:16px}
.footer-legal a{font-size:var(--fs-caption)}

/* Progressive enhancement: the document is visible without scripts. */
.reveal{transition:opacity var(--reveal-duration) var(--ease),transform var(--reveal-duration) var(--ease)}
.reveal.pending{opacity:0;transform:translateY(16px)}
.reveal.shown{opacity:1;transform:none}
.decor-region{position:relative;overflow-x:clip;max-width:100%}
.decor-layer{position:absolute;inset:0;pointer-events:none;max-width:100%}
#server-status{position:relative;display:block;min-height:160px;width:100%;max-width:100%;overflow:hidden;margin-block:24px}
#server-status+*{margin-top:32px}
#server-status :where(.grid,.server-grid){min-width:0;max-width:100%}

@media(min-width:1025px){
  .mobile-drawer,.nav-veil{display:none!important}
  html.nav-open{overflow:auto}
}
@media(max-width:1180px){
  .header-row{gap:18px}
  .tabs a{padding-inline:8px}
  .tabs a[aria-current="page"]::after{left:8px;right:8px}
}
@media(max-width:1024px){
  .desktop-nav{display:none}
  .tools{margin-left:auto}
  .menu-toggle{display:inline-flex}
  .header-row{gap:16px}
  h1{font-size:56px}
  .footer-grid{grid-template-columns:1.2fr 1fr;gap:32px}
  .footer-brand{grid-column:1/-1}
}
@media(max-width:768px){
  :root{--gutter:16px;--fs-h2:28px;--fs-h3:20px}
  h1{font-size:36px;line-height:1.18}
  .section{padding-top:56px;padding-bottom:56px}
  .section-tight{padding-top:32px;padding-bottom:32px}
  .panel,.card{padding:24px}
  .footer-grid{grid-template-columns:1fr 1fr;gap:24px}
}
@media(max-width:640px){
  :root{--notice-height:48px;--header-edge:112px}
  .no-break{white-space:normal}
  .notice{font-size:13px}
  .notice a{flex-wrap:wrap;align-content:center;gap:0 6px;padding-block:4px;line-height:20px}
  .tools{gap:6px;margin-left:auto}
  .header-row{gap:8px}
  .lang-text{display:none}
  .lang{padding-inline:4px}
  .brand-en{font-size:15px}
  .brand-logo{width:26px;height:26px}
  .brand{gap:6px}
  .login{padding-inline:12px;font-size:13px}
  .tilt,.decor-tilt{transform:none}
  .decor-layer{max-width:100%}
  .footer-grid{grid-template-columns:1fr}
  .footer-brand{grid-column:auto}
  .btn{padding-inline:24px}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation:none!important;transition:none!important}
  .reveal,.reveal.pending,.reveal.shown{opacity:1;transform:none}
}