/* ============================================================
   U体育赛场 · /assets/site.css
   共享外壳：转播导轨头部、信息牌页脚、基础排版与通用组件
   ============================================================ */

/* ---------- 1. 设计令牌 ---------- */
:root{
  --ink:#08101D;
  --ink-2:#0F1B2D;
  --glass:#16263D;
  --cyan:#38E1E6;
  --orange:#FF7A1A;
  --white:#F4F7FB;
  --green:#3DDC97;
  --yellow:#F2C94C;
  --mist:#7C8DA6;
  --black:#050A12;

  --body-text:#D5E0EE;
  --rail:88px;
  --bar:64px;
  --shell:1440px;

  --font-serif:"Noto Serif SC","Source Han Serif SC","Songti SC","SimSun",Georgia,serif;
  --font-sans:"Noto Sans SC","Source Han Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --font-mono:"IBM Plex Mono","DIN Condensed",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;

  --line-soft:rgba(124,141,166,.18);
  --line-cyan:rgba(56,225,230,.34);
}

/* ---------- 2. reset ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,h5,p,figure,blockquote,dl,dd,ul,ol{margin:0}
ul,ol{padding:0;list-style:none}
img,svg,video{display:block;max-width:100%}
button{font:inherit;color:inherit;background:none;border:0;padding:0;cursor:pointer}
a{color:inherit;text-decoration:none}
table{border-collapse:collapse;width:100%}

/* ---------- 3. 基础排版与页面底色 ---------- */
body{
  font-family:var(--font-sans);
  font-size:clamp(16px,1.02vw,17px);
  line-height:1.8;
  color:var(--body-text);
  background-color:var(--ink);
  background-image:
    radial-gradient(900px 620px at 84% -10%,rgba(56,225,230,.10),transparent 68%),
    radial-gradient(720px 520px at 6% 108%,rgba(255,122,26,.07),transparent 70%),
    linear-gradient(180deg,#08101D 0%,#070F1A 55%,#060C16 100%);
  background-attachment:fixed;
  padding-left:var(--rail);
  min-height:100vh;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
#main-content{display:block;min-height:52vh}

h1,h2,h3,h4{font-family:var(--font-serif);font-weight:700;color:var(--white);letter-spacing:.01em}
h1{font-size:clamp(42px,7.5vw,108px);line-height:1.05;font-weight:800}
h2{font-size:clamp(30px,4vw,56px);line-height:1.08}
h3{font-family:var(--font-sans);font-size:clamp(20px,1.9vw,26px);line-height:1.32;font-weight:700;letter-spacing:.02em}
h4{font-family:var(--font-sans);font-size:18px;line-height:1.4;font-weight:700}
p{max-width:70ch}
strong{color:var(--white);font-weight:700}
::selection{background:rgba(56,225,230,.32);color:var(--white)}
:focus-visible{outline:2px solid var(--cyan);outline-offset:3px;border-radius:2px}

.mono,.score{font-family:var(--font-mono);font-variant-numeric:tabular-nums}
.score{display:block;font-size:clamp(28px,4vw,56px);line-height:1;color:var(--white);letter-spacing:.02em}
.score--cyan{color:var(--cyan)}
.score--orange{color:var(--orange)}

.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}

/* ---------- 4. 容器与章节 ---------- */
.shell{width:100%;max-width:var(--shell);margin-inline:auto;padding-inline:clamp(20px,4vw,64px)}
.section{position:relative;padding-block:clamp(56px,7vw,120px)}
.section--tight{padding-block:clamp(32px,4vw,56px)}
.section--flush{padding-block:0}

.rule{height:1px;border:0;background:linear-gradient(90deg,rgba(56,225,230,.55),rgba(124,141,166,.16) 42%,rgba(124,141,166,0))}

.eyebrow{display:inline-flex;align-items:center;gap:10px;font-family:var(--font-mono);font-size:12px;letter-spacing:.24em;text-transform:uppercase;color:var(--cyan)}
.eyebrow::before{content:"";width:20px;height:1px;background:var(--cyan);display:block}

