:root{
  --orange:#F26B1D;
  --orange-lit:#FFB25E;
  --ink:#0B1A2E;
  --ink-2:#16283F;
  --paper:#F7F5F0;
  --paper-2:#EDEAE2;
  --text:#1B2330;
  --slate:#5C6B7F;
  --line:#D8D3C8;
  --line-soft:rgba(216,211,200,.55);
  --line-dark:rgba(247,245,240,.14);
  --star-1:#C0392B;
  --star-2:#B7791F;
  --star-3:#4C7A34;
  --star-4:#14707A;
  --star-5:#2C4C9C;
  --star-6:#5B3A8E;
  --star-7:#8E2C4A;
  --gutter:clamp(20px,4.5vw,96px);
  --maxw:1440px;
  --header-h:68px;
  --radius:2px;
  --shadow-1:0 1px 0 rgba(27,35,48,.06);
  --shadow-2:0 8px 22px -12px rgba(11,26,46,.5);
  --font-sans:"Noto Sans SC","Source Han Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,-apple-system,"Segoe UI",sans-serif;
  --font-mono:"IBM Plex Mono","JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  scroll-padding-top:calc(var(--header-h) + 20px);
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,h5,p,ul,ol,li,figure,blockquote,dl,dd{margin:0}
ul,ol{padding:0;list-style:none}
img,picture,svg,video{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
button{font:inherit;color:inherit;background:none;border:0;cursor:pointer}
input,select,textarea{font:inherit;color:inherit}

body{
  font-family:var(--font-sans);
  font-size:16px;
  line-height:1.75;
  color:var(--text);
  background-color:var(--paper);
  background-image:
    linear-gradient(to right,var(--line-soft) 1px,transparent 1px),
    linear-gradient(to bottom,var(--line-soft) 1px,transparent 1px);
  background-size:96px 96px;
  -webkit-font-smoothing:antialiased;
}
@media (min-width:768px){body{font-size:17px}}

h1,h2,h3,h4{line-height:1.2;font-weight:800;letter-spacing:-.01em}
strong,b{font-weight:700}

a:focus-visible,
button:focus-visible,
[tabindex]:focus-visible{
  outline:2px solid var(--orange);
  outline-offset:2px;
  border-radius:var(--radius);
}

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

.container{
  width:100%;
  max-width:var(--maxw);
  margin-inline:auto;
  padding-inline:var(--gutter);
}

.mono{font-family:var(--font-mono);font-variant-numeric:tabular-nums;letter-spacing:.02em}

.eyebrow{
  display:inline-flex;align-items:center;gap:10px;
  font-size:11px;letter-spacing:.16em;color:var(--slate);
}
.eyebrow::before{content:"";width:24px;height:1px;background:var(--orange)}
.surface-dark .eyebrow{color:rgba(247,245,240,.62)}

.display{
  font-weight:900;
  font-size:clamp(44px,9vw,120px);
  line-height:.94;
  letter-spacing:-.02em;
  transform:skewX(-1.5deg);
}
.sec-index{
  display:block;
  font-family:var(--font-mono);
  font-size:12px;
  letter-spacing:.16em;
  color:var(--orange);
}

.skip-link{
  position:absolute;left:var(--gutter);top:8px;z-index:120;
  padding:10px 16px;
  background:var(--orange);color:var(--ink);
  font-size:14px;font-weight:700;border-radius:var(--radius);
  transform:translateY(-220%);
  transition:transform .16s ease;
}
.skip-link:focus{transform:none}

