:root{
  --ink-900:#08131F;
  --ink-800:#0E1F31;
  --ink-700:#16304A;
  --line:#2A4763;
  --steel:#7C96B2;
  --mist:#D6E0EA;
  --paper:#F3F6F9;
  --amber:#F0B33C;
  --amber-soft:#F8D98F;
  --cinnabar:#E2503B;
  --cinnabar-bright:#FF7259;
  --signal:#57C08A;
  --focus:#6FA8FF;
  --grid:24px;
  --wrap:1180px;
  --shadow-soft:0 18px 44px rgba(0,0,0,.38);
  --sans:"Noto Sans SC","Source Han Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --heading:"Noto Sans SC","Source Han Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --mono:"JetBrains Mono","IBM Plex Mono","SFMono-Regular",ui-monospace,monospace;
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,p,figure,blockquote,dl,dd{margin:0}
ul,ol{margin:0;padding:0;list-style:none}
img,svg{max-width:100%}
button{font:inherit;color:inherit}
a{color:inherit}

body{
  min-height:100vh;
  background-color:var(--ink-900);
  background-image:
    radial-gradient(120% 62% at 50% -12%, rgba(22,48,74,.9) 0%, rgba(8,19,31,0) 64%),
    linear-gradient(to right, rgba(42,71,99,.26) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(42,71,99,.26) 1px, transparent 1px);
  background-size:auto, var(--grid) var(--grid), var(--grid) var(--grid);
  background-attachment:fixed, fixed, fixed;
  color:var(--mist);
  font-family:var(--sans);
  font-size:16px;
  font-weight:400;
  line-height:1.85;
  letter-spacing:.005em;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}

::selection{background:var(--amber);color:var(--ink-900)}

h1,h2,h3,h4{
  font-family:var(--heading);
  color:var(--paper);
  font-weight:800;
  line-height:1.3;
  letter-spacing:-.02em;
}

:focus-visible{outline:3px solid var(--focus);outline-offset:2px}
a:focus-visible,button:focus-visible{outline:3px solid var(--focus);outline-offset:3px}

#main-content{scroll-margin-top:104px}

.wrap{
  width:100%;
  max-width:var(--wrap);
  margin-inline:auto;
  padding-inline:clamp(18px,4vw,40px);
}

.mono{
  font-family:var(--mono);
  font-variant-ligatures:none;
  letter-spacing:.06em;
}

.sr-only{
  position:absolute;
  width:1px;height:1px;
  margin:-1px;padding:0;
  overflow:hidden;
  clip:rect(0 0 0 0);
  clip-path:inset(50%);
  white-space:nowrap;
  border:0;
}

.skip-link{
  position:fixed;
  top:10px;left:10px;
  z-index:300;
  transform:translateY(-160%);
  background:var(--amber);
  color:var(--ink-900);
  font-family:var(--mono);
  font-size:12px;
  letter-spacing:.1em;
  text-decoration:none;
  padding:10px 16px;
  border:1px solid var(--amber);
  transition:transform .16s ease-out;
}
.skip-link:focus,
.skip-link:focus-visible{transform:translateY(0)}

/* ============ header ============ */
.site-header{
  position:sticky;
  top:0;
  z-index:60;
  background:rgba(8,19,31,.95);
  border-bottom:1px solid var(--line);
  backdrop-filter:blur(8px);
}

.toprail{
  border-bottom:1px solid rgba(42,71,99,.72);
  background:linear-gradient(90deg, rgba(22,48,74,.42), rgba(8,19,31,0) 60%);
  transition:border-color .18s ease-out,background-color .18s ease-out;
}
.toprail__inner{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:14px;
  min-height:40px;
}
.toprail__index{
  font-size:11px;
  letter-spacing:.2em;
  color:var(--steel);
  white-space:nowrap;
}
.toprail__index b{color:var(--amber);font-weight:500}

