@import url('https://fonts.googleapis.com/css2?family=Open+Sans:wght@300;400;500;600;700&family=Poppins:wght@400;500;600;700&display=swap');

:root{
  --ink:#000;
  --paper:#fff;
  --rail:264px;
  --sans:'Open Sans',-apple-system,'Segoe UI',Roboto,'Helvetica Neue',Arial,sans-serif;
  --disp:'Poppins','Open Sans',-apple-system,'Segoe UI',Roboto,'Helvetica Neue',Arial,sans-serif;
}

*,*::before,*::after{box-sizing:border-box}

html{
  -webkit-text-size-adjust:100%;
  scroll-behavior:smooth;
}

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  font-size:17px;
  font-weight:400;
  line-height:1.7;
  overflow-x:hidden;
}

a{color:inherit;text-decoration:none}
img{display:block;max-width:100%;height:auto}
menu,ol,ul{margin:0;padding:0;list-style:none}
p{margin:0}

main{margin-left:var(--rail)}
section[id]{scroll-margin-top:32px}

/* ---------- 左侧竖排导航 ---------- */
.masthead{
  position:fixed;
  top:0;
  left:0;
  bottom:0;
  width:var(--rail);
  display:flex;
  flex-direction:column;
  padding:24px 20px 20px;
  background:var(--paper);
  border-right:2px solid var(--ink);
  z-index:30;
  overflow-y:auto;
}

.brand{
  display:flex;
  align-items:flex-start;
  gap:10px;
  min-height:44px;
  padding:6px 0 18px;
  font-family:var(--disp);
  font-size:22px;
  font-weight:700;
  line-height:1.15;
  letter-spacing:-.025em;
  border-bottom:2px solid var(--ink);
}

.brand .mark{
  flex:0 0 auto;
  width:14px;
  height:14px;
  margin-top:6px;
  background:var(--ink);
}

.brand-mark{
  flex:0 0 auto;
  width:16px;
  height:16px;
  margin-top:5px;
  object-fit:contain;
}

.brand:hover .mark{transform:rotate(45deg)}
.brand .mark{transition:transform .25s ease}

.rail-contact{
  align-self:flex-start;
  display:inline-flex;
  align-items:center;
  min-height:44px;
  margin-top:14px;
  padding:0 12px 0 0;
  font-size:16px;
  font-weight:600;
  letter-spacing:.02em;
}
.rail-contact span{border-bottom:2px solid var(--ink)}
.rail-contact:hover span{background:var(--ink);color:var(--paper)}

.menu{margin-top:22px}

.menu summary{
  display:flex;
  align-items:center;
  justify-content:space-between;
  min-height:44px;
  padding:0;
  font-family:var(--disp);
  font-size:14px;
  font-weight:600;
  letter-spacing:.3em;
  cursor:pointer;
  border-bottom:1px solid var(--ink);
  list-style:none;
}
.menu summary::-webkit-details-marker{display:none}
.menu summary::after{
  content:"+";
  font-size:18px;
  line-height:1;
  letter-spacing:0;
}
.menu[open] summary::after{content:"−"}

.menu-list{margin-top:4px}

.menu-list a{
  display:flex;
  align-items:center;
  gap:10px;
  min-height:44px;
  padding:10px 0;
  font-size:17px;
  line-height:1.35;
  border-bottom:1px solid rgba(0,0,0,.18);
}
.menu-list .ico{
  flex:0 0 auto;
  width:10px;
  height:10px;
  transition:transform .2s ease;
}
.menu-list a:hover .lbl{
  text-decoration:underline;
  text-decoration-thickness:2px;
  text-underline-offset:4px;
}
.menu-list a:hover .ico{transform:rotate(90deg)}

/* ---------- 首屏 ---------- */
.hero{
  position:relative;
  min-height:100vh;
  display:grid;
  grid-template-columns:repeat(12,1fr);
  align-content:center;
  overflow:hidden;
  isolation:isolate;
  background:var(--ink);
  border-bottom:2px solid var(--ink);
}

.hero-media{
  position:absolute;
  inset:0;
  margin:0;
  z-index:-2;
  background:
    repeating-linear-gradient(135deg,#111 0 18px,#1c1c1c 18px 36px);
}

.hero-media img{
  width:100%;
  height:100%;
  object-fit:cover;
  filter:grayscale(1) contrast(1.08);
  will-change:transform;
}

.hero-media::after{
  content:"";
  position:absolute;
  inset:0;
  background:linear-gradient(100deg,rgba(0,0,0,.94) 0%,rgba(0,0,0,.72) 46%,rgba(0,0,0,.3) 100%);
}

.hero::after{
  content:"";
  position:absolute;
  left:0;
  right:0;
  bottom:-1px;
  height:72px;
  background:var(--paper);
  clip-path:polygon(0 100%,100% 0,100% 100%);
  pointer-events:none;
}

.hero-copy{
  position:relative;
  z-index:1;
  grid-column:4 / -1;
  padding:0 64px 0 0;
  color:var(--paper);
  text-align:right;
}

.hero-copy h1{
  margin:0 0 24px;
  font-family:var(--disp);
  font-size:clamp(34px,5.4vw,74px);
  font-weight:700;
  line-height:1.02;
  letter-spacing:-.03em;
  text-wrap:balance;
}

