:root{
  --bg:#E8EDF6;--bg-top:#EFF3FA;--bg-bottom:#E2E8F3;--bg-panel:#F7F9FD;--bg-panel-2:#DCE3EF;--bg-chrome:#EEF2F9;--white:#FFFFFF;
  --border:#C9D2E2;--border-soft:#D6DDEA;--accent:#D9485A;--accent-dark:#B0344A;--text:#18202F;--text-muted:#586379;--text-faint:#7D879C;--success:#2A9A6A;--warn:#C2860F;--error:#C23A30;--cobalt:#4E6BD6;
  --ink:#18202F;--device:#1E2638;--wall-a:#2B3956;--wall-b:#3E4F78;--on-dark:#F7F9FD;--on-dark-muted:rgba(247,249,253,.62);--on-dark-line:rgba(247,249,253,.38);--on-accent:#FFFFFF;--on-accent-muted:rgba(255,255,255,.88);
  --hl:rgba(255,255,255,.95);--hl-dark:rgba(255,255,255,.14);--hl-accent:rgba(255,255,255,.26);--hl-tube:rgba(255,255,255,.2);--hex-line:rgba(255,255,255,.055);--grid-line:rgba(78,107,214,.12);
  --coral-10:rgba(217,72,90,.10);--coral-12:rgba(217,72,90,.12);--coral-24:rgba(217,72,90,.24);--coral-35:rgba(217,72,90,.35);--ink-06:rgba(24,32,47,.06);--ink-12:rgba(24,32,47,.12);--shade-deep:rgba(10,14,26,.42);--success-16:rgba(42,154,106,.16);--clear:transparent;
  --flag-red:#D8263A;--flag-white:#FFFFFF;--flag-navy:#1D2B6B;--flag-blue:#2B3F8C;--flag-black:#1B1B1F;--flag-gold:#F2C12E;--flag-edge:rgba(24,32,47,.16);
  --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","Malgun Gothic","Microsoft YaHei",system-ui,sans-serif;
  --font-mono:"JetBrains Mono",ui-monospace,"SFMono-Regular",Menlo,Consolas,monospace;
  --weight-normal:400;--weight-medium:500;--weight-semibold:600;--weight-bold:700;
  --size-xs:12px;--size-sm:14px;--size-body:16px;--size-lead:20px;--size-h1:64px;--size-h2:36px;--size-h3:24px;--size-mobile-h1:36px;
  --r-xs:4px;--r-sm:6px;--r-md:8px;--r-screen:9px;--r-dev:16px;--r-float:24px;--r-pill:999px;--r-round:50%;
  --gutter:24px;--content-width:1200px;--header-height:56px;--anchor-offset:80px;--toc-offset:76px;--toc-landing:148px;
  --shadow-card:inset 0 1px 0 var(--hl),0 1px 2px var(--ink-06),0 22px 48px -16px var(--coral-10);
  --shadow-lead:inset 0 1px 0 var(--hl-accent),0 22px 44px -16px var(--coral-35);
  --shadow-float:inset 0 1px 0 var(--hl),0 2px 6px var(--ink-06),0 28px 56px -18px var(--coral-24);
  --shadow-device:inset 0 1px 0 var(--hl-dark),0 -8px 64px -12px var(--coral-12),0 40px 90px -24px var(--coral-12);
  --ease:cubic-bezier(.2,.7,.2,1);--duration:.2s;
}
*,*::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:var(--weight-normal) var(--size-body)/1.75 var(--font-body);-webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility}
img{max-width:100%;height:auto;vertical-align:middle}
svg{vertical-align:middle;flex-shrink:0}
button,input,select,textarea{font:inherit;color:inherit}
button{cursor:pointer}
a{color:inherit;text-underline-offset:4px}
:where(a,button,input,select,textarea,summary,[tabindex]):focus-visible{outline:2px solid var(--cobalt);outline-offset:3px;border-radius:var(--r-xs)}
button:disabled,[aria-disabled="true"]{cursor:not-allowed;opacity:.6}
[hidden]{display:none!important}
h1,h2,h3,h4{font-family:var(--font-display);font-weight:var(--weight-bold);line-height:1.25;text-wrap:balance}
h1{font-size:clamp(52px,5vw,var(--size-h1));letter-spacing:-.02em}
h2{font-size:var(--size-h2);letter-spacing:-.02em}
h3{font-size:var(--size-h3)}
p{margin:0 0 1em}
h1,h2,h3{margin:0 0 .6em}
ul,ol{padding-left:1.5em}
code{font-family:var(--font-mono);overflow-wrap:anywhere;font-size:.9em}
pre{max-width:100%;overflow-x:auto;padding:20px;background:var(--bg-panel-2);border:1px solid var(--border);border-radius:var(--r-sm)}
pre code{overflow-wrap:normal;white-space:pre}
table{border-collapse:collapse}
th,td{word-break:keep-all}
.wrap{width:100%;max-width:calc(var(--content-width) + 2 * var(--gutter));margin-inline:auto;padding-inline:var(--gutter);min-width:0}
.section{padding-top:72px;padding-bottom:72px}
.reading-wrap{max-width:860px;margin-inline:auto;min-width:0}
.prose{min-width:0;overflow-wrap:break-word}
.prose h2{margin-top:1.8em}
.prose h3{margin-top:1.4em}
.prose p,.prose li{line-height:1.9}
.no-break{white-space:nowrap}