.version-switch{
  display:inline-flex;
  border:1px solid var(--line);
  background:rgba(14,31,49,.9);
}
.version-switch__btn{
  appearance:none;
  border:0;
  border-right:1px solid var(--line);
  background:transparent;
  color:var(--steel);
  font-family:var(--mono);
  font-size:11px;
  line-height:1.2;
  letter-spacing:.06em;
  padding:8px 12px;
  cursor:pointer;
  transition:color .16s ease-out,background-color .16s ease-out;
}
.version-switch__btn:last-child{border-right:0}
.version-switch__btn:hover{color:var(--paper);background:rgba(42,71,99,.55)}
.version-switch__btn[aria-pressed="true"]{background:var(--amber);color:var(--ink-900)}
.site-header[data-version="v3"] .toprail{
  border-bottom-color:rgba(226,80,59,.5);
  background:linear-gradient(90deg, rgba(226,80,59,.14), rgba(8,19,31,0) 62%);
}
.site-header[data-version="v3"] .toprail__index b{color:var(--cinnabar-bright)}
.site-header[data-version="v3"] .version-switch__btn[aria-pressed="true"]{background:var(--cinnabar);color:var(--paper)}
.site-header[data-version="v3"] .brand__mark{color:var(--cinnabar-bright);border-color:rgba(226,80,59,.55)}

.masthead{padding-block:clamp(12px,2.2vw,22px);transition:padding .18s ease-out}
.masthead__inner{
  display:grid;
  grid-template-columns:minmax(0,1fr) auto minmax(0,1fr);
  align-items:center;
  gap:clamp(12px,3vw,34px);
}
.masthead__note{
  margin:0;
  max-width:26ch;
  font-size:11px;
  line-height:1.7;
  letter-spacing:.13em;
  color:var(--steel);
  transition:opacity .18s ease-out;
}

.brand{
  display:grid;
  justify-items:center;
  gap:5px;
  padding:2px 6px;
  text-align:center;
  text-decoration:none;
}
.brand__mark{
  font-family:var(--mono);
  font-size:10.5px;
  line-height:1.4;
  letter-spacing:.34em;
  padding:2px 8px 2px 11px;
  color:var(--amber);
  border:1px solid rgba(240,179,60,.5);
  transition:color .16s ease-out,border-color .16s ease-out;
}
.brand__name{
  font-family:var(--heading);
  font-weight:900;
  font-size:clamp(25px,3.4vw,38px);
  line-height:1.06;
  letter-spacing:-.02em;
  color:var(--paper);
  transition:color .16s ease-out,font-size .18s ease-out;
}
.brand__sub{
  font-family:var(--mono);
  font-size:10px;
  line-height:1.5;
  letter-spacing:.26em;
  color:var(--steel);
  transition:opacity .18s ease-out;
}
.brand:hover .brand__name{color:var(--amber-soft)}
.brand:hover .brand__mark{color:var(--amber-soft);border-color:var(--amber-soft)}

.masthead__actions{
  display:flex;
  align-items:center;
  justify-content:flex-end;
  gap:10px;
}
.quick-action{
  display:inline-flex;
  align-items:center;
  gap:8px;
  text-decoration:none;
  font-family:var(--mono);
  font-size:12px;
  letter-spacing:.1em;
  padding:9px 14px;
  color:var(--ink-900);
  background:var(--amber);
  border:1px solid var(--amber);
  transition:background-color .16s ease-out,border-color .16s ease-out;
}
.quick-action::after{content:"→";font-size:13px;line-height:1}
.quick-action:hover{background:var(--amber-soft);border-color:var(--amber-soft)}

.nav-toggle{
  display:none;
  align-items:center;
  gap:9px;
  padding:9px 12px;
  background:transparent;
  border:1px solid var(--line);
  color:var(--paper);
  font-family:var(--mono);
  font-size:11px;
  letter-spacing:.14em;
  cursor:pointer;
  transition:border-color .16s ease-out,color .16s ease-out;
}
.nav-toggle:hover{border-color:var(--amber);color:var(--amber-soft)}
.nav-toggle__label{line-height:1.2}
.nav-toggle__bars{display:grid;gap:4px;width:16px}
.nav-toggle__bars span{
  display:block;
  height:1px;
  background:currentColor;
  transition:transform .18s ease-out;
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:first-child{transform:translateY(2.5px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:last-child{transform:translateY(-2.5px) rotate(-45deg)}