.tag-label{display:inline-block;font-family:var(--font-mono);font-size:11px;letter-spacing:.28em;text-transform:uppercase;color:var(--mist);border-top:1px solid rgba(124,141,166,.42);padding-top:8px}

.lede{font-size:clamp(17px,1.4vw,20px);line-height:1.85;color:#C9D7E8;max-width:56ch}
.note-col{font-size:13.5px;line-height:1.9;color:var(--mist);max-width:34ch}
.section-head{display:flex;flex-wrap:wrap;align-items:flex-end;justify-content:space-between;gap:20px 32px;margin-bottom:clamp(24px,3vw,44px)}

/* ---------- 5. 栅格与节奏 ---------- */
.grid{display:grid;gap:clamp(20px,2.4vw,36px)}
.grid--7-5{grid-template-columns:7fr 5fr}
.grid--8-4{grid-template-columns:8fr 4fr}
.grid--9-3{grid-template-columns:9fr 3fr}
.grid--2{grid-template-columns:repeat(2,minmax(0,1fr))}
.grid--3{grid-template-columns:repeat(3,minmax(0,1fr))}

.stack{display:flex;flex-direction:column;gap:18px}
.stack--sm{gap:10px}
.stack--lg{gap:28px}

/* ---------- 6. 面板 / 标签 / 状态 ---------- */
.panel{border:1px solid var(--line-soft);border-radius:4px;padding:clamp(20px,2.4vw,32px);background:var(--ink-2)}
.panel--glass{
  background:linear-gradient(158deg,rgba(22,38,61,.88),rgba(15,27,45,.62));
  border-color:rgba(56,225,230,.24);
  -webkit-backdrop-filter:blur(10px) saturate(1.1);
  backdrop-filter:blur(10px) saturate(1.1);
}
.panel--solid{background:#0A1424;border-color:rgba(124,141,166,.2)}

.chip{display:inline-flex;align-items:center;gap:6px;padding:5px 11px;border:1px solid rgba(124,141,166,.35);border-radius:2px;font-size:12.5px;letter-spacing:.06em;color:#C5D3E4;background:rgba(22,38,61,.5);line-height:1.5}
.chip--live{color:var(--green);border-color:rgba(61,220,151,.45)}
.chip--pending{color:var(--yellow);border-color:rgba(242,201,76,.45)}

.dot{display:inline-block;width:8px;height:8px;border-radius:50%;background:var(--mist);flex:none}
.dot--live{background:var(--green);box-shadow:0 0 0 3px rgba(61,220,151,.16)}
.dot--ok{background:var(--cyan);box-shadow:0 0 0 3px rgba(56,225,230,.16)}
.dot--warn{background:var(--yellow);box-shadow:0 0 0 3px rgba(242,201,76,.16)}

/* ---------- 7. 按钮 ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  padding:12px 20px;border-radius:3px;border:1px solid transparent;
  font-family:var(--font-sans);font-size:15px;font-weight:700;letter-spacing:.06em;line-height:1.3;
  transition:transform .22s ease,background-color .22s ease,color .22s ease,box-shadow .22s ease,border-color .22s ease;
}
.btn--signal{background:var(--orange);color:var(--black);box-shadow:0 12px 28px -16px rgba(255,122,26,.95)}
.btn--signal:hover{background:#FF9047;transform:translateY(-2px)}
.btn--cyan{background:var(--cyan);color:var(--black);box-shadow:0 12px 28px -18px rgba(56,225,230,.9)}
.btn--cyan:hover{background:#63EEF2;transform:translateY(-2px)}
.btn--ghost{border-color:rgba(56,225,230,.45);color:var(--white);background:rgba(56,225,230,.06)}
.btn--ghost:hover{background:rgba(56,225,230,.15);border-color:var(--cyan);transform:translateY(-2px)}

.copy-btn{font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;padding:4px 9px;border:1px solid rgba(124,141,166,.4);border-radius:2px;color:var(--mist);transition:color .2s,border-color .2s,background-color .2s}
.copy-btn:hover{color:var(--cyan);border-color:var(--cyan);background:rgba(56,225,230,.08)}
.copy-btn[data-copied="true"]{color:var(--green);border-color:rgba(61,220,151,.6);background:rgba(61,220,151,.08)}