.muted{color:var(--text-muted)}
.kicker{font:var(--weight-medium) var(--size-xs)/1.4 var(--font-mono);letter-spacing:.14em;text-transform:uppercase;color:var(--text-muted)}
.panel{padding:28px;background:var(--bg-panel);border:1px solid var(--border-soft);border-radius:var(--r-md);box-shadow:var(--shadow-card);min-width:0}
.grid{display:grid;gap:24px}
.grid>*{min-width:0}
.grid-three{grid-template-columns:repeat(3,minmax(0,1fr))}
.grid-five{grid-template-columns:repeat(5,minmax(0,1fr))}
.btn,.btn-primary,.btn-secondary,.btn-login{display:inline-flex;align-items:center;justify-content:center;gap:10px;min-height:44px;padding:0 22px;border-radius:var(--r-sm);font:var(--weight-semibold) var(--size-body)/1.3 var(--font-body);text-decoration:none;white-space:nowrap;flex-shrink:0;transition:background var(--duration),color var(--duration),transform var(--duration);border:1px solid var(--ink)}
.btn,.btn-primary{background:var(--ink);color:var(--on-dark);box-shadow:inset 0 1px 0 var(--hl-dark),0 12px 26px -12px var(--ink-12)}
.btn-primary svg{width:14px;height:14px}
.btn-primary:hover,.btn.is-hover{transform:translateY(-1px)}
.btn-secondary{background:var(--bg-panel);color:var(--text)}
.btn-secondary:hover,.btn-login:hover{background:var(--ink);color:var(--on-dark)}
.btn.is-focus{outline:2px solid var(--cobalt);outline-offset:3px}
.btn-text{display:inline-flex;align-items:center;min-height:24px;font:var(--weight-medium) var(--size-body)/1.4 var(--font-body);text-decoration:underline;text-underline-offset:6px;text-decoration-thickness:1.5px}
.btn-text:hover{color:var(--text-muted)}
.reveal{transition:opacity .6s var(--ease),transform .6s var(--ease)}
.reveal.pending{opacity:0;transform:translateY(16px)}
.reveal.shown{opacity:1;transform:none}
#server-status{position:relative;display:block;min-width:0;max-width:100%;overflow:hidden;margin-block:24px}
#server-status+*{margin-top:32px}
#site-header{position:relative;z-index:40}
.annbar{height:40px;background:var(--ink);color:var(--on-dark)}
.annbar .wrap{height:100%;display:flex;align-items:center;justify-content:space-between;gap:24px}
.ann-msg{display:flex;align-items:center;gap:12px;margin:0;font:var(--weight-medium) var(--size-xs)/1 var(--font-mono);letter-spacing:.14em;text-transform:uppercase}
.ann-msg svg{width:14px;height:15px}
.ann-tag{color:var(--on-dark-muted)}
.ann-sep{width:1px;height:12px;background:var(--on-dark-line);flex:none}
.ann-link{display:inline-flex;align-items:center;min-height:24px;font:var(--weight-medium) var(--size-xs)/1.4 var(--font-mono);letter-spacing:.12em;text-decoration:underline;text-underline-offset:5px;text-decoration-color:var(--on-dark-line)}
.ann-link:hover{text-decoration-color:var(--on-dark)}
.nav{height:var(--header-height);background:var(--bg-panel);border-bottom:1px solid var(--border-soft);position:relative;z-index:42}
.nav .wrap{height:100%;display:flex;align-items:center;gap:40px}
.brand{display:inline-flex;align-items:center;gap:10px;text-decoration:none;font:var(--weight-bold) 19px/1 var(--font-display);letter-spacing:-.01em;flex-shrink:0;min-height:34px}
.brand img{width:24px;height:26px;object-fit:contain}
.brand-zh{font-weight:var(--weight-medium);color:var(--text-muted)}
.tabs{display:flex;align-items:center;list-style:none;margin:0;padding:0;height:100%;gap:2px}
.tabs li{height:100%;display:flex}
.tab{position:relative;display:flex;align-items:center;padding:0 14px;font-size:14.5px;color:var(--text-muted);text-decoration:none;white-space:nowrap}
.tab::after{content:"";position:absolute;left:14px;right:14px;bottom:-1px;height:2px;border-radius:var(--r-xs);background:var(--ink);transform:scaleX(0);transition:transform var(--duration)}
.tab:hover{color:var(--text)}
.tab:hover::after{transform:scaleX(.35)}
.tab.is-active{color:var(--text);font-weight:var(--weight-semibold)}
.tab.is-active::after{transform:scaleX(1)}
.desktop-nav{height:100%;min-width:0}
.nav-right{margin-left:auto;display:flex;align-items:center;gap:20px;flex-shrink:0}