.site-nav{
  display:block;
  border-top:1px solid var(--line);
  background:linear-gradient(180deg, rgba(14,31,49,.72), rgba(8,19,31,0));
}
.nav-list{
  display:flex;
  flex-wrap:wrap;
  align-items:stretch;
  justify-content:center;
}
.nav-list__item{border-left:1px solid rgba(42,71,99,.6)}
.nav-list__item:first-child{border-left:0}
.nav-link{
  position:relative;
  display:inline-flex;
  align-items:baseline;
  gap:8px;
  padding:13px clamp(9px,1.5vw,19px);
  font-size:14.5px;
  font-weight:500;
  letter-spacing:.01em;
  color:var(--mist);
  text-decoration:none;
  transition:color .16s ease-out,background-color .16s ease-out;
}
.nav-link__num{
  font-family:var(--mono);
  font-size:10.5px;
  letter-spacing:.04em;
  color:var(--steel);
  transition:color .16s ease-out;
}
.nav-link:hover{color:var(--amber-soft);background:rgba(42,71,99,.36)}
.nav-link:hover .nav-link__num{color:var(--amber)}
.nav-link[aria-current="page"]{color:var(--amber)}
.nav-link[aria-current="page"] .nav-link__num{color:var(--amber)}
.nav-link[aria-current="page"]::after{
  content:"";
  position:absolute;
  left:8px;right:8px;bottom:-1px;
  height:2px;
  background:var(--amber);
}

.nav-list__case{
  margin-left:clamp(6px,1.4vw,18px);
  border-left:2px solid var(--amber);
}
.nav-case{
  display:inline-flex;
  align-items:baseline;
  gap:9px;
  padding:13px clamp(11px,1.8vw,22px);
  font-size:14.5px;
  font-weight:600;
  color:var(--paper);
  text-decoration:none;
  background:rgba(240,179,60,.08);
  transition:background-color .16s ease-out,color .16s ease-out;
}
.nav-case__num{
  font-family:var(--mono);
  font-size:10px;
  letter-spacing:.18em;
  color:var(--amber);
}
.nav-case:hover{background:rgba(240,179,60,.18);color:var(--amber-soft)}

.site-header[data-stuck="true"] .masthead{padding-block:9px}
.site-header[data-stuck="true"] .masthead__note{opacity:0}
.site-header[data-stuck="true"] .brand__sub{opacity:.45}
.site-header[data-stuck="true"] .brand__name{font-size:clamp(22px,2.4vw,26px)}

.scroll-meter{height:2px;background:rgba(42,71,99,.55);overflow:hidden}
.scroll-meter__bar{
  display:block;
  height:100%;
  width:100%;
  transform:scaleX(0);
  transform-origin:left center;
  background:linear-gradient(90deg,var(--cinnabar),var(--amber));
  transition:transform .1s linear;
}

/* ============ footer ============ */
.site-footer{
  position:relative;
  z-index:1;
  margin-top:clamp(48px,7vw,96px);
  background:var(--ink-800);
  border-top:1px solid var(--line);
  color:var(--mist);
}
.footer-rail{
  height:12px;
  background-color:var(--ink-900);
  background-image:repeating-linear-gradient(90deg, rgba(240,179,60,.45) 0 1px, transparent 1px 24px);
  border-bottom:1px solid var(--line);
}
.footer-inner{
  display:grid;
  gap:clamp(26px,4vw,50px);
  padding-block:clamp(34px,5vw,62px) clamp(20px,3vw,30px);
}
.footer-lead{display:grid;gap:14px;max-width:56ch}
.footer-tagline{
  font-family:var(--heading);
  font-size:clamp(23px,3.2vw,33px);
  font-weight:800;
  line-height:1.32;
  letter-spacing:-.02em;
  color:var(--paper);
}
.footer-guide{
  font-size:14.5px;
  line-height:1.85;
  color:var(--steel);
  max-width:46ch;
}
.footer-lead__cta{justify-self:start}

