/* ============================================================
   /assets/site.css — 博业服务 共享外壳与基础组件
   分区：1 reset · 2 变量 · 3 基础排版 · 4 工具类 · 5 刊头
        6 导航 · 7 页脚 · 8 按钮 · 9 内容骨架 · 10 基础组件
        11 图片容器 · 12 动效 · 13 响应式 · 14 打印
   ============================================================ */

/* ---------- 1. reset ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body,h1,h2,h3,h4,h5,p,ul,ol,figure,dl,dd,blockquote{margin:0}
ul,ol{padding:0}
ul[class],ol[class]{list-style:none}
img,svg{display:block;max-width:100%}
a{color:inherit}
button{font:inherit;color:inherit;background:none;border:0}
table{border-collapse:collapse}

/* ---------- 2. 变量 ---------- */
:root{
  --by-indigo:#1B2A5B;
  --by-midnight:#0E1838;
  --by-amber:#D99932;
  --by-amber-light:#F3C977;
  --by-celadon:#4F8F7E;
  --by-celadon-light:#A8CBBF;
  --by-paper:#F7F4ED;
  --by-mist:#E6E2D8;
  --by-ink:#14161C;
  --by-brick:#B8543F;

  --by-line:rgba(20,22,28,.16);
  --by-line-strong:rgba(20,22,28,.42);
  --by-indigo-soft:rgba(27,42,91,.72);
  --by-shadow-card:8px 8px 0 rgba(27,42,91,.14);
  --by-shadow-btn:5px 5px 0 rgba(27,42,91,.2);

  --by-wrap:1180px;
  --by-gutter:clamp(18px,4vw,48px);
  --by-font-cn:"Noto Sans SC","Source Han Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif;
  --by-font-mono:"IBM Plex Mono","JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  --by-ease:cubic-bezier(.2,.7,.3,1);
  --by-radius:2px;
}

/* ---------- 3. 基础排版 ---------- */
body{
  background:var(--by-paper);
  color:var(--by-ink);
  font-family:var(--by-font-cn);
  font-size:clamp(15px,.35vw + 14px,17px);
  font-weight:400;
  line-height:1.75;
  letter-spacing:.01em;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
h1,h2,h3,h4{font-weight:900;line-height:1.18;letter-spacing:.01em;color:var(--by-indigo)}
strong,b{font-weight:800}
code,kbd,samp{font-family:var(--by-font-mono);font-size:.92em}
::selection{background:var(--by-amber-light);color:var(--by-midnight)}

:focus-visible{outline:3px solid var(--by-amber);outline-offset:3px;border-radius:1px}
.by-footer :focus-visible{outline-color:var(--by-amber-light)}

/* ---------- 4. 工具类 ---------- */
.by-wrap{
  width:100%;
  max-width:calc(var(--by-wrap) + var(--by-gutter) * 2);
  margin-inline:auto;
  padding-inline:var(--by-gutter);
}
.by-mono{font-family:var(--by-font-mono);letter-spacing:.05em;font-variant-numeric:tabular-nums}
.by-main{display:block}
#main-content{scroll-margin-top:24px}
.by-skip{
  position:absolute;left:12px;top:-80px;z-index:120;
  display:inline-block;padding:.7em 1.1em;
  background:var(--by-amber-light);color:var(--by-midnight);
  border:2px solid var(--by-midnight);font-weight:800;text-decoration:none;
  transition:top .2s var(--by-ease);
}
.by-skip:focus{top:12px}
.by-blueprint{position:relative;isolation:isolate}
.by-blueprint::before{
  content:"";position:absolute;inset:0;z-index:-1;pointer-events:none;
  background-image:
    repeating-linear-gradient(to right,rgba(27,42,91,.08) 0 1px,transparent 1px 72px),
    repeating-linear-gradient(to bottom,rgba(27,42,91,.06) 0 1px,transparent 1px 72px);
}

/* 顶部滚动进度 */
.by-progress{
  position:fixed;inset:0 0 auto 0;height:3px;z-index:70;
  background:rgba(27,42,91,.12);pointer-events:none;
}
.by-progress__bar{
  display:block;height:100%;width:100%;
  transform:scaleX(0);transform-origin:0 50%;
  background:linear-gradient(90deg,var(--by-amber),var(--by-celadon));
}

