:root{
  --ink:#1f1f1f;
  --paper:#ffffff;
  --grey:#f5f5f5;
  --line:#e3e3e3;
  --mute:#5d5d5d;
  --e1:0 1px 2px rgba(0,0,0,.06),0 2px 8px rgba(0,0,0,.05);
  --e2:0 4px 12px rgba(0,0,0,.07),0 12px 28px rgba(0,0,0,.06);
  --e3:0 10px 22px rgba(0,0,0,.09),0 24px 52px rgba(0,0,0,.08);
  --e4:0 16px 34px rgba(0,0,0,.12),0 40px 80px rgba(0,0,0,.10);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:Roboto,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,-apple-system,sans-serif;
  font-size:17px;
  line-height:1.72;
  font-weight:400;
  overflow-x:hidden;
}
a{color:var(--ink)}
img{max-width:100%}

/* ---------- 顶部：品牌居中，菜单分列两侧 ---------- */
.top{
  position:sticky;
  top:0;
  z-index:80;
  background:rgba(255,255,255,.88);
  -webkit-backdrop-filter:blur(16px) saturate(1.4);
  backdrop-filter:blur(16px) saturate(1.4);
  border-bottom:1px solid var(--line);
  box-shadow:var(--e1);
}
.topnav{
  display:flex;
  align-items:center;
  gap:.2rem;
  max-width:1320px;
  margin:0 auto;
  padding:.35rem .8rem;
  flex-wrap:wrap;
}
.topnav .side{
  display:flex;
  flex-wrap:wrap;
  gap:.1rem;
  margin:0;
  padding:0;
  list-style:none;
  flex:1 1 0;
  min-width:0;
}
.topnav .side.left{justify-content:flex-end}
.topnav .side.right{justify-content:flex-start}
.topnav .lnk{
  display:inline-flex;
  align-items:center;
  min-height:44px;
  padding:.25rem .5rem;
  font-size:1rem;
  text-decoration:none;
  white-space:nowrap;
  transition:background .18s ease,color .18s ease;
}
.topnav .lnk::before{
  content:"";
  width:6px;height:6px;
  border-radius:50%;
  background:currentColor;
  opacity:.4;
  margin-right:.42rem;
  flex:0 0 auto;
}
.topnav .lnk.on,.topnav .lnk:hover{background:var(--ink);color:#fff}
.topnav .lnk.on::before,.topnav .lnk:hover::before{opacity:.85}
.brand{
  order:1;
  display:inline-flex;
  align-items:center;
  gap:.4rem;
  min-height:44px;
  padding:.25rem .9rem;
  font-weight:700;
  font-size:1.02rem;
  letter-spacing:-.01em;
  text-decoration:none;
  box-shadow:var(--e2);
  background:var(--paper);
  z-index:2;
}
.topnav .side.left{order:0}
.topnav .side.right{order:2}
.brand-mark{font-size:1.05rem;line-height:1}

/* ---------- 首屏：左图右文 ---------- */
.hero{
  position:relative;
  display:grid;
  grid-template-columns:minmax(0,.92fr) minmax(0,1.08fr);
  gap:1.6rem;
  align-items:center;
  min-height:45vh;
  max-width:1320px;
  margin:0 auto;
  padding:1.6rem 1rem 1.2rem;
}
.hero::before{
  content:"";
  position:absolute;
  inset:0;
  background-image:radial-gradient(rgba(31,31,31,.16) 1px,transparent 1px);
  background-size:18px 18px;
  -webkit-mask-image:linear-gradient(to right,transparent 8%,#000 46%);
  mask-image:linear-gradient(to right,transparent 8%,#000 46%);
  pointer-events:none;
  z-index:0;
}
.hero > *{position:relative;z-index:1}
.hero-frame{
  position:relative;
  aspect-ratio:4/3;
  background:var(--grey);
  border:1px solid var(--line);
  box-shadow:var(--e3);
  transform:translateZ(0);
}
.hero-frame::after{
  content:"";
  position:absolute;
  inset:16px -14px -14px 16px;
  background:var(--grey);
  border:1px solid var(--line);
  z-index:-1;
}
.hero-stack{position:absolute;inset:0;overflow:hidden}
.hero-layer{margin:0;position:absolute;inset:0}
.hero-layer img{width:100%;height:100%;object-fit:cover;display:block}
.hero-stack .hero-layer{opacity:1}
.hero-stack.rot .hero-layer{opacity:0;transition:opacity .9s ease}
.hero-stack.rot .hero-layer.is-on{opacity:1}
.hero-text{text-align:right}
.hero-text h1{
  margin:0 0 .7rem;
  font-size:clamp(1.7rem,3.6vw,2.7rem);
  line-height:1.22;
  letter-spacing:-.015em;
  font-weight:700;
}
.hero-text p{
  margin:0 0 0 auto;
  max-width:36ch;
  color:var(--mute);
  font-size:1.05rem;
}