/* ---------- 8. 面包屑与长文 ---------- */
.crumbs{display:flex;flex-wrap:wrap;align-items:center;gap:8px;font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;color:var(--mist)}
.crumbs li{display:inline-flex;align-items:center;gap:8px}
.crumbs li+li::before{content:"/";color:rgba(124,141,166,.5)}
.crumbs a{color:var(--mist);transition:color .2s}
.crumbs a:hover{color:var(--cyan)}
.crumbs [aria-current="page"]{color:var(--white)}

.prose{max-width:70ch}
.prose p+p{margin-top:1.05em}
.prose h2{margin-top:1.5em;margin-bottom:.5em}
.prose h3{margin-top:1.5em;margin-bottom:.4em}
.prose a{color:var(--cyan);text-decoration:underline;text-underline-offset:3px;text-decoration-thickness:1px}
.prose ul,.prose ol{margin-block:1em;display:grid;gap:.5em}
.prose ul li{position:relative;padding-left:20px}
.prose ul li::before{content:"";position:absolute;left:0;top:.78em;width:8px;height:1px;background:var(--cyan)}
.prose blockquote{border-left:2px solid var(--line-cyan);padding-left:18px;color:#C9D7E8}

/* ---------- 9. 媒体容器（页面阶段放置图片） ---------- */
.media{
  position:relative;display:block;overflow:hidden;border-radius:3px;
  border:1px solid rgba(124,141,166,.2);
  aspect-ratio:16/10;
  background:linear-gradient(152deg,#0D1A2C 0%,#16263D 46%,#0A1524 100%);
  isolation:isolate;
}
.media::after{
  content:"";position:absolute;inset:0;z-index:0;pointer-events:none;
  background:
    repeating-linear-gradient(114deg,rgba(56,225,230,.11) 0 1px,transparent 1px 26px),
    radial-gradient(62% 72% at 78% 6%,rgba(56,225,230,.22),transparent 66%),
    radial-gradient(52% 62% at 8% 100%,rgba(255,122,26,.14),transparent 72%);
}
.media__img{position:relative;z-index:1;width:100%;height:100%;object-fit:cover}
.media__tag{
  position:absolute;top:12px;left:12px;z-index:2;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.16em;
  padding:4px 8px;color:var(--cyan);background:rgba(8,16,29,.84);border:1px solid rgba(56,225,230,.42);
}
.media__caption{
  position:absolute;left:0;right:0;bottom:0;z-index:2;
  padding:16px;font-size:12.5px;letter-spacing:.04em;color:#D7E2F0;
  background:linear-gradient(0deg,rgba(5,10,18,.94),rgba(5,10,18,0));
}
.media--wide{aspect-ratio:21/9}
.media--tall{aspect-ratio:4/5}
.media--square{aspect-ratio:1/1}

/* ---------- 10. 跳至主内容 ---------- */
.skip-link{
  position:fixed;top:10px;left:calc(var(--rail) + 12px);z-index:200;
  padding:10px 18px;border-radius:2px;
  font-family:var(--font-sans);font-size:14px;font-weight:700;letter-spacing:.06em;
  color:var(--black);background:var(--cyan);
  transform:translateY(-180%);
  transition:transform .2s ease;
}
.skip-link:focus{transform:translateY(0)}

/* ---------- 11. 头部：转播导轨 ---------- */
.site-header{position:fixed;top:0;left:0;bottom:0;width:var(--rail);z-index:100}

.scroll-progress{
  position:fixed;top:0;left:calc(var(--rail) - 2px);width:2px;height:100vh;
  transform:scaleY(var(--p,0));transform-origin:top;
  background:linear-gradient(180deg,var(--cyan),rgba(56,225,230,.35) 55%,var(--orange));
  z-index:130;pointer-events:none;
}

.frame-rail{
  display:flex;flex-direction:column;height:100%;width:100%;
  background:linear-gradient(180deg,#0A1424 0%,#08101D 52%,#060D18 100%);
  border-right:1px solid rgba(56,225,230,.18);
  box-shadow:0 0 44px rgba(5,10,18,.9);
}