/* ---------- header ---------- */
.site-header{
  position:sticky;top:0;z-index:80;
  background-color:rgba(11,26,46,.58);
  -webkit-backdrop-filter:blur(10px) saturate(130%);
  backdrop-filter:blur(10px) saturate(130%);
  border-bottom:1px solid rgba(247,245,240,.1);
  transition:background-color .24s ease,border-color .24s ease,box-shadow .24s ease;
}
.site-header[data-scrolled="true"]{
  background-color:var(--ink);
  border-bottom-color:rgba(242,107,29,.42);
  box-shadow:0 14px 34px -26px rgba(11,26,46,.95);
}
.header-progress{
  position:absolute;left:0;right:0;bottom:-1px;height:2px;
  background:transparent;overflow:hidden;
}
.header-progress > span{
  display:block;width:100%;height:100%;
  background:linear-gradient(90deg,var(--orange),var(--orange-lit));
  transform:scaleX(0);transform-origin:0 50%;
}
.header-inner{
  position:relative;
  display:flex;align-items:center;
  gap:clamp(14px,2vw,40px);
  min-height:var(--header-h);
  padding-block:10px;
}
.brand{display:flex;align-items:center;gap:12px;flex:0 0 auto}
.brand__mark{
  display:grid;place-items:center;
  width:34px;height:34px;flex:0 0 auto;
  border:1px solid var(--orange);border-radius:var(--radius);
  background:rgba(242,107,29,.1);
  color:var(--orange);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.06em;
}
.brand__text{display:block}
.brand__name{display:block;font-size:18px;font-weight:800;letter-spacing:.02em;color:var(--paper)}
.brand__tagline{display:block;margin-top:2px;font-size:11px;letter-spacing:.1em;color:rgba(247,245,240,.6)}

.primary-nav{margin-left:auto;display:flex;align-items:center;gap:clamp(14px,2vw,36px)}
.primary-nav__list{display:flex;align-items:center;gap:clamp(8px,1.5vw,24px)}
.nav-link{
  position:relative;display:inline-flex;align-items:center;
  min-height:44px;padding:0 2px;
  font-size:13.5px;letter-spacing:.06em;
  color:rgba(247,245,240,.76);
  transition:color .16s ease;
}
.nav-link::after{
  content:"";position:absolute;left:2px;right:2px;bottom:8px;height:2px;
  background:var(--orange);
  transform:scaleX(0);transform-origin:0 50%;
  transition:transform .18s ease;
}
.nav-link:hover{color:var(--paper)}
.nav-link:hover::after{transform:scaleX(1)}
.nav-link[aria-current="page"]{color:var(--paper);font-weight:700}
.nav-link[aria-current="page"]::after{transform:scaleX(1);background:var(--orange-lit)}

.header-actions{
  display:flex;align-items:center;gap:10px;
  padding-left:clamp(10px,1.8vw,26px);
  border-left:1px solid var(--line-dark);
}
.quick-link{
  display:inline-flex;align-items:center;justify-content:center;
  min-height:44px;padding:0 14px;
  font-size:13px;letter-spacing:.04em;
  color:var(--paper);
  border:1px solid rgba(247,245,240,.28);
  border-radius:var(--radius);
  transition:background-color .16s ease,color .16s ease,border-color .16s ease,transform .16s ease;
}
.quick-link:hover{
  background:rgba(255,178,94,.16);
  border-color:var(--orange-lit);
  transform:translateY(-2px);
}
.quick-link--solid{
  background:var(--orange);border-color:var(--orange);
  color:var(--ink);font-weight:700;
}
.quick-link--solid:hover{background:var(--orange-lit);border-color:var(--orange-lit);color:var(--ink)}

.nav-toggle{
  display:none;align-items:center;gap:10px;
  margin-left:auto;
  min-height:44px;min-width:44px;padding:0 12px;
  border:1px solid rgba(247,245,240,.28);
  border-radius:var(--radius);
  color:var(--paper);
}
.nav-toggle__label{font-size:11px;letter-spacing:.16em}
.nav-toggle__bars{display:grid;gap:4px;width:16px}
.nav-toggle__bars span{
  display:block;height:2px;background:currentColor;
  transition:transform .18s ease,opacity .18s ease;
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:nth-child(1){transform:translateY(6px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:nth-child(2){opacity:0}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:nth-child(3){transform:translateY(-6px) rotate(-45deg)}
.nav-toggle:hover{border-color:var(--orange-lit);color:var(--orange-lit)}

