*,*::before,*::after{box-sizing:border-box}
:root{
  --ink:#000;
  --paper:#fff;
  --soft:#f1f1f1;
  --line:#dedede;
  --rail:240px;
  --edge:clamp(18px,4vw,64px);
}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;
  overflow-x:hidden;
  background:var(--paper);
  color:var(--ink);
  font-family:"Atkinson Hyperlegible",-apple-system,BlinkMacSystemFont,"Segoe UI","Noto Sans SC","PingFang SC","Microsoft YaHei",sans-serif;
  font-size:18px;
  line-height:1.6;
}
a{color:var(--ink)}
:focus-visible{outline:3px solid var(--ink);outline-offset:3px}

/* ---------- 左侧竖排导航 ---------- */
.rail{
  position:fixed;
  inset:0 auto 0 0;
  z-index:30;
  width:var(--rail);
  display:flex;
  flex-direction:column;
  gap:18px;
  padding:26px 20px 22px;
  background:var(--paper);
  border-right:2px solid var(--ink);
  overflow-y:auto;
}
.brand{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:8px;
  padding:6px 0;
  min-height:44px;
  text-decoration:none;
  font-size:1.4rem;
  font-weight:700;
  line-height:1.02;
  letter-spacing:-0.045em;
}
.brand-logo{display:block;width:36px;height:36px;object-fit:contain}
.brand-txt{display:block}
.menu-btn{display:none}

.rail-nav{display:flex;flex-direction:column;gap:2px}
.grp{position:relative}
.grp-btn{
  width:100%;
  min-height:44px;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:8px;
  padding:10px 0;
  font:inherit;
  font-weight:700;
  letter-spacing:0.06em;
  color:var(--ink);
  background:none;
  border:0;
  border-bottom:1px solid var(--line);
  cursor:pointer;
  text-align:left;
}
.grp-x{font-weight:400;transition:transform .18s ease}
.grp.open .grp-x,.grp:hover .grp-x{transform:rotate(45deg)}
.grp ul{list-style:none;margin:0;padding:0 0 6px;display:none}
.grp:hover ul,.grp:focus-within ul,.grp.open ul{display:block}
.grp a{
  display:block;
  padding:11px 0 11px 12px;
  min-height:44px;
  text-decoration:none;
  font-size:0.98rem;
  line-height:1.45;
  border-left:2px solid transparent;
}
.grp a:hover,.grp a:focus-visible{border-left-color:var(--ink);font-weight:700}

.rail-contact{
  margin-top:auto;
  display:flex;
  flex-direction:column;
  gap:2px;
  padding-top:18px;
  border-top:2px solid var(--ink);
}
.rail-contact small{
  display:block;
  font-size:0.72rem;
  letter-spacing:0.22em;
  font-weight:700;
}
.rail-contact .host{
  font-size:0.82rem;
  line-height:1.4;
  word-break:break-all;
  color:#333;
}
.rail-contact a{
  display:flex;
  align-items:center;
  min-height:44px;
  font-weight:700;
  text-decoration:none;
  text-decoration-thickness:2px;
  text-underline-offset:4px;
}
.rail-contact a:hover{text-decoration:underline}

/* ---------- 主体 ---------- */
main{
  margin-left:var(--rail);
  display:grid;
  grid-template-columns:minmax(190px,250px) minmax(0,1fr);
  gap:clamp(20px,3vw,52px);
  align-items:start;
  padding:clamp(24px,4vw,56px) var(--edge) 0;
}
article{min-width:0}

/* 侧栏目录 */
.toc{
  position:sticky;
  top:28px;
  padding:20px 18px 16px;
  border:2px solid var(--ink);
  border-bottom-width:5px;
  border-radius:28px;
  background:var(--paper);
}
.toc small{
  display:block;
  font-size:0.72rem;
  font-weight:700;
  letter-spacing:0.22em;
}
.toc h2{
  margin:4px 0 10px;
  font-size:1.15rem;
  font-weight:700;
  letter-spacing:-0.02em;
  line-height:1.2;
}
.toc ol{list-style:none;margin:0;padding:0}
.toc li a{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:8px 0;
  font-size:0.95rem;
  text-decoration:none;
  border-bottom:1px solid var(--line);
}
.toc li:last-child a{border-bottom:0}
.toc li a:hover{font-weight:700;text-decoration:underline;text-underline-offset:4px}

