:root{
  --bg:#E4EDF2;--hero-top:#EEF4F7;--hero-bottom:#DCE7EE;--panel:#F6F9FB;--panel-2:#D5E2E9;--card:#FFFFFF;--border:#C3D3DC;--line-soft:#E1E9EE;
  --accent:#1C5650;--accent-2:#2D7469;--accent-dark:#123B37;--teal-gray:#6E9598;--text:#15262B;--muted:#546A72;--success:#2F8A5B;--warn:#C98A2B;--error:#C2453B;--info:#4A7F9C;
  --apricot:#F6E2CB;--apricot-line:#E4BB8C;--ice:#C9E3EA;--mint:#D4EDE1;--sky-1:#D6E5EE;--sky-2:#BCD2DF;--sage-1:#DDE7E6;--sage-2:#C2D5D3;--on-accent:#F6F9FB;
  --flag-red:#C8393B;--flag-blue:#2C3F70;--flag-green:#2E7D50;--flag-white:#FFFFFF;--flag-ring:rgba(21,38,43,.16);
  --accent-a06:rgba(28,86,80,.06);--accent-a08:rgba(28,86,80,.08);--accent-a10:rgba(28,86,80,.10);--accent-a12:rgba(28,86,80,.12);--accent-a28:rgba(28,86,80,.28);--deep-a30:rgba(18,59,55,.30);--success-a14:rgba(47,138,91,.14);
  --white-a0:rgba(255,255,255,0);--white-a06:rgba(255,255,255,.06);--white-a10:rgba(255,255,255,.10);--white-a14:rgba(255,255,255,.14);--white-a22:rgba(255,255,255,.22);--white-a50:rgba(255,255,255,.50);--white-a72:rgba(255,255,255,.72);--white-a90:rgba(255,255,255,.90);
  --halo-apricot:rgba(246,226,203,.92);--halo-apricot-0:rgba(246,226,203,0);--halo-ice:rgba(184,222,231,.80);--halo-ice-0:rgba(184,222,231,0);--nav-bg:rgba(238,244,247,.84);--card-edge:rgba(195,211,220,.55);--veil-bg:rgba(21,38,43,.30);
  --lift:0 18px 48px var(--accent-a12),0 2px 6px var(--accent-a08);--edge-hi:inset 0 0 0 1px var(--white-a50),inset 0 1px 0 var(--white-a90);
  --r-card:12px;--r-tag:10px;--r-sm:8px;--r-tiny:3px;--r-chrome:9px;--r-cap:6px;--r-pill:999px;--r-circle:50%;
  --font-display:'Songti SC','STSong','Noto Serif CJK SC','Source Han Serif SC','Noto Serif SC',Georgia,'Times New Roman',serif;
  --font-body:'Inter','Noto Sans SC','PingFang SC','Hiragino Sans','Apple SD Gothic Neo','Microsoft YaHei',system-ui,sans-serif;
  --font-mono:'JetBrains Mono',ui-monospace,'SFMono-Regular',Menlo,Consolas,monospace;
  --gutter:24px;--wrap-width:1228px;--header-height:72px;--anchor-space:88px;--toc-offset:144px;
  --size-body:16px;--size-h1:clamp(52px,4.65vw,68px);--size-h2:44px;--size-h3:24px;--weight-display:400;--weight-medium:500;--weight-strong:600;
  --ease-ui:cubic-bezier(.2,.7,.2,1);--time-ui:.2s;--time-reveal:.65s;
}
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-padding-top:var(--anchor-space);scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font-family:var(--font-body);font-size:var(--size-body);line-height:1.6;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}
html.nav-open{overflow:hidden}
a{color:inherit;text-decoration:none}
button,input,select,textarea{font:inherit;color:inherit}
button{background:none;border:0;padding:0;cursor:pointer}
button:disabled{cursor:not-allowed}
img{max-width:100%;height:auto}
svg{flex-shrink:0}
ul{list-style:none;margin:0;padding:0}
p{margin:0}
h1,h2,h3{font-family:var(--font-display);font-weight:var(--weight-display);letter-spacing:-.02em;line-height:1.15;text-wrap:balance}
h1{font-size:var(--size-h1)}
h2{font-size:var(--size-h2)}
h3{font-size:var(--size-h3)}
[hidden]{display:none!important}
:focus-visible{outline:2px solid var(--accent);outline-offset:3px;border-radius:var(--r-sm)}
::selection{background:var(--panel-2);color:var(--text)}
.wrap{width:100%;max-width:var(--wrap-width);margin-inline:auto;padding-inline:var(--gutter)}
.section{padding-top:72px;padding-bottom:72px}
.grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:24px}
.grid>*,.wrap>*,.prose,.panel,.card{min-width:0}
.panel,.card{border-radius:var(--r-card);background:var(--panel);box-shadow:var(--edge-hi),var(--lift);padding:28px}
.card{background:var(--card)}
.muted{color:var(--muted)}
.eyebrow{font-size:13px;letter-spacing:.06em;color:var(--muted)}
.no-break{white-space:nowrap}
.sprite{position:absolute;width:0;height:0;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}
.prose{max-width:820px;overflow-wrap:break-word}
