/* ============================================================
   /assets/site.css — 威廉希尔官网 共享外壳
   控制台墨绿 × 信号青 × 呼号橙
   ============================================================ */

/* ---------- 1. Reset ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth;scroll-padding-top:1.5rem}
body,h1,h2,h3,h4,p,ul,ol,figure,blockquote,dl,dd{margin:0}
ul[class],ol[class]{list-style:none;padding:0}
img,svg,video{display:block;max-width:100%}
button{font:inherit;color:inherit}
a{color:inherit}

/* ---------- 2. Tokens ---------- */
:root{
  --ink-900:#0C1F1A;
  --ink-800:#0E2620;
  --panel:#12302A;
  --brand-green:#0F5B3F;
  --teal:#2BE7C4;
  --orange:#FF7A3D;
  --mist:#BFE9DD;
  --paper:#F4FAF7;
  --gray:#6E8C84;

  --line:rgba(191,233,221,.16);
  --line-strong:rgba(43,231,196,.30);
  --grad-signal:linear-gradient(135deg,#0F5B3F 0%,#2BE7C4 100%);
  --grad-panel:linear-gradient(180deg,#12302A 0%,#0E2620 100%);

  --font-display:"Noto Sans SC","Source Han Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif;
  --font-body:"Noto Sans SC","Source Han Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif;
  --font-mono:"JetBrains Mono","Source Han Mono","SFMono-Regular",ui-monospace,Menlo,Consolas,monospace;

  --radius:6px;
  --shadow-panel:8px 8px 0 rgba(0,0,0,.38);
  --shadow-soft:0 18px 42px rgba(0,0,0,.35);
  --maxw:1180px;
  --pad-x:clamp(1rem,4vw,2.5rem);
}

/* ---------- 3. Base ---------- */
html{background-color:var(--ink-900)}
body{
  font-family:var(--font-body);
  font-size:clamp(15px,.6vw + 13px,17px);
  line-height:1.75;
  color:var(--paper);
  background-color:var(--ink-900);
  background-image:
    radial-gradient(1100px 560px at 10% -12%,rgba(15,91,63,.55),transparent 70%),
    radial-gradient(880px 480px at 102% -4%,rgba(43,231,196,.12),transparent 66%),
    repeating-linear-gradient(0deg,var(--line) 0 1px,transparent 1px 92px),
    repeating-linear-gradient(90deg,var(--line) 0 1px,transparent 1px 92px);
  background-attachment:fixed;
  -webkit-font-smoothing:antialiased;
  min-height:100vh;
}
h1,h2,h3,h4{font-family:var(--font-display);font-weight:900;line-height:1.08;letter-spacing:-.02em;text-wrap:balance}
h1{font-size:clamp(2.2rem,6vw,4.4rem)}
h2{font-size:clamp(1.5rem,3vw,2.3rem)}
h3{font-size:clamp(1.15rem,1.8vw,1.4rem);letter-spacing:-.01em}
p{max-width:72ch}
strong{font-weight:700;color:var(--paper)}
::selection{background:var(--teal);color:#06120F}

:focus-visible{outline:2px solid var(--teal);outline-offset:3px;border-radius:2px}
.btn:focus-visible,.chip:focus-visible{outline-color:var(--orange)}

/* ---------- 4. Utilities ---------- */
.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}
.mono{font-family:var(--font-mono);letter-spacing:.08em;font-size:.86em;color:var(--gray)}
.eyebrow{
  display:inline-flex;align-items:center;gap:.6rem;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.2em;text-transform:uppercase;
  color:var(--teal);
}
.eyebrow::before{content:"";width:24px;height:2px;background:var(--orange);flex:none}
.lede{font-size:clamp(1.02rem,1.5vw,1.22rem);line-height:1.7;color:var(--mist);max-width:62ch}
.link{
  color:var(--teal);text-decoration:none;
  border-bottom:1px solid rgba(43,231,196,.45);
  transition:border-color .18s ease,color .18s ease;
}
.link:hover{border-bottom-color:var(--teal);color:var(--paper)}

.wrap{width:min(100% - 2rem,var(--maxw));margin-inline:auto}
@media (min-width:768px){.wrap{width:min(100% - 4rem,var(--maxw))}}

