/* =========================================================
   聚合入口 · 共享样式表  /assets/site.css
   展览画册式布局 + 报文刊头 + 入口线路语言
   ========================================================= */

/* ---------- 1. 设计变量 ---------- */
:root{
  --ink:#1B2A4A;
  --ink-deep:#12203A;
  --signal:#FF6B35;
  --cyan:#00E5CC;
  --paper:#F4F1EA;
  --paper-2:#E8E4DA;
  --mist:#D8DCE3;
  --slate:#5A6478;
  --wine:#B23A48;
  --teal:#1E6E63;
  --warn:#FFD9C7;

  --rule:2px;
  --wrap:1200px;
  --gap:clamp(16px,2.2vw,32px);
  --space-section:clamp(56px,8vw,116px);
  --ease:cubic-bezier(.2,.7,.2,1);

  --font-sans:"Noto Sans SC","Source Han Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,-apple-system,sans-serif;
  --font-serif:"Noto Serif SC","Source Han Serif SC","Songti SC",Georgia,"Times New Roman",serif;
  --font-mono:"JetBrains Mono","SFMono-Regular",Menlo,Consolas,"Liberation Mono","Courier New",monospace;
}

/* ---------- 2. 重置 ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,h5,p,figure,ul,ol,dl,dd,blockquote,pre{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}
main{display:block}
hr{border:0}

/* ---------- 3. 中文排版基调 ---------- */
body{
  font-family:var(--font-sans);
  font-size:17px;
  line-height:1.75;
  letter-spacing:.01em;
  color:var(--ink);
  background:var(--paper);
  overflow-x:hidden;
}
h1,h2,h3,h4{font-weight:900;letter-spacing:-.01em;line-height:1.22}
h1{font-size:clamp(40px,7vw,96px);line-height:1.04}
h2{font-size:clamp(28px,3.4vw,44px)}
h3{font-size:20px;line-height:1.45}
h4{font-size:17px;line-height:1.5}
p{max-width:76ch}
a{color:var(--ink);text-decoration-color:var(--signal);text-underline-offset:3px}
::selection{background:var(--cyan);color:var(--ink-deep)}
:focus-visible{outline:3px solid var(--signal);outline-offset:3px}
.btn:focus-visible,.nav-toggle:focus-visible,.copy-btn:focus-visible,.back-to-top:focus-visible{outline-color:var(--cyan)}

/* ---------- 4. 工具 ---------- */
.wrap{width:min(100% - 2.5rem,var(--wrap));margin-inline:auto}
.wrap--narrow{width:min(100% - 2.5rem,760px);margin-inline:auto}
.mono{font-family:var(--font-mono);font-variant-numeric:tabular-nums;letter-spacing:.05em}
.label{
  display:block;font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;
  text-transform:uppercase;color:var(--slate);
}
.lede{font-family:var(--font-serif);font-weight:600;font-size:clamp(18px,2vw,22px);line-height:1.72;color:var(--ink)}
.visually-hidden{position:absolute;width:1px;height:1px;margin:-1px;padding:0;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}
.divider{height:1px;background:linear-gradient(90deg,transparent,var(--cyan) 14%,var(--cyan) 86%,transparent);opacity:.7;margin-block:clamp(24px,4vw,44px)}
.path-line{position:relative;height:2px;background:var(--mist);margin-block:clamp(22px,3.4vw,42px)}
.path-line::after{content:"";position:absolute;left:0;top:-3px;width:8px;height:8px;border-radius:50%;background:var(--cyan);box-shadow:0 0 0 3px rgba(0,229,204,.24)}
.note{border-left:4px solid var(--signal);background:var(--paper-2);padding:14px 18px;font-size:15px;line-height:1.75;color:var(--slate);max-width:60ch}

