:root{
  --bg:#FAFAF9;
  --panel:#FFFFFF;
  --panel-2:#F0F0EE;
  --border:#E2E2DF;
  --accent:#1F6A9E;
  --accent-dark:#154D74;
  --skyline:#4FA9BF;
  --text:#16181B;
  --muted:#61656C;
  --faint:#8E9298;
  --ink:#16181B;
  --ink-hover:#2B2E33;
  --on-ink:#FFFFFF;
  --success:#2E8A57;
  --warn:#B5761C;
  --error:#C0392F;
  --sky-top:#DCE7EE;
  --sky-low:#F6F8F7;
  --earth-hi:#CAD8E2;
  --earth-lo:#A9BECC;
  --dot-gray:#CFD1CD;
  --flag-red:#C8423B;
  --flag-blue:#2E4A86;
  --flag-white:#FFFFFF;
  --glass:rgba(255,255,255,.78);
  --glass-edge:rgba(255,255,255,.92);
  --hair:rgba(22,24,27,.08);
  --hair-strong:rgba(22,24,27,.16);
  --shadow-tint:rgba(31,106,158,.10);
  --shadow-tint-2:rgba(31,106,158,.12);
  --shadow-near:rgba(31,106,158,.08);
  --shadow-btn:rgba(21,77,116,.22);
  --route:rgba(31,106,158,.4);
  --grat:rgba(21,77,116,.06);
  --label-halo:rgba(246,248,247,.82);
  --accent-ring:rgba(31,106,158,.16);
  --ok-ring:rgba(46,138,87,.16);
  --veil-strong:rgba(250,250,249,.93);
  --veil-mid:rgba(250,250,249,.82);
  --veil-0:rgba(250,250,249,0);
  --atmos-top:rgba(31,106,158,.03);
  --atmos-bottom:rgba(79,169,191,.06);
  --clear:transparent;
  --r-btn:2px;
  --r-card:4px;
  --r-round:50%;
  --font-display:'Inter','Noto Sans SC','PingFang SC','Hiragino Sans','Apple SD Gothic Neo','Microsoft YaHei',system-ui,sans-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','Noto Sans SC',ui-monospace,'SFMono-Regular',Menlo,Consolas,monospace;
  --weight-normal:400;
  --weight-title:500;
  --weight-brand:600;
  --text-base:16px;
  --text-small:14px;
  --text-micro:12px;
  --title-size:64px;
  --title-tracking:-.03em;
  --body-leading:1.625;
  --gutter:32px;
  --content-width:1440px;
  --reading-width:800px;
  --space-unit:8px;
  --section-space:96px;
  --anchor-offset:88px;
  --toc-offset:16px;
  --toc-landing:104px;
  --ease-time:.2s;
  --reveal-time:.6s;
  --panel-shadow:0 32px 80px var(--shadow-tint),0 2px 8px var(--shadow-near);
  --panel-highlight:inset 0 0 0 1px var(--glass-edge);
}
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:var(--anchor-offset)}
html,body{margin:0}
body{background:var(--bg);color:var(--text);font-family:var(--font-body);font-size:var(--text-base);line-height:var(--body-leading);-webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility}
html.nav-open{overflow:hidden}
img,video{display:block;max-width:100%;height:auto}
svg{flex-shrink:0}
button,input,select,textarea{font:inherit;color:inherit}
button{cursor:pointer}
a{color:inherit;text-underline-offset:3px}
:where(a,button,input,select,textarea,summary,[tabindex]):focus-visible{outline:2px solid var(--accent);outline-offset:3px}
[hidden]{display:none!important}
h1,h2,h3,h4{font-family:var(--font-display);font-weight:var(--weight-title);text-wrap:balance;overflow-wrap:break-word}
h1{font-size:clamp(52px,4.5vw,72px);line-height:1.12;letter-spacing:-.02em;margin:0 0 32px}
h2{font-size:clamp(28px,3vw,40px);line-height:1.2;letter-spacing:-.02em;margin:0 0 24px}
h3{font-size:24px;line-height:1.3;margin:0 0 16px}
p{margin:0 0 24px}
strong,b{font-weight:var(--weight-title)}
code{font-family:var(--font-mono);overflow-wrap:anywhere;background:var(--panel-2);padding:2px 4px;border-radius:var(--r-btn)}
pre{max-width:100%;overflow-x:auto;background:var(--panel-2);padding:24px;border-radius:var(--r-card)}
pre code{background:var(--clear);padding:0;white-space:pre;overflow-wrap:normal}
hr{border:0;border-top:1px solid var(--border);margin:32px 0}
.wrap,.shell{width:100%;max-width:var(--content-width);margin-inline:auto;padding-inline:var(--gutter)}
.reading-wrap{max-width:var(--reading-width);margin-inline:auto;min-width:0}
.section{padding-top:var(--section-space);padding-bottom:var(--section-space)}
:where(.grid,.three-up,.platform-grid,.footer-grid)>*{min-width:0}
.grid{display:grid;gap:32px}
.three-up{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:32px}
.stack>*+*{margin-top:24px}
.muted{color:var(--muted)}
.mono{font-family:var(--font-mono)}
.num{color:var(--accent);font-weight:var(--weight-title)}
.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.no-break{white-space:nowrap}
.sprite{position:absolute;width:0;height:0;overflow:hidden}