/* ---------- 5. 刊头 ---------- */
.by-header{
  position:relative;isolation:isolate;
  background:var(--by-paper);
  border-bottom:3px solid var(--by-indigo);
}
.by-header::before{
  content:"";position:absolute;inset:0;z-index:-1;pointer-events:none;
  background-image:
    repeating-linear-gradient(to right,rgba(27,42,91,.09) 0 1px,transparent 1px 64px),
    repeating-linear-gradient(to bottom,rgba(27,42,91,.06) 0 1px,transparent 1px 64px);
}
.by-masthead{padding-top:clamp(16px,2.6vw,30px)}
.by-masthead__inner{
  width:100%;max-width:calc(var(--by-wrap) + var(--by-gutter) * 2);
  margin-inline:auto;padding-inline:var(--by-gutter);
  display:grid;align-items:center;gap:10px 18px;
  grid-template-columns:1fr auto 1fr;
  grid-template-areas:"meta brand quick";
}
.by-masthead__meta{
  grid-area:meta;
  display:flex;flex-wrap:wrap;align-items:center;gap:.35em .6em;
  font-size:.68rem;letter-spacing:.16em;text-transform:uppercase;
  color:var(--by-indigo-soft);
}
.by-masthead__meta-sep{color:var(--by-amber);font-weight:800}
.by-masthead__brandwrap{
  grid-area:brand;justify-self:center;text-align:center;text-decoration:none;
  display:block;padding-bottom:.2em;
}
.by-masthead__brand{
  display:block;
  font-size:clamp(2rem,5.4vw,3.35rem);
  font-weight:900;line-height:1;letter-spacing:.06em;
  color:var(--by-indigo);
  text-shadow:4px 4px 0 rgba(217,153,50,.3);
  transition:text-shadow .25s var(--by-ease),color .25s var(--by-ease);
}
.by-masthead__brandwrap:hover .by-masthead__brand{text-shadow:4px 4px 0 var(--by-amber)}
.by-masthead__descriptor{
  display:block;margin-top:.7em;
  font-family:var(--by-font-mono);
  font-size:clamp(.58rem,1.3vw,.72rem);
  letter-spacing:.34em;text-transform:uppercase;
  color:var(--by-indigo-soft);
}
.by-masthead__quick{grid-area:quick;justify-self:end}
.by-quick{
  display:inline-flex;flex-direction:column;gap:2px;
  padding:.55em .95em;text-decoration:none;
  border:2px solid var(--by-indigo);background:var(--by-amber-light);color:var(--by-midnight);
  box-shadow:4px 4px 0 rgba(27,42,91,.22);
  transition:transform .22s var(--by-ease),box-shadow .22s var(--by-ease),background .22s;
}
.by-quick:hover{transform:translate(-2px,-2px);box-shadow:6px 6px 0 rgba(27,42,91,.3);background:var(--by-amber)}
.by-quick__label{
  font-family:var(--by-font-mono);font-size:.6rem;letter-spacing:.2em;
  text-transform:uppercase;color:rgba(14,24,56,.7);
}
.by-quick__text{font-size:.86rem;font-weight:800;line-height:1.3}

/* ---------- 6. 导航 ---------- */
.by-nav{
  width:100%;max-width:calc(var(--by-wrap) + var(--by-gutter) * 2);
  margin-inline:auto;margin-top:clamp(14px,2.2vw,24px);
  padding-inline:var(--by-gutter);
  border-top:2px solid var(--by-midnight);
}
.by-nav__list{
  display:flex;flex-wrap:wrap;justify-content:center;align-items:stretch;
  margin:0;padding:0;list-style:none;
}
.by-nav__item{border-right:1px solid var(--by-line)}
.by-nav__item:first-child{border-left:1px solid var(--by-line)}
.by-nav__link{
  display:inline-flex;align-items:baseline;gap:.5em;
  padding:.85em clamp(.7em,1.7vw,1.4em);
  text-decoration:none;color:var(--by-indigo);
  font-weight:800;font-size:.95rem;letter-spacing:.03em;
  transition:background .2s var(--by-ease),color .2s var(--by-ease),box-shadow .2s var(--by-ease);
}
.by-nav__index{
  font-family:var(--by-font-mono);font-size:.62rem;letter-spacing:.1em;
  color:rgba(27,42,91,.55);transition:color .2s var(--by-ease);
}
.by-nav__label{white-space:nowrap}
.by-nav__link:hover{background:var(--by-amber-light)}
.by-nav__link:hover .by-nav__index{color:var(--by-indigo)}
.by-nav__link[aria-current="page"]{
  background:var(--by-indigo);color:var(--by-paper);
  box-shadow:inset 0 -3px 0 var(--by-amber);
}
.by-nav__link[aria-current="page"] .by-nav__index{color:var(--by-amber-light)}