/* ---------- Hero ---------- */
.hero{
  position:relative;
  display:grid;
  grid-template-columns:minmax(0,1fr) minmax(0,0.8fr);
  align-items:end;
  gap:clamp(16px,3vw,40px);
  min-height:45vh;
  padding:clamp(18px,4vw,40px) 0 clamp(26px,5vw,48px);
  border-bottom:2px solid var(--ink);
  overflow:hidden;
}
.hero-ghost{
  position:absolute;
  top:-0.16em;
  right:-0.06em;
  z-index:0;
  font-size:clamp(4rem,16vw,14rem);
  font-weight:700;
  line-height:0.8;
  letter-spacing:-0.05em;
  color:transparent;
  -webkit-text-stroke:2px var(--ink);
  opacity:0.14;
  white-space:nowrap;
  pointer-events:none;
}
.hero-txt{position:relative;z-index:2;align-self:end}
.hero h1{
  margin:0;
  font-size:clamp(2.6rem,7vw,6rem);
  font-weight:700;
  line-height:0.94;
  letter-spacing:-0.05em;
}
.hero-lead{
  margin:16px 0 0;
  max-width:32ch;
  font-size:1rem;
  line-height:1.55;
}
.hero-art{position:relative;z-index:1}
.hero-art img{
  display:block;
  width:100%;
  height:auto;
  border-radius:28px;
  border-bottom:4px solid var(--ink);
  filter:grayscale(1) contrast(1.04);
  will-change:transform;
}

/* ---------- 正文 ---------- */
article > section{
  padding:clamp(34px,6vw,82px) 0;
  border-bottom:1px solid var(--ink);
  scroll-margin-top:76px;
}
article > section:last-child{border-bottom:0;padding-bottom:clamp(20px,4vw,40px)}
article h2{
  margin:0 0 20px;
  font-size:clamp(1.9rem,5vw,3.4rem);
  font-weight:700;
  line-height:1.02;
  letter-spacing:-0.045em;
  max-width:22ch;
}
article h3{
  margin:34px 0 12px;
  font-size:clamp(1.2rem,2.4vw,1.6rem);
  font-weight:700;
  line-height:1.25;
  letter-spacing:-0.02em;
}
article small{
  display:block;
  margin-bottom:10px;
  font-size:0.74rem;
  font-weight:700;
  letter-spacing:0.22em;
  color:#333;
}
article p{margin:0 0 1.05em;max-width:64ch}
article li{margin:0 0 0.4em}
article ul,article ol{max-width:64ch;padding-left:1.25em;margin:0 0 1.1em}
article figure{margin:26px 0}
article img{max-width:100%;height:auto;border-radius:28px}
article blockquote{
  margin:26px 0;
  padding:6px 0 6px 20px;
  border-left:5px solid var(--ink);
  font-size:1.1rem;
  font-weight:700;
  line-height:1.5;
  max-width:58ch;
}
article strong{font-weight:700}
article a{text-decoration:underline;text-decoration-thickness:2px;text-underline-offset:4px}
article hr{border:0;border-top:2px solid var(--ink);margin:34px 0}
article table{width:100%;border-collapse:collapse;margin:22px 0;font-size:0.98rem}
article th,article td{border-bottom:1px solid var(--line);padding:10px 6px;text-align:left}