.frame-brand{display:flex;flex-direction:column;align-items:center;gap:12px;padding:16px 6px 14px;border-bottom:1px solid var(--line-soft);transition:background-color .2s}
.frame-brand:hover{background:rgba(56,225,230,.05)}
.frame-brand__mark{
  display:grid;place-items:center;width:38px;height:38px;border-radius:9px;
  border:1px solid rgba(56,225,230,.55);
  font-family:var(--font-mono);font-size:20px;line-height:1;color:var(--cyan);
  box-shadow:inset 0 0 18px rgba(56,225,230,.18),0 0 22px -10px rgba(56,225,230,.6);
}
.frame-brand__name{writing-mode:vertical-rl;font-family:var(--font-sans);font-size:13px;font-weight:700;letter-spacing:.22em;color:var(--white);line-height:1}
.frame-brand__tag{writing-mode:vertical-rl;font-size:10px;letter-spacing:.2em;color:var(--mist);line-height:1}

.nav-toggle{display:none;align-items:center;gap:10px;padding:9px 12px;border:1px solid rgba(56,225,230,.4);border-radius:2px;color:var(--white);font-family:var(--font-mono);font-size:12px;letter-spacing:.16em}
.nav-toggle__bars{display:grid;gap:4px;width:16px;flex:none}
.nav-toggle__bars i{display:block;height:1.5px;background:var(--cyan);transition:transform .25s ease}
.nav-toggle__text{font-size:12px;letter-spacing:.16em}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:first-child{transform:translateY(2.75px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:last-child{transform:translateY(-2.75px) rotate(-45deg)}

.site-nav{display:flex;flex-direction:column;flex:1;min-height:0;padding:14px 0 12px;overflow-y:auto;overscroll-behavior:contain;scrollbar-width:thin}
.site-nav__label{margin:0 0 10px;text-align:center;font-family:var(--font-mono);font-size:9px;letter-spacing:.28em;color:var(--mist);text-transform:uppercase;max-width:none}
.site-nav__list{display:flex;flex-direction:column}
.site-nav__item{border-top:1px solid rgba(124,141,166,.14)}
.site-nav__item:last-child{border-bottom:1px solid rgba(124,141,166,.14)}
.site-nav__link{position:relative;display:flex;flex-direction:column;align-items:center;gap:3px;padding:11px 4px;color:#B9C7D8;transition:color .2s,background-color .2s}
.site-nav__link::before{content:"";position:absolute;left:0;top:50%;width:3px;height:0;background:var(--cyan);transform:translateY(-50%);transition:height .28s ease}
.site-nav__link:hover{color:var(--white);background:rgba(56,225,230,.06)}
.site-nav__link:hover::before{height:58%}
.site-nav__num{font-family:var(--font-mono);font-size:10px;letter-spacing:.1em;color:var(--mist);transition:color .2s}
.site-nav__text{font-family:var(--font-sans);font-size:12px;font-weight:700;letter-spacing:.08em;white-space:nowrap}
.site-nav__link[aria-current="page"]{color:var(--white);background:rgba(56,225,230,.10)}
.site-nav__link[aria-current="page"]::before{height:100%;box-shadow:0 0 14px rgba(56,225,230,.7)}
.site-nav__link[aria-current="page"] .site-nav__num{color:var(--orange)}

.site-nav__cta{
  writing-mode:vertical-rl;margin-block:auto 6px;margin-inline:auto;
  padding:16px 9px;font-size:13px;letter-spacing:.14em;align-self:center;
}

.nav-scrim{display:none}

/* ---------- 12. 页脚：转播结束信息牌 ---------- */
.site-footer{
  position:relative;
  margin-top:clamp(56px,8vw,120px);
  padding-block:clamp(48px,6vw,88px) clamp(28px,3vw,40px);
  background:linear-gradient(180deg,#060D18 0%,#08101D 46%,#050A12 100%);
  border-top:1px solid rgba(124,141,166,.16);
}
.site-footer::before{
  content:"";position:absolute;top:0;left:0;right:0;height:2px;
  background:linear-gradient(90deg,var(--cyan),rgba(56,225,230,0) 46%,var(--orange));
}
.footer__shell{padding-inline:clamp(20px,4vw,64px)}