/* ---------- 5. 色彩分区（展览画册） ---------- */
.band{position:relative;padding-block:var(--space-section)}
.band--paper{background:var(--paper);color:var(--ink)}
.band--mist{background:var(--paper-2);color:var(--ink)}
.band--ink{background:var(--ink);color:var(--paper)}
.band--deep{background:var(--ink-deep);color:var(--paper)}
.band--teal{background:var(--teal);color:var(--paper)}
.band--wine{background:var(--wine);color:var(--paper)}
.band--ink .label,.band--deep .label,.band--teal .label,.band--wine .label{color:rgba(244,241,234,.72)}
.band--ink .lede,.band--deep .lede,.band--teal .lede,.band--wine .lede{color:var(--paper)}
.band--ink .note,.band--deep .note,.band--teal .note,.band--wine .note{background:rgba(244,241,234,.08);color:rgba(244,241,234,.84)}
.band--ink .path-line,.band--deep .path-line{background:rgba(216,220,227,.28)}
.band--ink a,.band--deep a,.band--teal a,.band--wine a{color:var(--cyan)}

/* ---------- 6. 章节封面 ---------- */
.section-head{
  display:grid;grid-template-columns:minmax(0,7fr) minmax(0,4fr);
  gap:var(--gap);align-items:end;margin-bottom:clamp(24px,4vw,48px);
  padding-bottom:16px;border-bottom:2px solid currentColor;
}
.section-head__title{margin:0}
.section-head__meta{
  margin:0;justify-self:end;text-align:right;
  font-family:var(--font-mono);font-size:13px;letter-spacing:.08em;
  color:var(--slate);line-height:1.7;
}
.band--ink .section-head__meta,.band--deep .section-head__meta,
.band--teal .section-head__meta,.band--wine .section-head__meta{color:rgba(244,241,234,.7)}
.chapter-no{
  display:inline-block;font-family:var(--font-mono);font-size:13px;
  letter-spacing:.14em;color:var(--signal);margin-bottom:10px;
}

/* ---------- 7. 按钮 ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:.5em;
  font-family:var(--font-sans);font-size:15px;font-weight:700;line-height:1;
  letter-spacing:.02em;padding:.85em 1.2em;border:2px solid transparent;border-radius:2px;
  text-decoration:none;white-space:nowrap;cursor:pointer;
  transition:transform .2s var(--ease),box-shadow .2s var(--ease),
             background-color .2s var(--ease),color .2s var(--ease),border-color .2s var(--ease);
}
.btn--signal{background:var(--signal);color:var(--ink-deep);border-color:var(--ink-deep);box-shadow:4px 4px 0 0 rgba(0,0,0,.5)}
.btn--signal:hover{background:#FF7F4F;transform:translate(-2px,-2px);box-shadow:6px 6px 0 0 rgba(0,0,0,.5)}
.btn--signal:active{transform:translate(2px,2px);box-shadow:1px 1px 0 0 rgba(0,0,0,.5)}
.btn--cyan{background:transparent;color:var(--cyan);border-color:var(--cyan);box-shadow:4px 4px 0 0 rgba(0,229,204,.24)}
.btn--cyan:hover{background:var(--cyan);color:var(--ink-deep);transform:translate(-2px,-2px);box-shadow:6px 6px 0 0 rgba(0,229,204,.24)}
.btn--cyan:active{transform:translate(2px,2px);box-shadow:1px 1px 0 0 rgba(0,229,204,.24)}
.btn--outline{background:var(--paper);color:var(--ink);border-color:var(--ink);box-shadow:4px 4px 0 0 var(--ink)}
.btn--outline:hover{transform:translate(-2px,-2px);box-shadow:6px 6px 0 0 var(--ink)}
.btn--outline:active{transform:translate(2px,2px);box-shadow:1px 1px 0 0 var(--ink)}
.btn--sm{padding:.65em .95em;font-size:13.5px}
.btn--block{width:100%}