.lang-picker{position:relative}
.lang{display:inline-flex;align-items:center;justify-content:center;gap:6px;min-height:34px;min-width:44px;width:auto;padding:4px 0;border:0;background:var(--clear);font:var(--weight-normal) var(--size-sm)/1 var(--font-body);color:var(--text-muted)}
.lang span{white-space:nowrap}
.lang-menu{position:absolute;right:0;top:calc(100% + 8px);width:176px;padding:6px;background:var(--bg-panel);border:1px solid var(--border);border-radius:var(--r-md);box-shadow:var(--shadow-float)}
.lang-menu a{display:flex;align-items:center;min-height:44px;padding:8px 12px;text-decoration:none;border-radius:var(--r-xs)}
.lang-menu a:hover,.lang-menu a[aria-current]{background:var(--bg-panel-2)}
.btn-login{min-height:34px;padding:0 18px;font-size:var(--size-sm);background:var(--bg-panel);color:var(--text)}
.menu-toggle{display:none;min-width:44px;min-height:44px;padding:8px;border:1px solid var(--border);border-radius:var(--r-sm);background:var(--bg-panel);font-size:var(--size-lead)}
.mobile-nav{display:none}
html.nav-open{overflow:hidden}
.nav-veil{position:fixed;inset:0;z-index:41;background:var(--shade-deep);border:0}
.site-footer{background:var(--bg-panel-2);border-top:1px solid var(--border);padding-top:56px;padding-bottom:24px}
.footer-grid{display:grid;grid-template-columns:2fr 1.3fr 1.5fr 1fr;gap:40px}
.footer-grid>*{min-width:0}
.footer-brand p{margin-top:20px;max-width:320px;color:var(--text-muted)}
.footer-title{font-size:var(--size-sm);font-weight:var(--weight-semibold);margin:0 0 12px}
.footer-links{list-style:none;padding:0;margin:0;display:grid;gap:4px}
.footer-links a{display:inline-flex;align-items:center;min-height:28px;font-size:var(--size-sm);text-decoration:none}
.footer-links a:hover{text-decoration:underline}
.footer-bottom{display:flex;justify-content:space-between;align-items:center;gap:20px;flex-wrap:wrap;margin-top:40px;padding-top:20px;border-top:1px solid var(--border);color:var(--text-muted);font-size:var(--size-xs)}
.footer-legal{display:flex;flex-wrap:wrap;gap:16px}
.footer-legal a{display:inline-flex;align-items:center;min-height:24px}
@media(max-width:1100px){
  .nav .wrap{gap:20px}.tab{padding-inline:10px}.tab::after{left:10px;right:10px}.nav-right{gap:12px}
}
@media(max-width:900px){
  .desktop-nav{display:none}.nav-right{margin-left:auto;gap:8px}.menu-toggle{display:inline-flex;align-items:center;justify-content:center}
  .mobile-nav{position:absolute;top:100%;left:0;right:0;z-index:44;background:var(--bg-panel);border-bottom:1px solid var(--border);max-height:calc(100dvh - 96px);overflow-y:auto;overscroll-behavior:contain;padding:12px var(--gutter) 20px}
  .mobile-nav:not([hidden]){display:block}.mobile-nav a{display:flex;align-items:center;width:100%;min-height:44px;padding:10px 14px;text-decoration:none;border-radius:var(--r-xs)}
  .mobile-nav a.is-active,.mobile-nav a[aria-current]{background:var(--bg-panel-2);font-weight:var(--weight-semibold)}
  .mobile-language-list{border-top:1px solid var(--border);margin-top:12px;padding-top:12px}
  .annbar{height:auto}.annbar .wrap{flex-wrap:wrap;gap:8px 16px;padding-block:10px}.ann-msg{flex-wrap:wrap;line-height:1.4}
  .footer-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.grid-five{grid-template-columns:repeat(2,minmax(0,1fr))}
}
@media(max-width:768px){
  h1{font-size:var(--size-mobile-h1);line-height:1.22}h2{font-size:28px}.section{padding-top:48px;padding-bottom:48px}
  .grid-three{grid-template-columns:1fr}
}
@media(max-width:640px){
  :root{--gutter:16px}
  .no-break{white-space:normal}.tilt{transform:none!important}
  .decorative-layer,[data-hero-visual]{max-width:100%}
  .footer-grid{grid-template-columns:1fr;gap:28px}.nav .wrap{gap:8px}
  .lang-picker{display:none}.brand{font-size:17px}.btn-login{padding-inline:12px}
  .panel{padding:20px}
}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .reveal,.reveal.pending{opacity:1;transform:none;transition:none}
  *,*::before,*::after{animation:none!important;transition:none!important}
}