.footer-cols{
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  gap:clamp(20px,3vw,40px);
  padding-top:clamp(22px,3vw,34px);
  border-top:1px solid rgba(42,71,99,.85);
}
.footer-col{min-width:0}
.footer-col__title{
  margin:0 0 12px;
  font-family:var(--mono);
  font-size:11px;
  font-weight:500;
  letter-spacing:.22em;
  color:var(--amber);
}
.footer-col__list{display:grid;gap:9px}
.footer-link{
  display:inline-block;
  font-size:14.5px;
  line-height:1.7;
  color:var(--mist);
  text-decoration:none;
  border-bottom:1px solid transparent;
  transition:color .16s ease-out,border-color .16s ease-out;
}
.footer-link:hover{color:var(--amber-soft);border-bottom-color:rgba(240,179,60,.6)}

.footer-col--contact{min-width:0}
.footer-contact{
  display:grid;
  gap:11px;
  font-style:normal;
}
.footer-contact__row{display:grid;gap:3px;min-width:0}
.footer-contact__label{
  font-family:var(--mono);
  font-size:10.5px;
  letter-spacing:.18em;
  color:var(--steel);
}
.copy-btn{
  display:inline-flex;
  align-items:center;
  gap:10px;
  justify-self:start;
  max-width:100%;
  padding:6px 10px;
  background:transparent;
  border:1px solid var(--line);
  color:var(--paper);
  font-family:var(--mono);
  font-size:12px;
  letter-spacing:.03em;
  text-align:left;
  cursor:pointer;
  transition:border-color .16s ease-out,color .16s ease-out,background-color .16s ease-out;
}
.copy-btn__text{min-width:0;overflow-wrap:anywhere;line-height:1.5}
.copy-btn__hint{
  flex:none;
  font-size:9.5px;
  letter-spacing:.18em;
  color:var(--steel);
  transition:color .16s ease-out;
}
.copy-btn:hover{border-color:var(--amber);color:var(--amber-soft);background:rgba(240,179,60,.08)}
.copy-btn[data-copied="true"]{border-color:rgba(87,192,138,.75)}
.copy-btn[data-copied="true"] .copy-btn__hint{color:var(--signal)}
.footer-address{
  font-size:14px;
  line-height:1.8;
  color:var(--steel);
}

.footer-base{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:10px 24px;
  padding-top:18px;
  border-top:1px solid rgba(42,71,99,.85);
}
.footer-legal{
  font-family:var(--mono);
  font-size:11.5px;
  letter-spacing:.08em;
  color:var(--steel);
}

/* ============ shared components ============ */
.section{padding-block:clamp(34px,5.5vw,72px)}
.section > .wrap{display:block}

.page-title{
  font-family:var(--heading);
  font-weight:900;
  font-size:clamp(29px,4.6vw,50px);
  line-height:1.14;
  letter-spacing:-.02em;
  color:var(--paper);
  margin:0 0 14px;
}

.section-label{
  display:flex;
  align-items:center;
  gap:10px;
  margin:0 0 14px;
  font-family:var(--mono);
  font-size:11px;
  letter-spacing:.22em;
  color:var(--steel);
}
.section-label::after{
  content:"";
  flex:1 1 auto;
  height:1px;
  background:var(--line);
}