/* ---------- footer ---------- */
.site-footer{
  position:relative;
  color:var(--paper);
  background-color:var(--ink);
  background-image:
    linear-gradient(to right,rgba(247,245,240,.06) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(247,245,240,.06) 1px,transparent 1px);
  background-size:96px 96px;
  border-top:1px solid rgba(242,107,29,.42);
}
.footer-grid{
  display:grid;
  grid-template-columns:1fr;
  gap:clamp(28px,3vw,52px);
  padding-block:clamp(44px,6.5vw,88px);
}
.footer-brand__desc{
  margin-top:18px;
  max-width:34ch;
  font-size:13.5px;
  line-height:1.8;
  color:rgba(247,245,240,.62);
}
.footer-col__title{
  position:relative;
  padding-bottom:12px;
  margin-bottom:16px;
  font-size:11px;font-weight:400;letter-spacing:.16em;
  color:var(--orange-lit);
}
.footer-col__title::after{
  content:"";position:absolute;left:0;bottom:0;
  width:22px;height:1px;background:var(--orange);
}
.footer-links li + li{margin-top:10px}
.footer-links a{
  display:inline-block;
  font-size:14px;
  color:rgba(247,245,240,.72);
  transition:color .16s ease,transform .16s ease;
}
.footer-links a:hover{color:var(--orange-lit);transform:translateY(-2px)}
.footer-contact__list{display:grid;gap:12px}
.footer-contact__list li{display:grid;gap:3px}
.footer-contact__k{
  font-size:11px;letter-spacing:.14em;color:rgba(247,245,240,.45);
}
.footer-contact__v{
  font-size:14px;line-height:1.6;color:rgba(247,245,240,.86);
}
.footer-note{
  margin-top:18px;
  padding-left:12px;
  border-left:2px solid var(--orange);
  font-size:12px;line-height:1.75;
  color:rgba(247,245,240,.55);
}
.footer-bottom{
  display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;
  gap:10px 28px;
  padding-block:20px;
  border-top:1px solid var(--line-dark);
  font-size:12px;
  color:rgba(247,245,240,.55);
}
.footer-bottom__links{display:flex;flex-wrap:wrap;gap:18px}
.footer-bottom__links a{color:rgba(247,245,240,.62)}
.footer-bottom__links a:hover{color:var(--orange-lit);text-decoration:underline}
.footer-legal{letter-spacing:.02em}
.footer-year{color:rgba(247,245,240,.45)}

/* ---------- buttons ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:10px;
  min-height:48px;padding:0 22px;
  border:1px solid transparent;border-radius:var(--radius);
  font-size:15px;font-weight:700;letter-spacing:.02em;
  transition:transform .16s ease,background-color .16s ease,color .16s ease,border-color .16s ease,box-shadow .16s ease;
}
.btn:hover{transform:translateY(-2px);box-shadow:var(--shadow-2)}
.btn:active{transform:translateY(0)}
.btn--primary{background:var(--orange);color:var(--ink)}
.btn--primary:hover{background:var(--orange-lit)}
.btn--outline{border-color:var(--ink);color:var(--ink)}
.btn--outline:hover{background:var(--ink);color:var(--paper)}
.btn--ghost-dark{border-color:rgba(247,245,240,.4);color:var(--paper)}
.btn--ghost-dark:hover{background:var(--paper);color:var(--ink);border-color:var(--paper)}
.btn--sm{min-height:40px;padding:0 16px;font-size:13.5px}

/* ---------- surfaces ---------- */
.surface-dark{
  background-color:var(--ink);
  background-image:
    linear-gradient(to right,rgba(247,245,240,.06) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(247,245,240,.06) 1px,transparent 1px);
  background-size:96px 96px;
  color:var(--paper);
}
.surface-paper{background-color:var(--paper);color:var(--text)}
.section{padding-block:clamp(48px,7vw,96px)}
.section--tight{padding-block:clamp(28px,4vw,56px)}
.section__head{display:flex;flex-direction:column;gap:12px;margin-bottom:clamp(24px,3vw,44px)}
.section__title{font-size:clamp(26px,4.2vw,52px);font-weight:900;letter-spacing:-.02em;transform:skewX(-1.5deg)}
.section__rule{height:1px;border:0;background:var(--line);margin:0}
.surface-dark .section__rule,
.site-footer .section__rule{background:var(--line-dark)}