.panel,.card{background:var(--panel);border-radius:var(--r-card);box-shadow:var(--panel-highlight),var(--panel-shadow);min-width:0}
.panel{padding:40px}
.card{padding:32px}
.decorated-section{position:relative;overflow-x:clip}
.reveal{transition:opacity var(--reveal-time) ease,transform var(--reveal-time) ease}
.reveal.pending{opacity:0;transform:translateY(16px)}
.reveal.shown{opacity:1;transform:none}
#server-status{position:static;display:block;min-height:24px;max-width:100%;overflow:hidden;margin-top:24px;margin-bottom:24px}
#server-status+*{margin-top:24px}
.counter-stat{display:inline-block;min-width:3ch;font-variant-numeric:tabular-nums;font-family:var(--font-mono)}
.btn{--u:1px;display:inline-flex;align-items:center;justify-content:center;gap:calc(var(--u) * 8);height:calc(var(--u) * 48);padding:0 calc(var(--u) * 24);border:0;border-radius:var(--r-btn);font-size:calc(var(--u) * 16);font-weight:var(--weight-title);text-decoration:none;white-space:nowrap;flex-shrink:0;transition:background-color var(--ease-time) ease}
.btn svg{width:calc(var(--u) * 10);height:calc(var(--u) * 10)}
.btn-ink,.btn-primary{background:var(--ink);color:var(--on-ink);box-shadow:0 10px 28px var(--shadow-btn)}
.btn-ink:hover,.btn-primary:hover,.btn.is-hover{background:var(--ink-hover)}
.btn-gray,.btn-secondary{background:var(--panel-2);color:var(--text);box-shadow:inset 0 0 0 1px var(--border)}
.btn-gray:hover,.btn-secondary:hover{background:var(--panel)}
.btn:active,.btn.is-active{transform:translateY(1px)}
.btn:disabled,.btn[aria-disabled="true"]{background:var(--panel-2);color:var(--muted);box-shadow:none;cursor:not-allowed}
.btn.is-focus{outline:2px solid var(--accent);outline-offset:3px}
.button-row{display:flex;flex-wrap:wrap;gap:12px;align-items:center}
.chev{fill:none;stroke:currentColor;stroke-width:1.6;stroke-linecap:round;stroke-linejoin:round}
.first{background:linear-gradient(180deg,var(--atmos-top) 0%,var(--atmos-bottom) 100%);padding-bottom:32px;overflow-x:clip}
.topbar{min-height:40px;display:flex;align-items:center;justify-content:center;gap:16px;padding:0 16px;background:linear-gradient(90deg,var(--accent) 0%,var(--accent) 36%,var(--skyline) 100%);color:var(--on-ink);font-size:14px;font-weight:var(--weight-title);letter-spacing:.01em}
.topbar-text{white-space:nowrap}
.topbar-link{display:inline-flex;align-items:center;min-height:24px;color:inherit;text-decoration:underline;text-decoration-thickness:1px;text-underline-offset:3px;white-space:nowrap}
.topbar-btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;height:26px;padding:0 10px 0 12px;background:var(--panel);color:var(--text);border-radius:var(--r-btn);font-size:13px;font-weight:var(--weight-title);text-decoration:none;white-space:nowrap}
.topbar-btn svg{width:10px;height:10px}
#site-header{position:relative;z-index:30}
.nav{position:relative;height:64px;display:grid;grid-template-columns:auto 1fr auto;align-items:center;gap:32px}
.brand{display:inline-flex;align-items:center;gap:10px;text-decoration:none;color:var(--text)}
.brand img{width:28px;height:28px;flex-shrink:0}
.brand-en{font-family:var(--font-display);font-size:18px;font-weight:var(--weight-brand);letter-spacing:-.01em;white-space:nowrap}
.brand-zh{font-size:15px;font-weight:var(--weight-normal);color:var(--muted)}
.nav-list{display:flex;justify-content:center;align-items:center;list-style:none;margin:0;padding:0;font-size:15px}
.nav-list li{display:flex;align-items:center;white-space:nowrap}
.nav-list li+li::before{content:"·";color:var(--faint);margin:0 12px}
.nav-list a{position:relative;padding:6px 0;color:var(--text);text-decoration:none}
.nav-list a:hover{color:var(--accent-dark)}
.nav-list a[aria-current="page"]::after{content:"";position:absolute;left:0;right:0;bottom:0;height:1.5px;background:var(--ink)}
.nav-end{display:flex;align-items:center;gap:8px;justify-self:end}
.lang{display:inline-flex;align-items:center;justify-content:center;gap:6px;height:36px;min-width:44px;width:auto;padding:0 12px;border:0;background:var(--panel-2);color:var(--text);border-radius:var(--r-btn);font-size:14px;text-decoration:none;white-space:nowrap}
.lang svg{width:14px;height:14px;color:var(--muted)}
.lang span{white-space:nowrap}