/* ---------- 8. 展项卡片 ---------- */
.card{
  position:relative;display:flex;flex-direction:column;gap:12px;
  background:var(--paper);color:var(--ink);
  border:2px solid var(--ink);border-radius:2px;
  padding:clamp(18px,2.2vw,28px);
  box-shadow:6px 6px 0 0 var(--ink);
  transition:transform .25s var(--ease),box-shadow .25s var(--ease);
}
.card:hover{transform:translate(-3px,-3px);box-shadow:9px 9px 0 0 var(--ink)}
.card__label{font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;text-transform:uppercase;color:var(--slate)}
.card__title{font-size:20px;font-weight:900;line-height:1.35}
.card__body{font-size:15.5px;line-height:1.72;color:var(--slate)}
.card__foot{margin-top:auto;padding-top:12px;border-top:1px solid var(--mist);font-size:14px;font-family:var(--font-mono);letter-spacing:.04em;color:var(--slate)}
.card--ink{background:var(--ink);color:var(--paper);border-color:var(--paper);box-shadow:6px 6px 0 0 rgba(0,229,204,.45)}
.card--ink .card__body{color:rgba(244,241,234,.8)}
.card--ink .card__label{color:var(--cyan)}
.card--ink .card__foot{border-top-color:rgba(244,241,234,.22);color:rgba(244,241,234,.72)}
.card--teal{background:var(--teal);color:var(--paper);border-color:var(--ink-deep);box-shadow:6px 6px 0 0 rgba(0,229,204,.4)}
.card--teal .card__body{color:rgba(244,241,234,.86)}
.card--teal .card__label{color:var(--cyan)}
.card--teal .card__foot{border-top-color:rgba(244,241,234,.24);color:rgba(244,241,234,.78)}
.card--wine{background:var(--wine);color:var(--paper);border-color:var(--ink-deep);box-shadow:6px 6px 0 0 rgba(255,107,53,.45)}
.card--wine .card__body{color:rgba(244,241,234,.88)}
.card--wine .card__label{color:var(--warn)}
.card--wine .card__foot{border-top-color:rgba(244,241,234,.24);color:rgba(244,241,234,.8)}

/* ---------- 9. 标签 ---------- */
.tag{
  display:inline-flex;align-items:center;gap:6px;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.1em;text-transform:uppercase;
  padding:4px 9px;border:2px solid var(--ink);border-radius:2px;
  background:var(--paper);color:var(--ink);
}
.tag--signal{background:var(--signal);color:var(--ink-deep);border-color:var(--ink-deep)}
.tag--cyan{background:var(--cyan);color:var(--ink-deep);border-color:var(--ink-deep)}
.tag--wine{background:var(--wine);color:var(--paper);border-color:var(--ink-deep)}
.tag--teal{background:var(--teal);color:var(--paper);border-color:var(--ink-deep)}

/* ---------- 10. 网格 ---------- */
.grid{display:grid;gap:var(--gap)}
.grid--12{grid-template-columns:repeat(12,minmax(0,1fr))}
.grid--cards{display:grid;gap:var(--gap);grid-template-columns:repeat(auto-fit,minmax(258px,1fr))}
.col-main{grid-column:1 / span 7;min-width:0}
.col-aside{grid-column:10 / span 3;min-width:0}
.col-half{grid-column:span 6;min-width:0}
.col-full{grid-column:1 / -1;min-width:0}

/* ---------- 11. 图例 / 坐标索引 ---------- */
.legend{
  display:flex;flex-wrap:wrap;gap:10px 24px;
  padding:14px 18px;border:2px solid var(--ink);background:var(--paper-2);
}
.legend__item{display:flex;align-items:center;gap:8px;font-family:var(--font-mono);font-size:13px;letter-spacing:.06em;color:var(--slate)}
.legend__key{width:14px;height:14px;border:2px solid var(--ink);background:var(--paper);display:inline-block;flex:0 0 auto}
.legend__key--signal{background:var(--signal)}
.legend__key--cyan{background:var(--cyan)}
.legend__key--wine{background:var(--wine)}
.legend__key--teal{background:var(--teal)}
.coord{display:grid;gap:1px;background:var(--mist);border:2px solid var(--ink)}
.coord__item{display:grid;grid-template-columns:auto 1fr;gap:10px;background:var(--paper);padding:10px 14px;font-family:var(--font-mono);font-size:13px;letter-spacing:.04em;color:var(--slate)}
.coord__num{color:var(--signal)}