.breadcrumbs{
  margin:0 0 18px;
  font-family:var(--mono);
  font-size:11.5px;
  letter-spacing:.06em;
  color:var(--steel);
}
.breadcrumbs ol{display:flex;flex-wrap:wrap;align-items:center;gap:8px}
.breadcrumbs li{display:inline-flex;align-items:center;gap:8px}
.breadcrumbs li + li::before{content:"/";color:var(--line)}
.breadcrumbs a{color:var(--steel);text-decoration:none}
.breadcrumbs a:hover{color:var(--amber-soft)}
.breadcrumbs [aria-current="page"]{color:var(--mist)}

.grid{display:grid;gap:clamp(16px,2.4vw,28px)}
.grid--2{grid-template-columns:repeat(2,minmax(0,1fr))}
.grid--3{grid-template-columns:repeat(3,minmax(0,1fr))}
.grid--aside{
  grid-template-columns:260px minmax(0,1fr);
  align-items:start;
  gap:clamp(22px,4vw,54px);
}

.panel{
  position:relative;
  padding:clamp(18px,2.6vw,28px);
  background:var(--ink-700);
  border:1px solid var(--line);
  transition:transform .16s ease-out,border-color .16s ease-out;
}
.panel:hover{transform:translateY(-2px);border-color:var(--amber)}

.frame{
  position:relative;
  padding:clamp(20px,3vw,38px);
  border:1px solid var(--line);
  background:linear-gradient(180deg, rgba(22,48,74,.55), rgba(8,19,31,.18));
}
.frame::before{
  content:"";
  position:absolute;
  inset:8px;
  border:1px solid rgba(42,71,99,.55);
  pointer-events:none;
}

.tag{
  display:inline-flex;
  align-items:center;
  gap:6px;
  padding:3px 7px;
  font-family:var(--mono);
  font-size:11px;
  line-height:1.5;
  letter-spacing:.06em;
  color:var(--steel);
  background:rgba(22,48,74,.6);
  border:1px solid var(--line);
  text-decoration:none;
  transition:color .16s ease-out,border-color .16s ease-out,background-color .16s ease-out;
}
.tag:hover{color:var(--paper);border-color:var(--steel)}
.tag--current{color:var(--amber);border-color:rgba(240,179,60,.7);background:rgba(240,179,60,.1)}
.tag--legacy{color:var(--cinnabar-bright);border-color:rgba(226,80,59,.7);background:rgba(226,80,59,.1)}
.tag--ok{color:var(--signal);border-color:rgba(87,192,138,.6);background:rgba(87,192,138,.08)}

.btn{
  display:inline-flex;
  align-items:center;
  gap:8px;
  padding:11px 18px;
  font-family:var(--mono);
  font-size:12.5px;
  line-height:1.4;
  letter-spacing:.08em;
  text-decoration:none;
  color:var(--paper);
  background:transparent;
  border:1px solid var(--line);
  cursor:pointer;
  transition:color .16s ease-out,border-color .16s ease-out,background-color .16s ease-out;
}
.btn--primary{background:var(--amber);border-color:var(--amber);color:var(--ink-900)}
.btn--primary:hover{background:var(--amber-soft);border-color:var(--amber-soft)}
.btn--ghost:hover{border-color:var(--amber);color:var(--amber-soft);background:rgba(240,179,60,.08)}

.prose{
  max-width:38em;
  font-size:16.5px;
  line-height:1.85;
  color:var(--mist);
}
.prose p{margin:0 0 1.05em}
.prose p:last-child{margin-bottom:0}
.prose h2{margin:1.5em 0 .55em;font-size:26px;line-height:1.34}
.prose h3{margin:1.3em 0 .45em;font-size:19px;line-height:1.4;font-weight:700}
.prose strong{color:var(--paper);font-weight:700}
.prose a{color:var(--amber);text-decoration:none;border-bottom:1px solid rgba(240,179,60,.5)}
.prose a:hover{color:var(--amber-soft);border-bottom-color:var(--amber-soft)}
.prose ul{list-style:disc;padding-left:1.3em;margin:0 0 1.05em}
.prose ol{list-style:decimal;padding-left:1.4em;margin:0 0 1.05em}
.prose li{margin-bottom:.35em}
.prose blockquote{
  margin:1.2em 0;
  padding:12px 18px;
  border-left:2px solid var(--amber);
  background:rgba(22,48,74,.55);
  color:var(--paper);
}