.panel{
  position:relative;
  padding:clamp(20px,2.4vw,32px);
  background:var(--paper);
  border:1px solid var(--line);
  border-radius:var(--radius);
  box-shadow:var(--shadow-1);
}
.panel::before{
  content:"";position:absolute;inset:4px;
  border:1px solid var(--line-soft);
  pointer-events:none;
}
.panel--dark{
  background:var(--ink-2);
  border-color:var(--line-dark);
  color:var(--paper);
}
.panel--dark::before{border-color:rgba(247,245,240,.08)}

.tag{
  display:inline-flex;align-items:center;justify-content:center;
  min-height:22px;padding:0 8px;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.08em;
  border:1px solid currentColor;border-radius:var(--radius);
  background:rgba(247,245,240,.6);
}
.tag--1{color:var(--star-1)}
.tag--2{color:var(--star-2)}
.tag--3{color:var(--star-3)}
.tag--4{color:var(--star-4)}
.tag--5{color:var(--star-5)}
.tag--6{color:var(--star-6)}
.tag--7{color:var(--star-7)}

.img-frame{
  position:relative;display:block;overflow:hidden;
  background-color:var(--paper-2);
  background-image:repeating-linear-gradient(135deg,rgba(216,211,200,.7) 0 1px,transparent 1px 14px);
  border:1px solid var(--line);
  border-radius:var(--radius);
}
.img-frame > img,
.img-frame > picture,
.img-frame > picture > img{width:100%;height:100%}
.img-frame > img,
.img-frame > picture > img{object-fit:cover}
.img-frame--3x4{aspect-ratio:3/4}
.img-frame--4x3{aspect-ratio:4/3}
.img-frame--16x9{aspect-ratio:16/9}
.img-frame--square{aspect-ratio:1/1}
.img-frame__cap{
  position:absolute;left:0;bottom:0;
  padding:6px 10px;
  background:var(--ink);color:var(--paper);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.06em;
}
.img-frame__tag{position:absolute;top:10px;left:10px}

.breadcrumb{
  padding-block:14px;
  border-bottom:1px solid var(--line);
  font-size:12px;color:var(--slate);
}
.breadcrumb__list{display:flex;flex-wrap:wrap;align-items:center}
.breadcrumb__item{display:inline-flex;align-items:center}
.breadcrumb__item:not(:last-child)::after{content:"/";margin:0 8px;color:var(--line)}
.breadcrumb__link{color:var(--slate)}
.breadcrumb__link:hover{color:var(--orange);text-decoration:underline}
.breadcrumb__current{color:var(--text);font-weight:600}

.prose{max-width:72ch;font-size:16.5px;line-height:1.75;color:var(--text)}
@media (min-width:768px){.prose{font-size:17px}}
.prose > * + *{margin-top:1.05em}
.prose h2{font-size:clamp(22px,2.6vw,30px);margin-top:2em}
.prose h3{font-size:19px;margin-top:1.7em;font-weight:700}
.prose ul,.prose ol{padding-left:1.4em;list-style:disc}
.prose ol{list-style:decimal}
.prose li + li{margin-top:.45em}
.prose li::marker{color:var(--orange)}
.prose a{color:var(--orange);text-decoration:underline;text-underline-offset:3px}
.prose blockquote{padding-left:16px;border-left:2px solid var(--orange);color:var(--slate)}
.prose code{
  padding:2px 6px;border-radius:var(--radius);
  background:var(--paper-2);
  font-family:var(--font-mono);font-size:.9em;
}

.grid{display:grid;gap:clamp(16px,2vw,24px)}
.grid--12{grid-template-columns:repeat(12,minmax(0,1fr))}
.span-3,.span-4,.span-5,.span-6,.span-7,.span-8,.span-9,.span-12{grid-column:1/-1}
@media (min-width:900px){
  .span-3{grid-column:span 3}
  .span-4{grid-column:span 4}
  .span-5{grid-column:span 5}
  .span-6{grid-column:span 6}
  .span-7{grid-column:span 7}
  .span-8{grid-column:span 8}
  .span-9{grid-column:span 9}
  .span-12{grid-column:span 12}
}