.footer__top{
  display:grid;grid-template-columns:minmax(0,1.05fr) minmax(0,1.6fr);
  gap:clamp(28px,4vw,64px);
  padding-bottom:clamp(28px,3.4vw,48px);
  border-bottom:1px solid rgba(124,141,166,.16);
}
.footer__brand{min-width:0}
.footer__wordmark{font-family:var(--font-serif);font-size:clamp(28px,3.4vw,44px);font-weight:800;line-height:1.1;letter-spacing:.04em;color:var(--white);max-width:none}
.footer__line{margin-top:10px;font-size:14px;letter-spacing:.08em;color:var(--mist);max-width:none}
.footer__status{display:flex;flex-wrap:wrap;gap:14px 18px;margin-top:20px}
.footer__status-item{display:inline-flex;align-items:center;gap:8px;font-family:var(--font-mono);font-size:11.5px;letter-spacing:.14em;color:#B9C7D8}

.footer__nav{min-width:0}
.footer__groups{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:clamp(18px,2.4vw,32px)}
.footer__group{min-width:0}
.footer__group-title{margin-bottom:14px;font-family:var(--font-mono);font-size:11px;font-weight:500;letter-spacing:.26em;color:var(--mist)}
.footer__links{display:grid;gap:10px}
.footer__link{position:relative;display:inline-block;font-size:14.5px;letter-spacing:.04em;color:#C5D3E4;transition:color .2s,transform .2s}
.footer__link::after{content:"";position:absolute;left:0;bottom:-2px;width:0;height:1px;background:var(--cyan);transition:width .24s ease}
.footer__link:hover{color:var(--cyan);transform:translateX(3px)}
.footer__link:hover::after{width:100%}

.footer__contact{
  display:grid;grid-template-columns:minmax(0,1.45fr) minmax(0,1fr);
  gap:clamp(20px,2.6vw,40px);
  margin-top:clamp(28px,3.4vw,44px);
}
.footer__contact-list{display:grid;gap:14px}
.footer__contact-item{display:flex;flex-wrap:wrap;align-items:baseline;gap:8px 14px}
.footer__contact-label{font-family:var(--font-mono);font-size:11px;letter-spacing:.22em;color:var(--mist);min-width:64px}
.footer__contact-value{font-size:15px;color:var(--white);letter-spacing:.02em;word-break:break-word}
.footer__contact-note{font-size:13px;line-height:1.9;color:var(--mist);max-width:44ch;border-left:1px solid rgba(56,225,230,.28);padding-left:16px}

.footer__bottom{
  display:flex;flex-wrap:wrap;align-items:center;gap:10px 24px;
  margin-top:clamp(24px,3vw,36px);padding-top:20px;
  border-top:1px solid rgba(124,141,166,.16);
  font-family:var(--font-mono);font-size:12px;letter-spacing:.08em;color:var(--mist);
}
.footer__copyright{max-width:none}
.footer__legal{max-width:none;color:#96A6BC}
.footer__meta{max-width:none;margin-left:auto;color:rgba(124,141,166,.9)}

/* ---------- 13. 返回顶部 ---------- */
.back-to-top{
  position:fixed;right:20px;bottom:20px;z-index:90;
  display:inline-flex;align-items:center;gap:8px;
  padding:10px 15px;border-radius:2px;
  border:1px solid rgba(56,225,230,.38);
  background:rgba(15,27,45,.86);
  -webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);
  font-family:var(--font-mono);font-size:12px;letter-spacing:.16em;color:var(--white);
  opacity:0;transform:translateY(12px);pointer-events:none;
  transition:opacity .3s ease,transform .3s ease,background-color .2s ease,border-color .2s ease;
}
.back-to-top::before{content:"↑";color:var(--cyan);font-size:13px;line-height:1}
.back-to-top.is-visible{opacity:1;transform:translateY(0);pointer-events:auto}
.back-to-top:hover{background:rgba(56,225,230,.16);border-color:var(--cyan)}

/* ---------- 14. 响应式 ---------- */
@media (max-width:1180px){
  .site-nav__text{font-size:11.5px;letter-spacing:.04em}
  .footer__top{grid-template-columns:1fr}
}