/* ---------- 主体：主栏 + 右侧栏 ---------- */
main{
  display:grid;
  grid-template-columns:minmax(0,1fr) 300px;
  gap:1.8rem;
  align-items:start;
  max-width:1320px;
  margin:0 auto;
  padding:1.2rem 1rem 2.6rem;
}
main > div{grid-column:1;min-width:0}
main > aside{
  grid-column:2;
  grid-row:1 / span 120;
  align-self:start;
  position:sticky;
  top:92px;
  z-index:4;
}

div > section{
  position:relative;
  background:var(--paper);
  border:1px solid var(--line);
  border-bottom:4px solid var(--ink);
  box-shadow:var(--e2);
  padding:1.5rem 1.4rem;
  margin:1.4rem 0;
  z-index:1;
  scroll-margin-top:104px;
}
div > section:nth-child(even){margin-left:14px;z-index:2;box-shadow:var(--e3)}
div > section:nth-child(3n){z-index:3;box-shadow:var(--e4)}
div h2{
  margin:0 0 .8rem;
  font-size:clamp(1.3rem,2.3vw,1.62rem);
  line-height:1.34;
  letter-spacing:-.012em;
  font-weight:700;
}
div h2 span{border-bottom:3px solid var(--ink);padding-bottom:.1em}
div h3{
  margin:1.3rem 0 .5rem;
  font-size:1.16rem;
  line-height:1.4;
  font-weight:700;
}
div h3 span{border-bottom:2px solid var(--ink);padding-bottom:.08em}
div p{margin:0 0 .9rem;font-size:1.05rem}
div p:last-child{margin-bottom:0}
div ul,div ol{margin:0 0 .9rem;padding-left:1.3em}
div li{margin:.25rem 0;font-size:1.03rem}
div blockquote{
  margin:1rem 0;
  padding:.7rem 1rem;
  background:var(--grey);
  border-left:4px solid var(--ink);
}
div strong{font-weight:700}
div table{width:100%;border-collapse:collapse;margin:1rem 0;font-size:1rem}
div th,div td{border:1px solid var(--line);padding:.5rem .6rem;text-align:left}
div th{background:var(--grey)}
div img{display:block;max-width:100%;height:auto;margin:1rem 0;box-shadow:var(--e1)}
div figure{margin:1rem 0}
div a{text-decoration-thickness:1px;text-underline-offset:3px}

/* ---------- 侧栏 ---------- */
.rail{display:grid;gap:1rem}
.rail-card{
  background:var(--paper);
  border:1px solid var(--line);
  border-bottom:4px solid var(--ink);
  box-shadow:var(--e2);
  padding:1rem 1rem 1.1rem;
}
.rail-card h2,.rail-card h3{
  margin:0 0 .6rem;
  font-size:1rem;
  font-weight:700;
  letter-spacing:.02em;
}
.rail-card h2 span,.rail-card h3 span{border-bottom:2px solid var(--ink);padding-bottom:.1em}
.rail-card--tight{padding-bottom:1rem}
.rail-list{margin:0;padding:0;list-style:none;counter-reset:r}
.rail-list li a{
  display:flex;
  align-items:center;
  gap:.5rem;
  min-height:42px;
  font-size:1rem;
  text-decoration:none;
  border-bottom:1px solid var(--line);
}
.rail-list li:last-child a{border-bottom:0}
.rail-list li a::before{
  counter-increment:r;
  content:counter(r,decimal-leading-zero);
  font-size:.95rem;
  color:var(--mute);
  font-variant-numeric:tabular-nums;
}
.rail-list li a:hover{background:var(--grey)}
.rail-btn{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  min-height:44px;
  padding:.4rem 1.1rem;
  background:var(--ink);
  color:#fff;
  text-decoration:none;
  box-shadow:var(--e2);
  font-size:1rem;
}