.section{padding-block:clamp(1.75rem,4vw,3rem)}
.section__head{
  display:flex;flex-wrap:wrap;align-items:flex-end;justify-content:space-between;gap:1rem;
  margin-bottom:clamp(1rem,2.5vw,1.75rem);
}

/* ---------- 5. Skip link ---------- */
.skip-link{
  position:absolute;left:1rem;top:-4rem;z-index:300;
  padding:.6rem 1rem;
  background:var(--teal);color:#06120F;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;
  border-radius:4px;text-decoration:none;
  transition:top .2s ease;
}
.skip-link:focus{top:.6rem}

/* ---------- 6. Header frame ---------- */
.site-header{
  position:relative;z-index:60;
  background:linear-gradient(180deg,rgba(12,31,26,.98),rgba(12,31,26,.9));
  border-bottom:2px solid var(--line-strong);
  box-shadow:0 10px 30px rgba(0,0,0,.35);
}

.console-strip{
  display:flex;align-items:center;gap:clamp(.85rem,2.2vw,1.9rem);
  padding:.45rem var(--pad-x);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;text-transform:uppercase;
  color:var(--gray);
  overflow-x:auto;overflow-y:hidden;
  border-bottom:1px solid var(--line);
  background-image:
    repeating-linear-gradient(90deg,rgba(43,231,196,.16) 0 1px,transparent 1px 26px),
    linear-gradient(90deg,rgba(15,91,63,.55),rgba(12,31,26,.15) 65%);
}
.console-strip__item{display:inline-flex;align-items:center;gap:.5rem;white-space:nowrap}
.console-strip__item--live{color:var(--teal)}
.console-strip__item--batch{color:var(--orange);font-weight:700;letter-spacing:.22em}
.console-strip__spacer{flex:1 1 auto;min-width:.5rem}
.console-strip__dot{
  width:7px;height:7px;border-radius:50%;background:var(--orange);flex:none;
  animation:wh-signal 3.2s ease-out infinite;
}
@keyframes wh-signal{
  0%{box-shadow:0 0 0 0 rgba(255,122,61,.55)}
  70%{box-shadow:0 0 0 10px rgba(255,122,61,0)}
  100%{box-shadow:0 0 0 0 rgba(255,122,61,0)}
}

.frame{
  display:grid;
  grid-template-columns:minmax(0,1fr) auto;
  align-items:center;
  gap:.7rem 1.25rem;
  padding:.85rem var(--pad-x) 1rem;
}

/* Brand */
.brand{display:inline-flex;align-items:center;gap:.75rem;text-decoration:none;color:var(--paper);justify-self:start}
.brand__mark{
  display:grid;place-items:center;flex:none;
  width:46px;height:46px;
  border:2px solid var(--teal);border-radius:2px;
  background:rgba(43,231,196,.08);
  color:var(--teal);
  font-family:var(--font-mono);font-size:15px;font-weight:700;letter-spacing:.04em;
  box-shadow:3px 3px 0 rgba(0,0,0,.45);
}
.brand__text{display:block;min-width:0}
.brand__name{display:block;font-family:var(--font-display);font-weight:900;font-size:1.1rem;letter-spacing:-.01em;line-height:1.1}
.brand__tag{display:block;margin-top:.18rem;font-family:var(--font-mono);font-size:10px;letter-spacing:.24em;text-transform:uppercase;color:var(--gray)}

/* Toggle */
.nav-toggle{
  display:inline-flex;align-items:center;gap:.55rem;
  padding:.5rem .7rem;
  border:2px solid var(--line-strong);border-radius:4px;
  background:rgba(43,231,196,.06);color:var(--mist);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.16em;text-transform:uppercase;
  cursor:pointer;
  transition:background .18s ease,color .18s ease,border-color .18s ease;
}
.nav-toggle:hover{border-color:var(--teal);color:var(--paper)}
.nav-toggle[aria-expanded="true"]{background:var(--teal);color:#06120F;border-color:var(--teal)}
.nav-toggle__bars{display:inline-flex;flex-direction:column;justify-content:center;gap:3px;width:16px;height:12px}
.nav-toggle__bars i{display:block;height:2px;width:100%;background:currentColor;transition:transform .22s ease,opacity .22s ease}
.site-header[data-open] .nav-toggle__bars i:nth-child(1){transform:translateY(5px) rotate(45deg)}
.site-header[data-open] .nav-toggle__bars i:nth-child(2){opacity:0}
.site-header[data-open] .nav-toggle__bars i:nth-child(3){transform:translateY(-5px) rotate(-45deg)}