@media (max-width:900px){
  :root{--rail:0px}
  body{padding-left:0;padding-top:var(--bar)}

  .scroll-progress{left:0;right:0;top:0;width:auto;height:3px;transform:scaleX(var(--p,0));transform-origin:left}

  .site-header{top:0;left:0;right:0;bottom:auto;width:100%;height:var(--bar)}
  .frame-rail{
    flex-direction:row;align-items:center;gap:12px;height:var(--bar);
    padding:0 clamp(14px,4vw,24px);
    border-right:0;border-bottom:1px solid rgba(56,225,230,.2);
    box-shadow:0 14px 34px -22px rgba(5,10,18,.95);
  }
  .frame-brand{flex-direction:row;align-items:center;gap:10px;padding:0;border-bottom:0}
  .frame-brand:hover{background:none}
  .frame-brand__mark{width:32px;height:32px;border-radius:7px;font-size:17px}
  .frame-brand__name{writing-mode:horizontal-tb;font-size:15px;letter-spacing:.1em}
  .frame-brand__tag{display:none}

  .nav-toggle{display:inline-flex;margin-left:auto}

  .site-nav{
    position:fixed;top:var(--bar);left:0;bottom:0;
    width:min(340px,86vw);flex:none;
    padding:18px 0 24px;overflow-y:auto;
    background:linear-gradient(180deg,#0B1626,#08101D);
    border-right:1px solid rgba(56,225,230,.24);
    box-shadow:26px 0 64px rgba(5,10,18,.7);
    transform:translateX(-102%);
    transition:transform .32s cubic-bezier(.22,.7,.3,1);
    z-index:110;
  }
  .site-nav[data-open]{transform:translateX(0)}
  .site-nav__label{text-align:left;padding:0 22px;font-size:10px;letter-spacing:.3em}
  .site-nav__list{padding-bottom:8px}
  .site-nav__item{border-top:1px solid rgba(124,141,166,.14)}
  .site-nav__link{flex-direction:row;align-items:baseline;justify-content:flex-start;gap:14px;padding:15px 22px}
  .site-nav__link::before{top:0;left:0;width:3px;height:100%;transform:none;opacity:0;transition:opacity .2s}
  .site-nav__link:hover::before{height:100%;opacity:1}
  .site-nav__link[aria-current="page"]::before{opacity:1}
  .site-nav__text{font-size:15px;letter-spacing:.08em}
  .site-nav__cta{writing-mode:horizontal-tb;margin:18px 22px 0;padding:14px 18px;width:calc(100% - 44px);align-self:stretch}

  .nav-scrim{
    display:block;position:fixed;top:var(--bar);left:0;right:0;bottom:0;z-index:105;
    background:rgba(5,10,18,.74);
    -webkit-backdrop-filter:blur(2px);backdrop-filter:blur(2px);
  }
  .nav-scrim[hidden]{display:none}

  .skip-link{left:12px}

  .grid--7-5,.grid--8-4,.grid--9-3,.grid--2,.grid--3{grid-template-columns:1fr}

  .footer__contact{grid-template-columns:1fr}
  .footer__contact-note{border-left:0;padding-left:0;border-top:1px solid rgba(56,225,230,.24);padding-top:14px;max-width:60ch}
  .footer__bottom{font-size:11.5px}
  .footer__meta{margin-left:0;width:100%}

  .back-to-top{right:14px;bottom:14px;padding:9px 12px;font-size:11px}
}

@media (max-width:620px){
  .footer__groups{grid-template-columns:repeat(2,minmax(0,1fr))}
  .footer__wordmark{font-size:26px}
  .footer__contact-value{font-size:14px}
  .section{padding-block:clamp(44px,9vw,72px)}
}

@media (max-height:760px) and (min-width:901px){
  .frame-brand__tag{display:none}
}

/* ---------- 15. 降低动效偏好 ---------- */
@media (prefers-reduced-motion: reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{
    animation-duration:.001ms !important;
    animation-iteration-count:1 !important;
    transition-duration:.001ms !important;
  }
  .back-to-top{transform:none}
}