/* ---------- 页脚 ---------- */
.foot{
  position:relative;
  z-index:5;
  margin-top:2rem;
  padding:2rem 1rem 1.3rem;
  background:var(--grey);
  border-top:1px solid var(--line);
  box-shadow:0 -10px 30px rgba(0,0,0,.05);
}
.foot-grid{display:grid;gap:1.1rem;max-width:1320px;margin:0 auto}
.foot-id{font-style:normal}
.foot-brand{
  display:block;
  font-size:clamp(2rem,8vw,4.4rem);
  line-height:.98;
  font-weight:700;
  letter-spacing:-.035em;
}
.foot-quick{display:flex;flex-wrap:wrap;gap:1.1rem;margin:0;padding:0;list-style:none}
.foot-quick a{
  display:inline-flex;
  align-items:center;
  min-height:44px;
  font-size:1rem;
  text-decoration:none;
  border-bottom:2px solid var(--ink);
}
.foot-nav h2{margin:0 0 .6rem;font-size:1rem;font-weight:700;letter-spacing:.02em}
.foot-nav h2 span{border-bottom:2px solid var(--ink);padding-bottom:.1em}
.foot-nav dl{
  display:grid;
  grid-template-columns:2.4rem minmax(0,1fr);
  gap:.1rem .6rem;
  margin:0;
  max-width:420px;
}
.foot-nav dt{font-size:1rem;color:var(--mute);font-variant-numeric:tabular-nums;line-height:1.5}
.foot-nav dd{margin:0}
.foot-nav dd a{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  font-size:1rem;
  text-decoration:none;
}
.foot-nav dd a:hover{text-decoration:underline}
.foot-copy{
  max-width:1320px;
  margin:1.2rem auto 0;
  padding-top:.9rem;
  border-top:1px solid var(--line);
  font-size:1rem;
  color:var(--mute);
}

/* ---------- 滚动出现 ---------- */
@media (prefers-reduced-motion: no-preference){
  html.js .rv{opacity:0;transform:translateY(18px)}
  html.js .rv.in{opacity:1;transform:none;transition:opacity .5s ease,transform .5s ease}
}

@media (prefers-reduced-motion: reduce){
  html{scroll-behavior:auto}
  .hero-stack.rot .hero-layer{transition:none}
}

/* ---------- 断点 ---------- */
@media (max-width:960px){
  main{grid-template-columns:minmax(0,1fr)}
  main > aside{grid-column:1;grid-row:auto;position:static}
  .hero{grid-template-columns:minmax(0,1fr);min-height:0;gap:1rem}
  .hero-frame{aspect-ratio:16/10}
  .hero-text{text-align:left}
  .hero-text p{margin-left:0;max-width:none}
  div > section:nth-child(even){margin-left:0}
}
@media (max-width:820px){
  .topnav{padding:.3rem .5rem;gap:.1rem}
  .topnav .side{flex:1 0 100%;justify-content:center}
  .topnav .side.left{order:1}
  .brand{order:0;flex:1 0 100%;justify-content:center;box-shadow:none;border-bottom:1px solid var(--line);background:transparent;padding:.4rem .5rem}
  .topnav .side.right{order:2}
  .topnav .lnk{font-size:1rem;padding:.25rem .45rem}
  div > section{padding:1.2rem 1rem}
  .foot{padding:1.6rem 1rem 1.2rem}
}
@media (max-width:420px){
  .topnav .side{gap:0}
  .topnav .lnk{padding:.25rem .35rem}
  .topnav .lnk::before{margin-right:.32rem;width:5px;height:5px}
}

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