/* Nav shell */
.frame__nav{grid-column:1 / -1;display:none;flex-direction:column;gap:.9rem;padding-top:.35rem}
.site-header[data-open] .frame__nav{display:flex}

.nav-list{display:flex;flex-direction:column;gap:.15rem;margin:0;padding:0;list-style:none}
.nav-list__link{
  display:flex;flex-direction:column;gap:.15rem;
  padding:.6rem .7rem;
  color:var(--mist);text-decoration:none;
  font-size:.95rem;font-weight:600;line-height:1.2;
  border-bottom:2px solid transparent;
  border-left:2px solid transparent;
  transition:background .18s ease,color .18s ease,border-color .18s ease;
}
.nav-list__num{font-family:var(--font-mono);font-size:9px;letter-spacing:.2em;color:var(--gray)}
.nav-list__link:hover{color:var(--paper);background:rgba(43,231,196,.09);border-left-color:var(--teal)}
.nav-list__link[aria-current="page"]{
  color:var(--teal);
  background:rgba(43,231,196,.1);
  border-left-color:var(--orange);
  border-bottom-color:transparent;
}
.nav-list__link[aria-current="page"] .nav-list__num{color:var(--orange)}
.nav-list__link:focus-visible{outline-offset:-2px;background:rgba(43,231,196,.12)}

/* Util cluster */
.frame__util{display:flex;flex-direction:column;align-items:stretch;gap:.6rem;padding-top:.8rem;border-top:1px dashed var(--line)}
.frame__util .btn{width:100%}

.chip{
  display:inline-flex;align-items:center;justify-content:center;gap:.5rem;
  padding:.42rem .8rem;
  border:1px solid var(--line-strong);border-radius:999px;
  background:rgba(43,231,196,.07);
  color:var(--mist);text-decoration:none;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;text-transform:uppercase;
  transition:color .18s ease,border-color .18s ease,background .18s ease;
}
.chip:hover{color:var(--paper);border-color:var(--teal);background:rgba(43,231,196,.14)}
.chip__dot{
  width:6px;height:6px;border-radius:50%;background:var(--teal);flex:none;
  animation:wh-signal-soft 3.2s ease-out infinite;
}
@keyframes wh-signal-soft{
  0%{box-shadow:0 0 0 0 rgba(43,231,196,.55)}
  70%{box-shadow:0 0 0 8px rgba(43,231,196,0)}
  100%{box-shadow:0 0 0 0 rgba(43,231,196,0)}
}

@media (min-width:900px){
  .frame{grid-template-columns:auto minmax(0,1fr);gap:1rem 1.75rem;padding-block:1rem}
  .nav-toggle{display:none}
  .frame__nav{
    grid-column:2;display:flex;flex-direction:row;align-items:center;justify-content:flex-end;
    flex-wrap:wrap;gap:.9rem 1.1rem;padding-top:0;
  }
  .nav-list{flex-direction:row;flex-wrap:wrap;gap:.1rem}
  .nav-list__link{border-bottom:2px solid transparent;border-left:0;padding:.5rem .7rem .55rem}
  .nav-list__link:hover{border-left-color:transparent;border-bottom-color:var(--teal)}
  .nav-list__link[aria-current="page"]{border-left-color:transparent;border-bottom-color:var(--orange)}
  .frame__util{
    flex-direction:row;align-items:center;
    padding-top:0;padding-left:1rem;border-top:0;border-left:1px solid var(--line);
  }
  .frame__util .btn{width:auto}
}