/* ---------- 12. 折叠面板 ---------- */
.fold{border:2px solid var(--ink);background:var(--paper);box-shadow:4px 4px 0 0 var(--ink)}
.fold + .fold{margin-top:14px}
.fold__sum{
  display:flex;align-items:center;justify-content:space-between;gap:14px;
  padding:16px 18px;font-size:17px;font-weight:700;cursor:pointer;list-style:none;
}
.fold__sum::-webkit-details-marker{display:none}
.fold__sum::after{content:"+";font-family:var(--font-mono);font-size:20px;line-height:1;color:var(--signal)}
.fold[open] .fold__sum{background:var(--paper-2);border-bottom:2px solid var(--ink)}
.fold[open] .fold__sum::after{content:"–"}
.fold__body{padding:16px 18px;font-size:15.5px;line-height:1.78;color:var(--slate)}
.fold__body p{max-width:70ch}

/* ---------- 13. 面包屑 ---------- */
.breadcrumb{padding-block:14px;border-bottom:1px solid var(--mist)}
.breadcrumb__list{display:flex;flex-wrap:wrap;align-items:center;gap:8px;font-family:var(--font-mono);font-size:13px;letter-spacing:.06em}
.breadcrumb__item{display:flex;align-items:center;gap:8px;color:var(--slate)}
.breadcrumb__item + .breadcrumb__item::before{content:"/";color:var(--cyan)}
.breadcrumb__link{color:var(--slate);text-decoration:none;border-bottom:1px solid transparent;transition:color .2s var(--ease),border-color .2s var(--ease)}
.breadcrumb__link:hover{color:var(--ink);border-bottom-color:var(--signal)}
.breadcrumb__item[aria-current="page"]{color:var(--ink);font-weight:700}

/* ---------- 14. 侧栏索引 ---------- */
.toc{border:2px solid var(--ink);background:var(--paper-2);padding:18px}
.toc__title{font-family:var(--font-mono);font-size:12px;letter-spacing:.14em;text-transform:uppercase;color:var(--signal)}
.toc__list{display:grid;gap:2px;margin-top:12px}
.toc__link{
  display:flex;align-items:baseline;gap:10px;padding:9px 10px;
  font-size:14.5px;color:var(--slate);text-decoration:none;
  border-left:3px solid transparent;transition:background-color .2s var(--ease),color .2s var(--ease),border-color .2s var(--ease);
}
.toc__link:hover{background:var(--paper);color:var(--ink)}
.toc__link.is-active{background:var(--paper);color:var(--ink);border-left-color:var(--cyan);font-weight:700}
.toc__link .mono{color:var(--signal)}

/* ---------- 15. 图片容器（供页面阶段复用） ---------- */
.figure{margin:0;display:grid;gap:10px}
.figure__frame{
  position:relative;overflow:hidden;border:2px solid var(--ink);
  background:var(--ink-deep);box-shadow:6px 6px 0 0 var(--ink);
}
.figure__frame::after{
  content:"";position:absolute;inset:0;pointer-events:none;
  background:linear-gradient(135deg,rgba(0,229,204,.18),transparent 58%);
}
.figure__media{display:block;width:100%;height:auto;aspect-ratio:16 / 9;object-fit:cover;background:var(--ink-deep)}
.figure--wide .figure__media{aspect-ratio:21 / 9}
.figure--square .figure__media{aspect-ratio:1 / 1}
.figure--tall .figure__media{aspect-ratio:3 / 4}
.figure__cap{font-family:var(--font-mono);font-size:13.5px;letter-spacing:.04em;color:var(--slate);line-height:1.7}
.band--ink .figure__cap,.band--deep .figure__cap,.band--teal .figure__cap,.band--wine .figure__cap{color:rgba(244,241,234,.74)}
.band--ink .figure__frame,.band--deep .figure__frame{border-color:var(--paper);box-shadow:6px 6px 0 0 rgba(0,229,204,.4)}