.login{display:inline-flex;align-items:center;justify-content:center;height:36px;padding:0 18px;background:var(--ink);color:var(--on-ink);border-radius:var(--r-btn);font-size:14px;font-weight:var(--weight-title);text-decoration:none;white-space:nowrap}
.login:hover{background:var(--ink-hover)}
.language-picker{position:relative}
.language-menu{position:absolute;right:0;top:calc(100% + 8px);min-width:176px;padding:8px;background:var(--panel);box-shadow:var(--panel-shadow);border:1px solid var(--border);border-radius:var(--r-card);z-index:40}
.language-menu a{display:flex;align-items:center;min-height:44px;padding:8px 12px;text-decoration:none;white-space:nowrap}
.language-menu a:hover,.language-menu a[aria-current="true"]{background:var(--panel-2)}
.menu-toggle{display:none;align-items:center;justify-content:center;min-width:44px;min-height:44px;border:0;background:var(--panel-2);border-radius:var(--r-btn);font-size:22px}
.mobile-drawer{display:none}
.drawer-backdrop{display:none}
.site-footer{margin-top:64px;padding-top:64px;padding-bottom:32px;background:var(--panel-2);border-top:1px solid var(--border)}
.footer-grid{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:64px}
.footer-brand p{max-width:360px;margin-top:24px;color:var(--muted)}
.footer-title{font-size:16px;margin:0 0 16px;font-weight:var(--weight-title)}
.footer-links{list-style:none;padding:0;margin:0;display:grid;gap:8px}
.footer-links a{display:inline-flex;align-items:center;min-height:24px;text-decoration:none}
.footer-links a:hover{text-decoration:underline}
.footer-languages{display:flex;flex-wrap:wrap;gap:8px 24px;margin-top:40px}
.footer-languages a{display:inline-flex;align-items:center;min-height:32px}
.footer-bottom{display:flex;justify-content:space-between;flex-wrap:wrap;gap:16px;margin-top:32px;padding-top:24px;border-top:1px solid var(--border);font-size:14px;color:var(--muted)}
.legal-links{display:flex;flex-wrap:wrap;gap:16px}
.legal-links a{display:inline-flex;align-items:center;min-height:24px}
@media(max-width:1280px){
  .nav{gap:20px}
  .nav-list li+li::before{margin:0 8px}
}
@media(max-width:1100px){
  .desktop-nav{display:none}
  .nav{display:flex}
  .nav-end{margin-left:auto}
  .menu-toggle{display:inline-flex}
  .mobile-drawer:not([hidden]){display:block;position:absolute;top:100%;left:0;right:0;background:var(--panel);border-top:1px solid var(--border);padding:16px var(--gutter);max-height:calc(100dvh - 104px);overflow-y:auto;overscroll-behavior:contain;z-index:35}
  .mobile-drawer a{display:flex;width:100%;align-items:center;min-height:44px;padding:12px 16px;text-decoration:none;border-bottom:1px solid var(--border)}
  .mobile-drawer a[aria-current]{background:var(--panel-2)}
  .drawer-label{display:block;font-size:14px;color:var(--muted);padding:16px}
  .drawer-backdrop:not([hidden]){display:block;position:fixed;inset:104px 0 0;background:var(--hair-strong);border:0;z-index:29}
  .footer-grid{gap:32px}
}
@media(max-width:768px){
  :root{--gutter:16px;--section-space:56px;--anchor-offset:72px;--toc-landing:96px}
  h1{font-size:clamp(28px,7vw,40px);line-height:1.12}
  h2{font-size:28px}
  h3{font-size:22px}
  .nav{height:56px;gap:12px}
  .nav-end{margin-left:auto;gap:6px}
  .mobile-drawer:not([hidden]){max-height:calc(100dvh - 96px)}
  .drawer-backdrop:not([hidden]){top:96px}
  .three-up{grid-template-columns:minmax(0,1fr)}
  .panel,.card{padding:24px}
  .footer-grid{grid-template-columns:minmax(0,1fr)}
  .site-footer{padding-top:40px}
  .footer-bottom{display:block}
  .legal-links{margin-top:16px}
}
@media(max-width:640px){
  .no-break{white-space:normal}
  .tilt,[data-tilt]{transform:none!important}
  .decorated-section::before,.decorated-section::after,.stripe-halo{max-width:100%}
}
@media(max-width:480px){
  .topbar{font-size:13px;gap:12px}
  .topbar-text{min-width:0;white-space:normal}
  .topbar-btn{flex-shrink:0}
  .topbar-link{display:none}
  .brand-zh{display:none}
  .lang{padding-inline:8px}
  .login{padding-inline:12px}
}
@media(max-width:360px){
  .topbar{font-size:11px;gap:8px}
  .topbar-btn{font-size:12px;padding-inline:8px}
  .brand{gap:6px}
  .brand-en{font-size:16px}
  .nav{gap:8px}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .reveal,.reveal.pending,.reveal.shown{opacity:1;transform:none;transition:none}
  .btn{transition:none}
}