/* ---------- 7. Buttons ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:.5rem;
  padding:.8rem 1.2rem;
  border:2px solid var(--teal);border-radius:4px;
  background:var(--brand-green);color:var(--paper);
  font-family:var(--font-display);font-weight:700;font-size:.94rem;letter-spacing:.02em;
  text-decoration:none;cursor:pointer;
  box-shadow:4px 4px 0 rgba(0,0,0,.45);
  transition:transform .18s ease,box-shadow .18s ease,background .18s ease,color .18s ease,border-color .18s ease;
}
.btn:hover{transform:translate(-1px,-1px);box-shadow:6px 6px 0 rgba(0,0,0,.5)}
.btn:active{transform:translate(2px,2px);box-shadow:1px 1px 0 rgba(0,0,0,.5)}
.btn--signal{
  background:transparent;border-color:var(--orange);color:var(--orange);
  box-shadow:4px 4px 0 rgba(255,122,61,.2);
  font-family:var(--font-mono);font-size:.82rem;letter-spacing:.08em;
}
.btn--signal:hover{background:var(--orange);color:#0C1F1A;box-shadow:6px 6px 0 rgba(255,122,61,.28)}
.btn--ghost{
  background:transparent;border-color:var(--line-strong);color:var(--mist);
  box-shadow:none;font-family:var(--font-mono);font-size:.8rem;letter-spacing:.1em;
}
.btn--ghost:hover{border-color:var(--teal);color:var(--paper);background:rgba(43,231,196,.1);transform:none;box-shadow:none}

/* ---------- 8. Grid & container ---------- */
.grid{display:grid;gap:clamp(1rem,2.4vw,1.75rem)}
.grid--2{grid-template-columns:repeat(auto-fit,minmax(min(100%,320px),1fr))}
.grid--3{grid-template-columns:repeat(auto-fit,minmax(min(100%,250px),1fr))}
.grid--rail{grid-template-columns:minmax(0,1fr)}
@media (min-width:1024px){
  .grid--rail{grid-template-columns:220px minmax(0,1fr);gap:clamp(1.5rem,3vw,2.5rem);align-items:start}
}

/* ---------- 9. Panels ---------- */
.panel{
  position:relative;
  padding:clamp(1.2rem,3vw,2.25rem);
  background:var(--grad-panel);
  border:2px solid var(--line-strong);
  border-radius:var(--radius);
  box-shadow:var(--shadow-panel),var(--shadow-soft);
}
.panel--flat{border-color:var(--line);box-shadow:none;background:rgba(18,48,42,.6)}
.panel__head{
  display:flex;flex-wrap:wrap;align-items:baseline;justify-content:space-between;gap:.5rem 1rem;
  padding-bottom:.8rem;margin-bottom:1.2rem;
  border-bottom:1px dashed var(--line);
}
.panel__label{font-family:var(--font-mono);font-size:11px;letter-spacing:.18em;text-transform:uppercase;color:var(--gray)}

/* ---------- 10. Research board ---------- */
.research{
  display:grid;gap:1.4rem;
  padding:clamp(1.25rem,3vw,2.25rem);
  border:2px solid var(--teal);border-radius:var(--radius);
  background:linear-gradient(180deg,rgba(18,48,42,.96),rgba(12,31,26,.99));
  box-shadow:var(--shadow-panel),0 0 0 1px rgba(12,31,26,.6) inset;
}
.research__title{font-size:clamp(1.25rem,2.2vw,1.7rem)}
.research__abstract{border-left:3px solid var(--orange);padding-left:1rem;color:var(--mist)}
.research__evidence{border-top:2px solid var(--line-strong);padding-top:1.1rem;display:grid;gap:.9rem}
.research__terms{display:grid;gap:.5rem;font-size:.94rem;color:var(--mist)}
.research__further{
  border-top:1px dashed var(--line);padding-top:1rem;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.08em;color:var(--gray);
}