/* ---------- 16. 长文 ---------- */
.prose{max-width:72ch}
.prose > * + *{margin-top:1.1em}
.prose h2{font-size:clamp(24px,2.6vw,32px);margin-top:1.6em}
.prose h3{margin-top:1.4em}
.prose ul,.prose ol{padding-left:1.4em}
.prose ul{list-style:disc}
.prose ol{list-style:decimal}
.prose li{margin-bottom:.4em}
.prose a{text-decoration:underline;text-decoration-thickness:2px;text-decoration-color:var(--signal)}
.prose a:hover{color:var(--signal)}
.prose blockquote{border-left:4px solid var(--cyan);padding-left:18px;color:var(--slate)}

/* ---------- 17. 报头 ---------- */
.skip-link{
  position:absolute;left:50%;top:-70px;transform:translateX(-50%);z-index:99;
  background:var(--cyan);color:var(--ink-deep);font-size:14px;font-weight:700;
  padding:10px 18px;border:2px solid var(--ink-deep);text-decoration:none;
  transition:top .2s var(--ease);
}
.skip-link:focus{top:8px}
.site-header{
  position:sticky;top:0;z-index:80;
  background:var(--ink);color:var(--paper);
  border-bottom:2px solid var(--ink-deep);
}
.readout{position:absolute;left:0;right:0;bottom:-2px;height:3px;background:rgba(216,220,227,.16)}
.readout__bar{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--cyan),var(--signal))}
.masthead{border-bottom:1px solid rgba(216,220,227,.16);background:var(--ink)}
.masthead__inner{
  width:min(100% - 2rem,var(--wrap));margin-inline:auto;
  display:grid;grid-template-columns:1fr auto 1fr;align-items:center;
  gap:14px;min-height:66px;padding:12px 0;
}
.masthead__note{
  margin:0;display:flex;align-items:center;gap:8px;max-width:none;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;text-transform:uppercase;
  color:rgba(244,241,234,.68);
}
.masthead__note::before{content:"";width:8px;height:8px;border-radius:50%;background:var(--cyan);box-shadow:0 0 0 3px rgba(0,229,204,.2);flex:0 0 auto}
.brand{display:flex;align-items:center;gap:10px;justify-self:center;color:inherit;text-decoration:none}
.brand__mark{position:relative;display:block;width:30px;height:30px;border:2px solid var(--cyan);flex:0 0 auto}
.brand__mark::before{content:"";position:absolute;left:50%;top:50%;width:10px;height:10px;transform:translate(-50%,-50%);background:var(--signal)}
.brand__text{display:flex;flex-direction:column;line-height:1.12}
.brand__name{font-size:clamp(20px,2.4vw,26px);font-weight:900;letter-spacing:.08em}
.brand__tag{font-family:var(--font-mono);font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--cyan);margin-top:3px}
.masthead__actions{justify-self:end;display:flex;align-items:center;gap:10px}
.nav-toggle{
  display:none;align-items:center;gap:9px;
  font-family:var(--font-mono);font-size:13px;font-weight:700;letter-spacing:.1em;
  color:var(--paper);border:2px solid var(--cyan);border-radius:2px;
  padding:9px 13px;cursor:pointer;
}
.nav-toggle__bars{position:relative;display:block;width:16px;height:10px;flex:0 0 auto}
.nav-toggle__bars::before,.nav-toggle__bars::after{
  content:"";position:absolute;left:0;right:0;height:2px;background:var(--cyan);
  transition:transform .25s var(--ease),top .25s var(--ease);
}
.nav-toggle__bars::before{top:0}
.nav-toggle__bars::after{top:8px}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars::before{top:4px;transform:rotate(45deg)}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars::after{top:4px;transform:rotate(-45deg)}
.site-nav{position:relative;background:var(--ink-deep)}
.site-nav__list{
  width:min(100% - 2rem,var(--wrap));margin-inline:auto;
  display:flex;justify-content:center;align-items:stretch;
}
.site-nav__link{
  display:inline-flex;align-items:baseline;gap:8px;
  padding:13px 18px;font-size:15px;font-weight:500;color:rgba(244,241,234,.78);
  text-decoration:none;border-bottom:3px solid transparent;
  transition:color .2s var(--ease),background-color .2s var(--ease),border-color .2s var(--ease);
}
.site-nav__link:hover{color:#fff;background:rgba(0,229,204,.1)}
.site-nav__link:focus-visible{outline-offset:-4px}
.site-nav__link[aria-current="page"]{
  color:#fff;border-bottom-color:var(--signal);
  background:linear-gradient(180deg,rgba(255,107,53,0),rgba(255,107,53,.2));
}
.site-nav__index{font-family:var(--font-mono);font-size:11px;letter-spacing:.12em;color:var(--cyan)}
.site-nav__link[aria-current="page"] .site-nav__index{color:var(--signal)}