.figure-frame{
  position:relative;
  display:block;
  margin:0;
  overflow:hidden;
  background:var(--ink-700);
  border:1px solid var(--line);
}
.figure-frame img,
.figure-frame svg{
  display:block;
  width:100%;
  height:auto;
}
.figure-frame__caption{
  display:block;
  padding:10px 14px;
  border-top:1px solid var(--line);
  font-family:var(--mono);
  font-size:11px;
  line-height:1.6;
  letter-spacing:.08em;
  color:var(--steel);
}
.figure-frame--ratio{aspect-ratio:16 / 9}
.figure-frame--ratio img,
.figure-frame--ratio svg{height:100%;object-fit:cover}

body[data-version="v3"] .tag--current{
  color:var(--cinnabar-bright);
  border-color:rgba(226,80,59,.7);
  background:rgba(226,80,59,.1);
}

@media (max-width:1080px){
  .masthead__note{max-width:20ch}
  .footer-cols{grid-template-columns:repeat(2,minmax(0,1fr));gap:28px}
}

@media (max-width:900px){
  .nav-toggle{display:inline-flex}
  .quick-action{display:none}
  .masthead__note{display:none}
  .masthead__inner{grid-template-columns:minmax(0,1fr) auto;gap:12px}
  .brand{justify-items:start;text-align:left}
  .masthead__actions{gap:8px}
  .grid--aside{grid-template-columns:1fr}
  .site-nav{
    display:none;
    position:absolute;
    left:0;right:0;top:100%;
    max-height:calc(100vh - 84px);
    overflow-y:auto;
    background:var(--ink-800);
    border-top:1px solid var(--line);
    border-bottom:1px solid var(--line);
    box-shadow:var(--shadow-soft);
  }
  .site-nav[data-open="true"]{display:block}
  .nav-list{flex-direction:column;align-items:stretch;justify-content:flex-start}
  .nav-list__item{border-left:0;border-top:1px solid rgba(42,71,99,.6)}
  .nav-list__item:first-child{border-top:0}
  .nav-link{width:100%;padding:14px clamp(18px,5vw,24px);font-size:15px}
  .nav-link[aria-current="page"]::after{
    left:0;right:auto;top:0;bottom:0;
    width:2px;height:auto;
  }
  .nav-list__case{margin-left:0;border-left:0;border-top:1px solid rgba(240,179,60,.35)}
  .nav-case{width:100%;padding:15px clamp(18px,5vw,24px);font-size:15px}
  .scroll-meter{position:relative;z-index:1}
}

@media (max-width:720px){
  .grid--2,.grid--3{grid-template-columns:minmax(0,1fr)}
  .footer-base{justify-content:flex-start}
}

@media (max-width:640px){
  body{background-attachment:scroll,scroll,scroll}
  .toprail__index{display:none}
  .toprail__inner{justify-content:center;min-height:44px}
  .version-switch{width:100%;max-width:340px}
  .version-switch__btn{flex:1 1 50%;text-align:center;padding:9px 8px}
  .brand__sub{font-size:9.5px;letter-spacing:.2em}
  #main-content{scroll-margin-top:120px}
}

@media (max-width:560px){
  .footer-cols{grid-template-columns:minmax(0,1fr);gap:26px}
  .footer-tagline{font-size:22px}
  .btn{width:100%;justify-content:center}
  .footer-lead__cta{justify-self:stretch}
}

@media (prefers-reduced-motion: reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    animation-duration:.01ms !important;
    animation-iteration-count:1 !important;
    transition-duration:.01ms !important;
    transition-delay:0ms !important;
  }
  .panel:hover{transform:none}
  .scroll-meter__bar{transition:none}
  .skip-link{transition:none}
}