/* ---------- 11. Figures (image containers) ---------- */
.figure{display:grid;gap:.6rem;margin:0}
.figure__frame{
  position:relative;overflow:hidden;
  aspect-ratio:16 / 10;
  border:2px solid var(--line-strong);border-radius:var(--radius);
  background:linear-gradient(150deg,#12302A,#0C1F1A);
  box-shadow:6px 6px 0 rgba(0,0,0,.35);
}
.figure__frame::after{
  content:"";position:absolute;inset:0;pointer-events:none;
  background-image:
    linear-gradient(rgba(43,231,196,.07) 1px,transparent 1px),
    linear-gradient(90deg,rgba(43,231,196,.07) 1px,transparent 1px);
  background-size:28px 28px;
}
.figure__img{width:100%;height:100%;object-fit:cover;display:block}
.figure__caption{font-family:var(--font-mono);font-size:11px;letter-spacing:.1em;text-transform:uppercase;color:var(--gray)}
.figure--wide .figure__frame{aspect-ratio:21 / 9}
.figure--square .figure__frame{aspect-ratio:1 / 1}
.figure--tall .figure__frame{aspect-ratio:4 / 5}

/* ---------- 12. Breadcrumbs / TOC / rail ---------- */
.breadcrumbs{display:flex;flex-wrap:wrap;align-items:center;gap:.4rem;margin:0;padding:0;list-style:none;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--gray)}
.breadcrumbs__item{display:inline-flex;align-items:center;gap:.5rem}
.breadcrumbs__item:not(:last-child)::after{content:"/";color:rgba(43,231,196,.5)}
.breadcrumbs a{color:var(--mist);text-decoration:none}
.breadcrumbs a:hover{color:var(--teal)}
.breadcrumbs [aria-current="page"]{color:var(--teal)}

.toc{font-family:var(--font-mono);font-size:11px;letter-spacing:.12em;text-transform:uppercase}
.toc--sticky{position:sticky;top:1.5rem}
.toc__list{display:grid;gap:.2rem;margin:0;padding:0;list-style:none}
.toc__link{
  display:flex;gap:.6rem;align-items:baseline;
  padding:.4rem .6rem;
  color:var(--gray);text-decoration:none;
  border-left:2px solid transparent;
  transition:color .18s ease,background .18s ease,border-color .18s ease;
}
.toc__link:hover{color:var(--paper);background:rgba(43,231,196,.07)}
.toc__link.is-active{color:var(--teal);border-left-color:var(--orange);background:rgba(43,231,196,.1)}
.toc__num{color:rgba(255,122,61,.85)}

.rail{position:relative;padding-left:1rem;border-left:1px dashed var(--line)}

/* ---------- 13. Notes / tags / stats / scale / filters ---------- */
.note{
  border-left:2px solid var(--teal);
  background:rgba(43,231,196,.07);
  padding:.75rem 1rem;border-radius:0 4px 4px 0;
  font-size:.92rem;color:var(--mist);
}
.notice{
  border-left:3px solid var(--orange);
  background:rgba(255,122,61,.09);
  padding:.8rem 1rem;border-radius:0 4px 4px 0;
  font-size:.92rem;color:var(--mist);
}
.tag{
  display:inline-flex;align-items:center;gap:.35rem;
  padding:.24rem .5rem;border:1px solid var(--line-strong);border-radius:2px;
  font-family:var(--font-mono);font-size:10px;letter-spacing:.16em;text-transform:uppercase;
  color:var(--teal);
}
.tag--signal{color:var(--orange);border-color:rgba(255,122,61,.45)}

.stat{display:grid;gap:.2rem}
.stat__value{font-family:var(--font-display);font-weight:900;font-size:clamp(1.8rem,4vw,2.6rem);line-height:1;letter-spacing:-.03em;color:var(--teal)}
.stat__label{font-family:var(--font-mono);font-size:11px;letter-spacing:.16em;text-transform:uppercase;color:var(--gray)}

.scale{display:flex;align-items:flex-end;gap:6px;height:18px}
.scale__tick{display:block;width:2px;height:8px;background:rgba(43,231,196,.45)}
.scale__tick--tall{height:16px;background:var(--orange)}

.filter-bar{display:flex;flex-wrap:wrap;gap:.5rem}
.filter-btn{
  padding:.42rem .75rem;
  border:1px solid rgba(191,233,221,.28);border-radius:2px;
  background:transparent;color:var(--mist);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;text-transform:uppercase;
  cursor:pointer;transition:background .18s ease,color .18s ease,border-color .18s ease;
}
.filter-btn:hover{border-color:var(--teal);color:var(--paper)}
.filter-btn[aria-pressed="true"]{background:var(--teal);color:#06120F;border-color:var(--teal)}