.by-navtoggle{
  grid-area:toggle;justify-self:end;
  display:none;align-items:center;gap:.6em;
  padding:.55em .8em;
  border:2px solid var(--by-indigo);background:var(--by-paper);color:var(--by-indigo);
  font-weight:800;font-size:.84rem;letter-spacing:.08em;
  box-shadow:3px 3px 0 rgba(27,42,91,.22);cursor:pointer;
  transition:background .2s var(--by-ease),color .2s var(--by-ease),box-shadow .2s var(--by-ease);
}
.by-navtoggle__bars{display:grid;gap:3px;width:18px}
.by-navtoggle__bars span{
  display:block;height:2px;background:currentColor;
  transition:transform .25s var(--by-ease),opacity .2s var(--by-ease);
}
.by-navtoggle__text{font-weight:800}
.by-navtoggle[aria-expanded="true"]{
  background:var(--by-indigo);color:var(--by-paper);
  box-shadow:3px 3px 0 var(--by-amber);
}
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bars span:nth-child(1){transform:translateY(5px) rotate(45deg)}
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bars span:nth-child(2){opacity:0}
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bars span:nth-child(3){transform:translateY(-5px) rotate(-45deg)}

/* ---------- 7. 页脚 ---------- */
.by-footer{
  position:relative;isolation:isolate;
  margin-top:clamp(48px,7vw,96px);
  background:var(--by-midnight);color:var(--by-paper);
  border-top:4px solid var(--by-amber);
}
.by-footer::before{
  content:"";position:absolute;inset:0;z-index:-1;pointer-events:none;
  background-image:
    repeating-linear-gradient(to right,rgba(168,203,191,.14) 0 1px,transparent 1px 64px),
    repeating-linear-gradient(to bottom,rgba(168,203,191,.1) 0 1px,transparent 1px 64px);
}
.by-footer__top{padding-block:clamp(34px,5vw,64px)}
.by-footer__grid{
  display:grid;gap:clamp(24px,4vw,44px);
  grid-template-columns:repeat(auto-fit,minmax(236px,1fr));
  align-items:start;
}
.by-footer__brandcol{min-width:0}
.by-footer__brand{
  font-size:clamp(1.55rem,3.4vw,2.25rem);font-weight:900;line-height:1.1;
  letter-spacing:.06em;color:var(--by-paper);margin-bottom:.4em;
}
.by-footer__tagline{
  margin:0 0 1em;font-weight:800;font-size:.95rem;
  color:var(--by-amber-light);letter-spacing:.06em;
}
.by-footer__note{
  margin:0;max-width:34ch;font-size:.85rem;line-height:1.85;
  color:rgba(247,244,237,.72);
}
.by-footer__col{min-width:0}
.by-footer__title{
  margin:0 0 1em;padding-bottom:.6em;
  font-family:var(--by-font-mono);font-size:.7rem;font-weight:700;
  letter-spacing:.22em;text-transform:uppercase;
  color:var(--by-celadon-light);
  border-bottom:1px solid rgba(247,244,237,.22);
}
.by-footer__list{display:grid;gap:.5em;list-style:none;margin:0;padding:0}
.by-footer__link{
  display:inline-block;font-size:.92rem;text-decoration:none;
  color:rgba(247,244,237,.9);
  border-bottom:1px solid transparent;
  transition:color .2s var(--by-ease),border-color .2s var(--by-ease);
}
.by-footer__link:hover{color:var(--by-amber-light);border-color:currentColor}
.by-footer__kv{
  display:flex;gap:.75em;margin:0 0 .8em;
  font-size:.86rem;line-height:1.7;color:rgba(247,244,237,.9);
}
.by-footer__k{
  flex:none;min-width:3.1em;padding-top:.2em;
  font-family:var(--by-font-mono);font-size:.66rem;letter-spacing:.14em;
  text-transform:uppercase;color:var(--by-celadon-light);
}
.by-footer__v{min-width:0;word-break:break-word}
.by-footer__col .by-btn{margin-top:.6em}
.by-footer__bottom{
  padding-block:1.1em 1.4em;
  background:rgba(14,24,56,.62);
  border-top:1px solid rgba(247,244,237,.18);
}
.by-footer__bottominner{
  display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;
  gap:.7em 1.6em;
  font-size:.76rem;color:rgba(247,244,237,.7);
}
.by-footer__copy,.by-footer__icp{margin:0}
.by-footer__legal{display:flex;flex-wrap:wrap;gap:.4em 1.2em;list-style:none;margin:0;padding:0}
.by-footer__legal a{
  color:inherit;text-decoration:none;
  border-bottom:1px solid rgba(247,244,237,.35);
  transition:color .2s var(--by-ease),border-color .2s var(--by-ease);
}
.by-footer__legal a:hover{color:var(--by-amber-light);border-color:currentColor}