.toc__list{display:flex;flex-direction:column;gap:2px}
.toc__item{display:block}
.toc__link{
  display:flex;align-items:baseline;gap:10px;
  min-height:40px;padding:8px 10px;
  border-left:2px solid var(--line);
  font-size:13px;color:var(--slate);
  transition:color .16s ease,border-color .16s ease,background-color .16s ease;
}
.toc__link:hover{color:var(--text);border-left-color:var(--orange);background:var(--paper-2)}
.toc__link[aria-current="location"]{
  color:var(--ink);border-left-color:var(--orange);
  background:var(--paper-2);font-weight:700;
}
.toc__num{font-family:var(--font-mono);font-size:11px;color:var(--orange)}

.to-top{
  position:fixed;right:clamp(12px,2vw,28px);bottom:clamp(12px,2vw,28px);z-index:70;
  display:grid;place-items:center;
  width:46px;height:46px;
  background:var(--ink);color:var(--paper);
  border:1px solid rgba(247,245,240,.22);
  border-radius:var(--radius);
  font-family:var(--font-mono);font-size:12px;
  opacity:0;visibility:hidden;transform:translateY(6px);
  transition:opacity .2s ease,transform .2s ease,visibility .2s ease,background-color .16s ease,color .16s ease;
}
.to-top[data-visible="true"]{opacity:1;visibility:visible;transform:none}
.to-top:hover{background:var(--orange);border-color:var(--orange);color:var(--ink)}

html.nav-open{overflow:hidden}

/* ---------- responsive ---------- */
@media (min-width:640px){
  .footer-grid{grid-template-columns:1fr 1fr}
}
@media (min-width:1024px){
  .footer-grid{grid-template-columns:1.5fr .85fr .85fr .85fr 1.6fr}
}
@media (max-width:1024px){
  .site-header{
    -webkit-backdrop-filter:none;
    backdrop-filter:none;
    background-color:var(--ink);
  }
  .nav-toggle{display:inline-flex}
  .primary-nav{
    position:fixed;inset:0;z-index:70;
    display:block;
    margin:0;
    padding:calc(var(--header-h) + 24px) var(--gutter) 40px;
    background-color:var(--ink);
    background-image:
      linear-gradient(to right,rgba(247,245,240,.06) 1px,transparent 1px),
      linear-gradient(to bottom,rgba(247,245,240,.06) 1px,transparent 1px);
    background-size:96px 96px;
    overflow-y:auto;
    opacity:0;visibility:hidden;pointer-events:none;
    transform:translateY(-10px);
    transition:opacity .2s ease,transform .2s ease,visibility .2s ease;
  }
  .primary-nav[data-open="true"]{
    opacity:1;visibility:visible;pointer-events:auto;transform:none;
  }
  .primary-nav__list{display:block;counter-reset:nav;border-top:1px solid var(--line-dark)}
  .primary-nav__item{
    counter-increment:nav;
    border-bottom:1px solid var(--line-dark);
  }
  .nav-link{
    display:flex;align-items:center;justify-content:space-between;
    min-height:64px;padding:0 2px;
    font-size:20px;font-weight:800;letter-spacing:.02em;
    color:var(--paper);
  }
  .nav-link::after{display:none}
  .nav-link::before{
    content:"0" counter(nav);
    order:2;
    font-family:var(--font-mono);font-size:12px;
    color:var(--orange);letter-spacing:.06em;
  }
  .nav-link[aria-current="page"]{color:var(--orange-lit)}
  .header-actions{
    display:flex;flex-wrap:wrap;gap:12px;
    margin-top:32px;padding-left:0;border-left:0;
  }
  .quick-link{flex:1 1 45%;min-height:52px;font-size:15px}
}
@media (max-width:420px){
  .brand__tagline{display:none}
  .footer-bottom{flex-direction:column;align-items:flex-start}
}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    transition-duration:.01ms !important;
    animation-duration:.01ms !important;
    animation-iteration-count:1 !important;
  }
  .btn:hover,.quick-link:hover,.footer-links a:hover{transform:none}
}