/* ---------- 14. Footer ---------- */
.site-footer{
  position:relative;
  margin-top:clamp(2.5rem,6vw,4.5rem);
  border-top:2px solid var(--line-strong);
  background:linear-gradient(180deg,#0E2620 0%,#0A1A16 100%);
}
.footer__scale{
  display:block;height:10px;opacity:.7;
  background-image:repeating-linear-gradient(90deg,rgba(43,231,196,.4) 0 2px,transparent 2px 28px);
}
.footer__grid{
  display:grid;grid-template-columns:minmax(0,1fr);gap:clamp(1.5rem,3vw,2.4rem);
  padding:clamp(2rem,5vw,3.25rem) 0 1.75rem;
}
@media (min-width:640px){.footer__grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media (min-width:1024px){.footer__grid{grid-template-columns:1.5fr 1fr 1fr 1.15fr}}

.footer__col{display:grid;align-content:start;gap:.9rem}
.footer__col--brand .brand{margin-bottom:.2rem}
.footer__title{
  display:flex;align-items:center;gap:.5rem;
  font-family:var(--font-mono);font-size:11px;font-weight:700;letter-spacing:.2em;text-transform:uppercase;
  color:var(--paper);
}
.footer__title::before{content:"";width:14px;height:2px;background:var(--orange);flex:none}
.footer__text{font-size:.92rem;line-height:1.7;color:var(--mist);max-width:34ch}
.footer__list{display:grid;gap:.45rem;margin:0;padding:0;list-style:none}
.footer__link{
  display:inline-block;width:fit-content;
  color:var(--mist);text-decoration:none;font-size:.92rem;
  border-bottom:1px solid transparent;
  transition:color .18s ease,border-color .18s ease;
}
.footer__link:hover{color:var(--teal);border-bottom-color:rgba(43,231,196,.6)}
.footer__contact{display:grid;gap:.4rem;font-size:.9rem;color:var(--mist);word-break:break-word}
.footer__contact span{display:block;line-height:1.6}

.footer__legal{
  display:flex;flex-wrap:wrap;gap:.6rem 1.4rem;
  padding:1.1rem 0;
  border-top:1px dashed var(--line);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.12em;text-transform:uppercase;
}
.footer__bar{
  display:flex;flex-wrap:wrap;justify-content:space-between;gap:.6rem 1.5rem;
  padding:1rem 0 1.75rem;
  border-top:1px dashed var(--line);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.1em;
  color:var(--gray);
}

/* ---------- 15. Motion: reveal / progress / to-top ---------- */
html.js [data-reveal]{
  opacity:0;transform:translateY(12px);
  transition:opacity .42s cubic-bezier(.2,.7,.2,1),transform .42s cubic-bezier(.2,.7,.2,1);
}
html.js [data-reveal][data-seen]{opacity:1;transform:none}

.progress{
  position:fixed;top:0;left:0;right:0;height:3px;z-index:120;
  background:rgba(191,233,221,.12);pointer-events:none;
}
.progress__bar{
  display:block;height:100%;width:0;
  background:var(--grad-signal);
  box-shadow:0 0 12px rgba(43,231,196,.7);
}

.to-top{
  position:fixed;right:clamp(.8rem,3vw,1.6rem);bottom:clamp(.8rem,3vw,1.6rem);z-index:110;
  display:inline-flex;align-items:center;gap:.45rem;
  padding:.6rem .8rem;
  border:2px solid var(--teal);border-radius:4px;
  background:rgba(12,31,26,.94);color:var(--teal);
  font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;text-transform:uppercase;
  cursor:pointer;
  opacity:0;transform:translateY(10px);pointer-events:none;
  transition:opacity .24s ease,transform .24s ease,background .18s ease,color .18s ease;
}
.to-top[data-visible]{opacity:1;transform:none;pointer-events:auto}
.to-top:hover{background:var(--teal);color:#06120F}

/* ---------- 16. Reduced motion ---------- */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    animation-duration:.001ms !important;
    animation-iteration-count:1 !important;
    transition-duration:.001ms !important;
  }
  html.js [data-reveal]{opacity:1 !important;transform:none !important}
  .to-top{transform:none}
}