/* ---------- 页脚 ---------- */
.foot{
  margin-left:var(--rail);
  margin-top:clamp(28px,6vw,72px);
  padding:26px var(--edge) 44px;
  border-top:2px solid var(--ink);
  display:flex;
  flex-wrap:wrap;
  align-items:flex-start;
  justify-content:space-between;
  gap:18px 40px;
}
.copy{margin:0;font-weight:700;font-size:0.95rem;padding:11px 0}
.foot-nav{display:flex;flex-wrap:wrap;gap:14px clamp(18px,3vw,48px)}
.foot-nav dl{margin:0;display:flex;flex-direction:column}
.foot-nav dt,.foot-nav dd{margin:0}
.foot-nav a{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:8px 0;
  font-size:0.95rem;
  text-decoration:none;
}
.foot-nav dt a{font-weight:700}
.foot-nav a:hover{text-decoration:underline;text-decoration-thickness:2px;text-underline-offset:4px}
.to-top{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:8px 0;
  font-size:0.95rem;
  font-weight:700;
  text-decoration:none;
}
.to-top:hover{text-decoration:underline;text-underline-offset:4px}

/* ---------- 动效 ---------- */
@media (prefers-reduced-motion:no-preference){
  article > section{
    animation:rise 0.5s ease both;
  }
  article > section:nth-child(3){animation-delay:.04s}
  article > section:nth-child(4){animation-delay:.08s}
  article > section:nth-child(5){animation-delay:.12s}
  article > section:nth-child(6){animation-delay:.16s}
  article > section:nth-child(7){animation-delay:.2s}
  article > section:nth-child(8){animation-delay:.24s}
  .toc li{animation:slide 0.4s ease both}
  .toc li:nth-child(2){animation-delay:.04s}
  .toc li:nth-child(3){animation-delay:.08s}
  .toc li:nth-child(4){animation-delay:.12s}
  .toc li:nth-child(5){animation-delay:.16s}
  .toc li:nth-child(6){animation-delay:.2s}
  .toc li:nth-child(7){animation-delay:.24s}
  @keyframes rise{from{opacity:0;transform:translateY(18px)}to{opacity:1;transform:none}}
  @keyframes slide{from{opacity:0;transform:translateX(-8px)}to{opacity:1;transform:none}}
}

/* ---------- 窄屏 ---------- */
@media (max-width:960px){
  .rail{
    position:static;
    inset:auto;
    width:auto;
    flex-direction:row;
    flex-wrap:wrap;
    align-items:center;
    gap:10px 14px;
    padding:14px var(--edge);
    border-right:0;
    border-bottom:2px solid var(--ink);
    overflow:visible;
  }
  .brand{flex:1 1 60%;font-size:1.5rem}
  .menu-btn{
    display:inline-flex;
    align-items:center;
    justify-content:center;
    min-height:44px;
    padding:10px 20px;
    margin-left:auto;
    font:inherit;
    font-size:0.95rem;
    font-weight:700;
    color:var(--paper);
    background:var(--ink);
    border:2px solid var(--ink);
    border-radius:999px;
    cursor:pointer;
  }
  .rail-nav{display:none;flex:1 0 100%;flex-direction:column;gap:2px;padding-bottom:6px}
  .rail.open .rail-nav{display:flex}
  .grp ul{display:none}
  .rail.open .grp ul{display:block}
  .grp a{padding-left:14px}
  .rail-contact{display:none}
  .rail.open .rail-contact{display:flex;flex:1 0 100%;margin-top:6px;padding-top:14px}

  main{
    display:flex;
    flex-direction:column;
    gap:28px;
    margin-left:0;
    padding-top:22px;
  }
  article{order:1}
  .toc{order:2;position:static;border-radius:24px}
  .foot{margin-left:0}
  .hero{
    grid-template-columns:1fr;
    min-height:0;
    padding-top:16px;
  }
  .hero-ghost{top:-0.1em;opacity:0.12}
  .hero-art{order:2}
  article > section{scroll-margin-top:16px}
}

@media (max-width:420px){
  body{font-size:17px}
  .brand{font-size:1.3rem}
  .foot{flex-direction:column;gap:10px}
  .to-top{padding-bottom:0}
}

button[aria-expanded]{min-width:44px;min-height:44px}