/* ---------- 18. 页脚 ---------- */
.site-footer{position:relative;background:var(--ink-deep);color:var(--paper);border-top:2px solid var(--ink)}
.footer-track{
  position:relative;height:2px;
  background:linear-gradient(90deg,transparent,var(--cyan) 15%,rgba(0,229,204,.25) 50%,var(--signal) 85%,transparent);
  opacity:.7;
}
.footer-track__dot{position:absolute;top:50%;width:10px;height:10px;margin-top:-5px;border-radius:50%;background:var(--ink-deep);border:2px solid var(--cyan)}
.footer-track__dot:nth-of-type(1){left:15%}
.footer-track__dot:nth-of-type(2){left:50%;border-color:var(--signal)}
.footer-track__dot:nth-of-type(3){left:85%}
.site-footer__inner{
  display:grid;grid-template-columns:minmax(0,1fr) minmax(0,2fr) minmax(0,1.1fr);
  gap:clamp(24px,3vw,48px);padding-block:clamp(40px,6vw,72px);
}
.site-footer__brand{min-width:0}
.brand--footer{justify-self:start;color:var(--paper)}
.site-footer__line{
  margin-top:16px;max-width:34ch;font-family:var(--font-serif);font-weight:600;
  font-size:17px;line-height:1.72;color:rgba(244,241,234,.84);
}
.site-footer__meta{margin-top:12px;font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;color:var(--cyan)}
.footer-nav{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:clamp(16px,2vw,32px)}
.footer-nav__title{
  font-family:var(--font-mono);font-size:13px;font-weight:700;letter-spacing:.14em;
  text-transform:uppercase;color:var(--signal);margin-bottom:12px;
}
.footer-nav__list{display:grid;gap:9px}
.footer-nav__list a{
  display:inline-block;font-size:15px;color:rgba(244,241,234,.82);text-decoration:none;
  border-bottom:1px solid transparent;transition:color .2s var(--ease),border-color .2s var(--ease);
}
.footer-nav__list a:hover{color:#fff;border-bottom-color:var(--cyan)}
.footer-contact__list{display:grid;gap:14px}
.contact-item{display:grid;grid-template-columns:minmax(0,1fr) auto;align-items:center;gap:6px 10px}
.contact-item > .label{grid-column:1 / -1;color:rgba(0,229,204,.86);font-size:11.5px}
.contact-item__value{font-size:14px;color:rgba(244,241,234,.9);overflow-wrap:anywhere;line-height:1.6}
.copy-btn{
  font-family:var(--font-mono);font-size:11.5px;letter-spacing:.1em;
  padding:5px 9px;color:var(--cyan);background:transparent;
  border:2px solid rgba(0,229,204,.5);border-radius:2px;cursor:pointer;
  transition:background-color .2s var(--ease),color .2s var(--ease),border-color .2s var(--ease);
}
.copy-btn:hover{background:var(--cyan);color:var(--ink-deep);border-color:var(--cyan)}
.copy-btn[data-copied="true"]{background:var(--signal);border-color:var(--signal);color:var(--ink-deep)}
.site-footer__base{
  border-top:1px solid rgba(216,220,227,.16);
  padding-block:20px 30px;display:grid;gap:8px;
}
.site-footer__legal{margin:0;max-width:none;font-family:var(--font-mono);font-size:13px;letter-spacing:.04em;color:rgba(244,241,234,.66)}
.site-footer__note{margin:0;max-width:80ch;font-size:13px;line-height:1.7;color:rgba(244,241,234,.56)}
.back-to-top{
  position:fixed;right:clamp(14px,2vw,28px);bottom:clamp(14px,2vw,28px);z-index:70;
  width:46px;height:46px;display:grid;place-items:center;
  font-family:var(--font-mono);font-size:17px;
  background:var(--signal);color:var(--ink-deep);
  border:2px solid var(--ink-deep);border-radius:2px;
  box-shadow:4px 4px 0 0 rgba(18,32,58,.55);cursor:pointer;
  opacity:0;visibility:hidden;transform:translateY(8px);
  transition:opacity .25s var(--ease),transform .25s var(--ease),visibility .25s var(--ease);
}
.back-to-top[data-visible="true"]{opacity:1;visibility:visible;transform:none}