/* ---------- 8. 按钮 ---------- */
.by-btn{
  display:inline-flex;align-items:center;justify-content:center;gap:.55em;
  padding:.75em 1.25em;border:2px solid var(--by-indigo);border-radius:var(--by-radius);
  background:var(--by-paper);color:var(--by-indigo);
  font-weight:800;font-size:.9rem;letter-spacing:.04em;line-height:1.3;
  text-decoration:none;cursor:pointer;
  box-shadow:var(--by-shadow-btn);
  transition:transform .22s var(--by-ease),box-shadow .22s var(--by-ease),
             background .22s var(--by-ease),color .22s var(--by-ease),border-color .22s var(--by-ease);
}
.by-btn:hover{transform:translate(-2px,-2px);box-shadow:7px 7px 0 rgba(27,42,91,.28);background:var(--by-amber-light)}
.by-btn:active{transform:translate(2px,2px);box-shadow:none}
.by-btn--solid{background:var(--by-indigo);color:var(--by-paper);border-color:var(--by-midnight)}
.by-btn--solid:hover{background:var(--by-indigo);color:var(--by-amber-light);box-shadow:7px 7px 0 var(--by-amber)}
.by-btn--amber{background:var(--by-amber);color:var(--by-midnight);border-color:var(--by-amber-light);box-shadow:4px 4px 0 rgba(0,0,0,.34)}
.by-btn--amber:hover{background:var(--by-amber-light);box-shadow:6px 6px 0 rgba(0,0,0,.42)}
.by-btn--sm{padding:.5em .9em;font-size:.8rem;box-shadow:3px 3px 0 rgba(27,42,91,.2)}
.by-btn--sm:hover{box-shadow:5px 5px 0 rgba(27,42,91,.28)}

/* ---------- 9. 内容骨架 ---------- */
.by-section{padding-block:clamp(36px,5.5vw,84px)}
.by-section__head{max-width:72ch;margin-bottom:clamp(20px,3vw,36px)}
.by-eyebrow{
  display:inline-flex;align-items:center;gap:.7em;
  font-family:var(--by-font-mono);font-size:.7rem;font-weight:700;
  letter-spacing:.24em;text-transform:uppercase;color:var(--by-celadon);
}
.by-eyebrow::before{content:"";width:28px;height:2px;background:currentColor;flex:none}
.by-section__title{
  margin:.45em 0 .35em;
  font-size:clamp(1.55rem,3.6vw,2.5rem);font-weight:900;
  color:var(--by-indigo);
}
.by-lede{font-size:clamp(.98rem,1.5vw,1.08rem);line-height:1.85;color:rgba(20,22,28,.78);max-width:62ch}