.prose p,.prose ul,.prose ol,.prose pre{margin-block:20px}
.prose ul{list-style:disc;padding-left:24px}
.prose ol{padding-left:24px}
.prose a{text-decoration:underline;text-underline-offset:4px}
.prose h2{margin-top:48px}
.prose h3{margin-top:32px}
code{font-family:var(--font-mono);overflow-wrap:anywhere;background:var(--panel-2);border-radius:var(--r-tiny);padding:2px 5px}
pre{max-width:100%;overflow-x:auto;background:var(--panel-2);border-radius:var(--r-card);padding:20px}
pre code{padding:0;background:inherit;white-space:pre;overflow-wrap:normal}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:10px;min-height:52px;padding:0 30px;border-radius:var(--r-pill);font-size:16px;font-weight:var(--weight-medium);letter-spacing:.02em;flex-shrink:0;white-space:nowrap;max-width:100%;transition:transform var(--time-ui),background-color var(--time-ui),color var(--time-ui),box-shadow var(--time-ui)}
.btn-outline,.btn-secondary{border:1.5px solid var(--text);color:var(--text)}
.btn-outline:hover,.btn-secondary:hover{background:var(--text);color:var(--on-accent)}
.btn-solid,.btn-primary{background:linear-gradient(180deg,var(--accent-2),var(--accent));color:var(--on-accent);padding:0 26px 0 32px;box-shadow:inset 0 1px 0 var(--white-a22),0 12px 28px var(--accent-a28)}
.btn-solid:hover,.btn-primary:hover{transform:translateY(-1px);box-shadow:inset 0 1px 0 var(--white-a22),0 16px 34px var(--accent-a28)}
.btn:active{transform:translateY(1px)}
.btn:disabled,.btn[aria-disabled="true"]{background:var(--panel-2);color:var(--muted);box-shadow:none;border-color:var(--border);transform:none;pointer-events:none}
.btn-small{min-height:44px;padding-inline:20px;font-size:14px}
.cta-row{margin-top:28px;display:flex;justify-content:center;gap:16px;flex-wrap:wrap}
.topbar,#site-header{position:sticky;top:0;z-index:40}
.topbar{background:var(--nav-bg);-webkit-backdrop-filter:blur(14px);backdrop-filter:blur(14px);border-bottom:1px solid var(--card-edge)}
.topbar-in{width:min(1376px,calc(100% - 48px));margin:auto;height:var(--header-height);display:flex;align-items:center;gap:28px}
.brand{display:inline-flex;align-items:center;gap:10px;flex-shrink:0;min-height:44px}
.brand img{width:36px;height:36px}
.brand-en{font-weight:650;font-size:17px;letter-spacing:.04em;color:var(--text)}
.brand-zh{font-size:13px;font-weight:var(--weight-display);color:var(--muted)}
.mainnav{min-width:0}
.mainnav ul{display:flex;align-items:center;list-style:none;margin:0;padding:0;gap:2px}
.mainnav a{display:block;padding:7px 13px;border-radius:var(--r-pill);font-size:14.5px;color:var(--muted);white-space:nowrap;transition:color var(--time-ui),background-color var(--time-ui)}
.mainnav a:hover{color:var(--text);background:var(--white-a50)}
.mainnav a[aria-current="page"]{background:var(--panel-2);color:var(--text);font-weight:var(--weight-medium);box-shadow:inset 0 1px 0 var(--white-a72)}
.bar-end{margin-left:auto;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:44px;width:auto;font-size:14px;color:var(--muted);padding:7px 6px;white-space:nowrap}
.lang span{white-space:nowrap}
.lang-menu{position:absolute;right:0;top:100%;min-width:180px;padding:8px;background:var(--panel);border:1px solid var(--border);border-radius:var(--r-card);box-shadow:var(--lift)}
.lang-menu a{display:flex;align-items:center;min-height:44px;padding:8px 12px;border-radius:var(--r-sm)}
.lang-menu a:hover,.lang-menu a[aria-current="true"]{background:var(--panel-2)}
.login{display:inline-flex;align-items:center;justify-content:center;min-height:40px;padding:0 22px;border-radius:var(--r-pill);border:1.5px solid var(--text);font-size:14.5px;font-weight:var(--weight-medium);color:var(--text);white-space:nowrap;transition:background-color var(--time-ui),color var(--time-ui)}
.login:hover{background:var(--text);color:var(--on-accent)}
.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-sm)}
.menu-toggle svg{width:20px;height:20px}
.mobile-nav{display:none}