/* ---------- 19. 显现动画 ---------- */
html.js [data-reveal]{opacity:0;transform:translateY(14px);transition:opacity .5s var(--ease),transform .5s var(--ease)}
html.js [data-reveal].is-in{opacity:1;transform:none}

/* ---------- 20. 响应式 ---------- */
@media (max-width:1080px){
  .col-main{grid-column:1 / -1}
  .col-aside{grid-column:1 / -1}
  .col-half{grid-column:1 / -1}
  .site-footer__inner{grid-template-columns:minmax(0,1fr) minmax(0,1fr)}
  .footer-contact{grid-column:1 / -1}
}
@media (max-width:900px){
  .masthead__inner{
    grid-template-columns:minmax(0,1fr) auto;
    grid-template-areas:"brand toggle" "actions actions";
    row-gap:10px;padding:10px 0;min-height:0;
  }
  .masthead__note{display:none}
  .brand{grid-area:brand;justify-self:start}
  .masthead__actions{grid-area:actions;justify-self:stretch;display:grid;grid-template-columns:1fr 1fr;gap:8px}
  .nav-toggle{grid-area:toggle;display:inline-flex}
  .site-header[data-condensed] .masthead__actions{display:none}
  .site-nav{
    position:absolute;left:0;right:0;top:100%;
    max-height:0;overflow:hidden;visibility:hidden;
    border-bottom:2px solid var(--ink);
    box-shadow:0 20px 0 -12px rgba(0,0,0,.35);
    transition:max-height .32s var(--ease),visibility .32s var(--ease);
  }
  .site-nav[data-open]{max-height:min(74vh,560px);overflow-y:auto;visibility:visible}
  .site-nav__list{flex-direction:column;width:100%;padding:8px 0 14px}
  .site-nav__link{
    width:100%;padding:14px 20px;font-size:16px;
    border-bottom:1px solid rgba(216,220,227,.14);border-left:3px solid transparent;
  }
  .site-nav__link[aria-current="page"]{
    border-bottom-color:rgba(216,220,227,.14);
    border-left-color:var(--signal);
    background:rgba(255,107,53,.14);
  }
  .section-head{grid-template-columns:1fr}
  .section-head__meta{justify-self:start;text-align:left}
}
@media (max-width:760px){
  body{font-size:16.5px}
  .wrap,.wrap--narrow{width:min(100% - 2rem,var(--wrap))}
  .site-footer__inner{grid-template-columns:1fr}
  .footer-nav{grid-template-columns:repeat(2,minmax(0,1fr))}
  .figure__frame,.card,.fold,.toc,.legend,.coord{box-shadow:4px 4px 0 0 var(--ink)}
  .band--ink .figure__frame,.band--deep .figure__frame{box-shadow:4px 4px 0 0 rgba(0,229,204,.4)}
  .masthead__actions{grid-template-columns:1fr}
  .btn{width:auto}
  .masthead__actions .btn{width:100%}
}
@media (max-width:430px){
  .footer-nav{grid-template-columns:1fr}
  .brand__tag{font-size:10px;letter-spacing:.1em}
}

/* ---------- 21. 动效降级 ---------- */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  html.js [data-reveal]{opacity:1;transform:none}
  *,*::before,*::after{
    animation-duration:.01ms !important;
    animation-iteration-count:1 !important;
    transition-duration:.01ms !important;
  }
}