.by-grid{display:grid;gap:clamp(16px,2.4vw,28px)}
.by-grid--2{grid-template-columns:repeat(auto-fit,minmax(260px,1fr))}
.by-grid--3{grid-template-columns:repeat(auto-fit,minmax(216px,1fr))}
.by-grid--4{grid-template-columns:repeat(auto-fit,minmax(176px,1fr))}
.by-split{display:grid;gap:clamp(20px,3vw,40px);grid-template-columns:minmax(0,1fr)}

.by-crumbs{margin:0 0 clamp(16px,2.4vw,26px)}
.by-crumbs ol{display:flex;flex-wrap:wrap;align-items:center;gap:.3em 0;list-style:none;margin:0;padding:0}
.by-crumbs li{
  display:inline-flex;align-items:center;
  font-family:var(--by-font-mono);font-size:.72rem;letter-spacing:.08em;
  color:var(--by-indigo-soft);
}
.by-crumbs li + li::before{content:"/";margin-inline:.7em;color:var(--by-amber);font-weight:700}
.by-crumbs a{color:var(--by-indigo);text-decoration:none;border-bottom:1px solid rgba(27,42,91,.35)}
.by-crumbs a:hover{color:var(--by-brick);border-color:currentColor}
.by-crumbs [aria-current="page"]{color:var(--by-ink);font-weight:700}

.by-note{
  padding:clamp(14px,2vw,20px) clamp(16px,2.2vw,24px);
  border:2px solid var(--by-indigo);border-left-width:6px;
  background:var(--by-mist);color:var(--by-ink);
  font-size:.92rem;line-height:1.8;
}

/* ---------- 10. 基础组件 ---------- */
.by-card{
  position:relative;min-width:0;
  padding:clamp(18px,2.4vw,30px);
  border:2px solid var(--by-indigo);border-radius:var(--by-radius);
  background:var(--by-paper);
  box-shadow:var(--by-shadow-card);
}
.by-card__head{
  display:flex;flex-wrap:wrap;align-items:baseline;justify-content:space-between;
  gap:.4em 1em;margin-bottom:.9em;padding-bottom:.7em;
  border-bottom:2px solid rgba(27,42,91,.18);
}
.by-card__index{
  font-family:var(--by-font-mono);font-size:.7rem;font-weight:700;
  letter-spacing:.16em;text-transform:uppercase;color:var(--by-amber);
}
.by-card__title{font-size:clamp(1.05rem,1.8vw,1.3rem);font-weight:900;color:var(--by-indigo);line-height:1.3}

.by-tag{
  display:inline-flex;align-items:center;gap:.4em;
  padding:.2em .6em;border:1px solid var(--by-indigo);border-radius:var(--by-radius);
  background:var(--by-mist);color:var(--by-indigo);
  font-family:var(--by-font-mono);font-size:.68rem;font-weight:700;
  letter-spacing:.1em;text-transform:uppercase;white-space:nowrap;
}
.by-tag--amber{background:var(--by-amber-light);border-color:var(--by-amber);color:var(--by-midnight)}
.by-tag--celadon{background:var(--by-celadon-light);border-color:var(--by-celadon);color:var(--by-midnight)}

.by-badge{
  display:inline-flex;align-items:center;gap:.45em;
  font-family:var(--by-font-mono);font-size:.7rem;font-weight:700;
  letter-spacing:.1em;text-transform:uppercase;color:var(--by-celadon);
}
.by-badge::before{
  content:"";width:7px;height:7px;flex:none;border-radius:50%;
  background:currentColor;box-shadow:0 0 0 3px rgba(79,143,126,.18);
}
.by-badge--amber{color:#9a6a11}
.by-badge--amber::before{box-shadow:0 0 0 3px rgba(217,153,50,.22)}
.by-badge--brick{color:var(--by-brick)}
.by-badge--brick::before{box-shadow:0 0 0 3px rgba(184,84,63,.2)}