.nav-veil{position:fixed;inset:var(--header-height) 0 0;background:var(--veil-bg);z-index:-1}
.site-footer{background:var(--panel-2);border-top:1px solid var(--border);padding-top:64px;padding-bottom:28px}
.footer-grid{display:grid;grid-template-columns:1.25fr 1fr 1fr;gap:48px}
.footer-grid>*{min-width:0}
.footer-brand p{margin-top:20px;max-width:340px;color:var(--muted)}
.footer-heading{font-family:var(--font-body);font-weight:var(--weight-strong);font-size:15px;margin:0 0 16px}
.footer-links{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:4px 16px}
.footer-links a,.footer-languages a,.footer-legal a{display:inline-flex;align-items:center;min-height:32px;font-size:14px}
.footer-links a:hover,.footer-languages a:hover,.footer-legal a:hover{text-decoration:underline;text-underline-offset:4px}
.footer-languages{display:flex;gap:8px 24px;flex-wrap:wrap;margin-top:36px}
.footer-bottom{display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap;margin-top:28px;padding-top:24px;border-top:1px solid var(--border);font-size:13px;color:var(--muted)}
.footer-legal{display:flex;gap:20px}
.help-bubble{position:fixed;right:24px;bottom:calc(24px + env(safe-area-inset-bottom,0px));z-index:60;width:56px;height:56px;border-radius:var(--r-circle);display:grid;place-items:center;background:linear-gradient(160deg,var(--accent-2),var(--accent) 70%);color:var(--on-accent);box-shadow:inset 0 1px 0 var(--white-a22),0 14px 32px var(--accent-a28);transition:transform var(--time-ui)}
.help-bubble svg{width:26px;height:26px}
.help-bubble:hover{transform:translateY(-2px)}
body:has(.help-bubble)::after{content:"";display:block;height:calc(88px + env(safe-area-inset-bottom,0px))}
.reveal{transition:opacity var(--time-reveal) var(--ease-ui),transform var(--time-reveal) var(--ease-ui)}
.reveal.pending{opacity:0;transform:translateY(16px)}
.reveal.shown{opacity:1;transform:none}
#server-status{position:relative;display:block;min-height:80px;width:100%;max-width:100%;overflow:hidden;margin-block:24px}
#server-status+*{margin-top:24px}
#server-status>*{min-width:0;max-width:100%}
body:has(.toc-tabs) section[id]{scroll-margin-top:var(--toc-offset)}
@media(max-width:1240px){
  .mainnav{display:none}
  .topbar-in{gap:16px}
  .bar-end{margin-left:auto}
  .menu-toggle{display:inline-flex}
  .mobile-nav:not([hidden]){display:block;position:absolute;left:0;right:0;top:100%;z-index:2;background:var(--panel);padding:16px var(--gutter) 24px;max-height:calc(100dvh - var(--header-height));overflow-y:auto;overscroll-behavior:contain;box-shadow:var(--lift)}
  .mobile-nav a{display:flex;align-items:center;width:100%;min-height:44px;padding:10px 16px;border-radius:var(--r-pill)}
  .mobile-nav a[aria-current="page"],.mobile-nav a:hover{background:var(--panel-2)}
  .mobile-language-list{border-top:1px solid var(--border);margin-top:12px;padding-top:12px}
}
@media(max-width:768px){
  h1{font-size:36px;line-height:1.2}
  h2{font-size:32px}
  .grid,.footer-grid{grid-template-columns:1fr}
  .footer-grid{gap:32px}
  .section{padding-top:48px;padding-bottom:48px}
  .brand-zh{display:none}
  .btn{min-height:48px;padding-inline:24px}
  .help-bubble{right:16px;bottom:calc(16px + env(safe-area-inset-bottom,0px))}
}
@media(max-width:640px){
  :root{--gutter:16px}
  .hero{overflow-x:clip}
  .no-break{white-space:normal}
  .tilt{transform:none!important}
  .topbar-in{width:calc(100% - 32px);gap:8px}
  .bar-end{gap:6px;margin-left:auto}
  .brand{gap:6px}
  .brand img{width:30px;height:30px}
  .brand-en{font-size:15px}
  .login{padding-inline:14px}
  .lang{font-size:12px;padding-inline:4px}
  .panel,.card{padding:20px}
  .footer-links{gap:6px 12px}
  .decorated{overflow-x:clip;max-width:100%}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .reveal,.reveal.pending,.reveal.shown{opacity:1;transform:none;transition:none}
  *,*::before,*::after{animation:none!important;transition:none!important}
}