.by-kv{display:grid;gap:0;margin:0}
.by-kv > div{
  display:grid;grid-template-columns:minmax(92px,32%) minmax(0,1fr);
  gap:.7em;padding:.6em 0;
  border-top:1px dashed var(--by-line);
}
.by-kv > div:last-child{border-bottom:1px dashed var(--by-line)}
.by-kv dt{
  font-family:var(--by-font-mono);font-size:.7rem;font-weight:700;
  letter-spacing:.12em;text-transform:uppercase;
  color:var(--by-indigo-soft);padding-top:.25em;
}
.by-kv dd{margin:0;font-weight:600;line-height:1.7}

.by-table-wrap{
  border:2px solid var(--by-indigo);border-radius:var(--by-radius);
  background:var(--by-paper);overflow-x:auto;
  box-shadow:6px 6px 0 rgba(27,42,91,.12);
}
.by-table{width:100%;min-width:560px;font-size:.9rem}
.by-table caption{
  caption-side:top;text-align:left;padding:.9em 1em 0;
  font-family:var(--by-font-mono);font-size:.7rem;letter-spacing:.14em;
  text-transform:uppercase;color:var(--by-indigo-soft);
}
.by-table th,.by-table td{padding:.75em 1em;text-align:left;vertical-align:top;border-bottom:1px solid var(--by-line)}
.by-table thead th{
  background:var(--by-indigo);color:var(--by-paper);
  font-family:var(--by-font-mono);font-size:.72rem;font-weight:700;
  letter-spacing:.12em;text-transform:uppercase;white-space:nowrap;
  border-bottom:0;
}
.by-table tbody tr:nth-child(even){background:var(--by-mist)}
.by-table tbody tr:hover{background:var(--by-amber-light)}
.by-table tbody tr:last-child td{border-bottom:0}
.by-table td:first-child{font-weight:700;color:var(--by-indigo)}
.by-table .by-mono{font-size:.86rem}

.by-acc{
  border:2px solid var(--by-indigo);border-radius:var(--by-radius);
  background:var(--by-paper);box-shadow:6px 6px 0 rgba(27,42,91,.12);
  overflow:hidden;
}
.by-acc__item + .by-acc__item{border-top:2px solid var(--by-indigo)}
.by-acc__trigger{
  width:100%;display:flex;align-items:center;justify-content:space-between;gap:1em;
  padding:.95em 1.1em;text-align:left;cursor:pointer;
  font-weight:800;font-size:.96rem;color:var(--by-indigo);
  transition:background .2s var(--by-ease),color .2s var(--by-ease);
}
.by-acc__trigger:hover{background:var(--by-mist)}
.by-acc__trigger[aria-expanded="true"]{background:var(--by-amber-light)}
.by-acc__icon{
  flex:none;width:1.5em;height:1.5em;display:grid;place-items:center;
  border:1px solid currentColor;border-radius:var(--by-radius);
  font-family:var(--by-font-mono);font-size:1rem;line-height:1;
}
.by-acc__icon::before{content:"+"}
.by-acc__trigger[aria-expanded="true"] .by-acc__icon::before{content:"–"}
.by-acc__panel{
  padding:0 1.1em 1.1em;
  border-top:1px dashed var(--by-line);
  font-size:.93rem;line-height:1.85;color:rgba(20,22,28,.82);
}
.by-acc__panel[hidden]{display:none}

/* ---------- 11. 图片容器 ---------- */
.by-figure{
  margin:0;min-width:0;
  border:2px solid var(--by-indigo);border-radius:var(--by-radius);
  background:var(--by-mist);
  box-shadow:var(--by-shadow-card);
  overflow:hidden;
}
.by-figure__frame{
  position:relative;display:grid;place-items:center;
  aspect-ratio:var(--by-ratio,16/9);
  background-color:var(--by-mist);
  background-image:
    repeating-linear-gradient(45deg,rgba(27,42,91,.09) 0 2px,transparent 2px 12px),
    repeating-linear-gradient(to bottom,rgba(27,42,91,.05) 0 1px,transparent 1px 36px);
  overflow:hidden;
}
.by-figure__frame > img{width:100%;height:100%;object-fit:cover}
.by-figure__caption{
  padding:.6em .9em;border-top:2px solid var(--by-indigo);
  background:var(--by-paper);
  font-family:var(--by-font-mono);font-size:.72rem;letter-spacing:.06em;
  color:var(--by-indigo-soft);
}
.by-figure--wide{--by-ratio:21/9}
.by-figure--tall{--by-ratio:3/4}
.by-figure--square{--by-ratio:1/1}

/* ---------- 12. 动效 ---------- */
.by-js [data-reveal]{
  opacity:0;transform:translateY(14px);
  transition:opacity .38s var(--by-ease),transform .38s var(--by-ease);
  will-change:opacity,transform;
}
.by-js [data-reveal].is-in{opacity:1;transform:none}

/* ---------- 13. 响应式 ---------- */
@media (min-width:900px){
  .by-split{grid-template-columns:minmax(200px,3fr) minmax(0,9fr)}
  .by-split--even{grid-template-columns:minmax(0,4fr) minmax(0,8fr)}
}
@media (max-width:1040px){
  .by-nav__link{padding:.8em .9em;font-size:.9rem}
  .by-nav__index{font-size:.58rem}
}
@media (max-width:860px){
  .by-masthead__inner{
    grid-template-columns:1fr auto 1fr;
    grid-template-areas:"meta brand toggle" "quick quick quick";
    row-gap:12px;
  }
  .by-masthead__meta{flex-direction:column;align-items:flex-start;gap:.15em;font-size:.6rem}
  .by-masthead__quick{grid-area:quick;justify-self:stretch}
  .by-quick{width:100%;flex-direction:row;align-items:center;justify-content:space-between;gap:1em}
  .by-navtoggle{display:inline-flex}
  .by-nav{display:none;border-top:2px solid var(--by-midnight);background:var(--by-paper)}
  .by-nav[data-open]{display:block}
  .by-nav__list{flex-direction:column;align-items:stretch}
  .by-nav__item{border-right:0;border-left:0;border-bottom:1px solid var(--by-line)}
  .by-nav__item:first-child{border-left:0;border-top:1px solid var(--by-line)}
  .by-nav__link{display:flex;width:100%;justify-content:space-between;padding:.95em 1.1em;font-size:1rem}
  .by-nav__link[aria-current="page"]{box-shadow:inset 4px 0 0 var(--by-amber)}
  .by-acc__trigger{font-size:.92rem}
}
@media (max-width:640px){
  .by-table-wrap{overflow:visible;border:0;background:none;box-shadow:none}
  .by-table{min-width:0;font-size:.9rem}
  .by-table caption{padding:0 0 .8em}
  .by-table thead{display:none}
  .by-table tbody tr{
    display:block;margin-bottom:14px;
    border:2px solid var(--by-indigo);border-radius:var(--by-radius);
    background:var(--by-paper);box-shadow:5px 5px 0 rgba(27,42,91,.12);
  }
  .by-table tbody tr:nth-child(even){background:var(--by-paper)}
  .by-table tbody tr:hover{background:var(--by-paper)}
  .by-table td{
    display:grid;grid-template-columns:minmax(80px,38%) minmax(0,1fr);
    gap:.7em;padding:.65em .9em;border-bottom:1px dashed var(--by-line);
  }
  .by-table td:last-child{border-bottom:0}
  .by-table td::before{
    content:attr(data-label);
    font-family:var(--by-font-mono);font-size:.68rem;font-weight:700;
    letter-spacing:.1em;text-transform:uppercase;color:var(--by-indigo-soft);
  }
  .by-kv > div{grid-template-columns:minmax(0,1fr);gap:.15em}
  .by-footer__bottominner{justify-content:flex-start}
}
@media (max-width:560px){
  .by-masthead__meta{display:none}
  .by-masthead__descriptor{letter-spacing:.22em}
  .by-footer__kv{flex-direction:column;gap:.1em}
  .by-footer__k{min-width:0;padding-top:0}
}
@media (hover:none){
  .by-btn:hover,.by-quick:hover{transform:none}
}

/* ---------- 14. 打印 ---------- */
@media print{
  .by-progress,.by-navtoggle,.by-skip{display:none!important}
  .by-header,.by-footer{background:#fff!important;color:#000!important;border-color:#000!important}
  .by-footer__brand,.by-footer__link,.by-footer__note,.by-footer__tagline{color:#000!important}
  .by-js [data-reveal]{opacity:1!important;transform:none!important}
}

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