.hero-desc{
  max-width:52ch;
  margin:0 0 0 auto;
  font-size:clamp(16px,1.4vw,20px);
  font-weight:300;
  line-height:1.6;
  color:rgba(255,255,255,.88);
}

/* ---------- 正文 + 右侧栏 ---------- */
.band{
  display:grid;
  grid-template-columns:minmax(0,1fr) 248px;
  gap:64px;
  padding:88px 64px 96px;
  border-bottom:2px solid var(--ink);
}

.prose{min-width:0;max-width:70ch}

.prose > section{padding-top:4px}
.prose > section:not(:first-child){
  margin-top:64px;
  padding-top:44px;
  border-top:1px solid rgba(0,0,0,.2);
}
.prose > section:first-child > h2:first-child{margin-top:0}

.prose h2{
  margin:72px 0 0;
  font-family:var(--disp);
  font-size:clamp(25px,3vw,40px);
  font-weight:700;
  line-height:1.08;
  letter-spacing:-.025em;
}

.prose h3{
  margin:40px 0 0;
  font-family:var(--disp);
  font-size:21px;
  font-weight:600;
  line-height:1.25;
  letter-spacing:-.01em;
}

.prose hr{
  margin:14px 0 22px;
  border:0;
  border-top:2px solid var(--ink);
}

.prose p{
  margin:18px 0;
  font-size:18px;
  line-height:1.78;
}

.prose h2 + hr + p,
.prose h3 + hr + p{margin-top:0}

.prose a{
  text-decoration:underline;
  text-decoration-thickness:1px;
  text-underline-offset:3px;
}
.prose a:hover{background:var(--ink);color:var(--paper);text-decoration:none}

.prose ul,.prose ol{margin:18px 0;padding-left:1.4em;list-style:revert}
.prose li{margin:8px 0;font-size:18px;line-height:1.7}

.prose blockquote{
  margin:28px 0;
  padding:4px 0 4px 20px;
  border-left:4px solid var(--ink);
  font-size:18px;
  line-height:1.7;
}

.prose figure{margin:28px 0;border:2px solid var(--ink)}
.prose figcaption{padding:8px 12px;border-top:1px solid var(--ink);font-size:15px;line-height:1.5}

.prose table{width:100%;border-collapse:collapse;margin:24px 0;font-size:16px}
.prose th,.prose td{padding:10px 12px;border-bottom:1px solid rgba(0,0,0,.25);text-align:left;vertical-align:top}
.prose th{font-family:var(--disp);font-size:15px;font-weight:600}

.prose strong{font-weight:700}

/* 侧栏 */
.side{min-width:0}
.side-in{position:sticky;top:32px}

.side h2{
  margin:0;
  font-family:var(--disp);
  font-size:14px;
  font-weight:600;
  letter-spacing:.3em;
}

.side hr{
  margin:12px 0 6px;
  border:0;
  border-top:2px solid var(--ink);
}

.side-list{counter-reset:s}
.side-list li{counter-increment:s;border-bottom:1px solid rgba(0,0,0,.2)}
.side-list a{
  display:flex;
  align-items:baseline;
  gap:10px;
  min-height:44px;
  padding:11px 0;
  font-size:16px;
  line-height:1.4;
}
.side-list a::before{
  content:counter(s,decimal-leading-zero);
  font-family:var(--disp);
  font-size:12px;
  font-weight:600;
  color:rgba(0,0,0,.55);
}
.side-list a:hover .lbl{
  text-decoration:underline;
  text-decoration-thickness:2px;
  text-underline-offset:4px;
}

/* ---------- 页脚 ---------- */
.foot{
  background:var(--ink);
  color:var(--paper);
}

.foot-cta{
  display:grid;
  grid-template-columns:1fr auto;
  align-items:end;
  gap:32px;
  padding:64px;
  border-bottom:1px solid rgba(255,255,255,.3);
}

.cta-big{
  margin:0;
  font-family:var(--disp);
  font-size:clamp(30px,4.4vw,54px);
  font-weight:700;
  line-height:1;
  letter-spacing:-.035em;
}

.cta-btn{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  min-height:52px;
  padding:0 26px;
  border:2px solid var(--paper);
  font-family:var(--disp);
  font-size:16px;
  font-weight:600;
  transition:background .2s ease,color .2s ease;
}
.cta-btn:hover{background:var(--paper);color:var(--ink)}

.foot-cols{
  display:grid;
  grid-template-columns:repeat(3,minmax(0,1fr));
  gap:32px;
  padding:56px 64px;
}

.foot-cols dt{
  margin-bottom:8px;
  font-family:var(--disp);
  font-size:13px;
  font-weight:600;
  letter-spacing:.28em;
  color:rgba(255,255,255,.6);
}

.foot-cols dd{margin:0}
.foot-cols dd a{
  display:inline-block;
  min-height:40px;
  padding:9px 0;
  font-size:16px;
  line-height:1.4;
  border-bottom:1px solid transparent;
}
.foot-cols dd a:hover{border-bottom-color:var(--paper)}

.foot-base{
  padding:22px 20px 40px;
  border-top:1px solid rgba(255,255,255,.2);
  text-align:center;
  font-size:15px;
  color:rgba(255,255,255,.72);
}

/* ---------- 中屏 ---------- */
@media (min-width:861px){
  .menu > menu{display:block}
}

@media (max-width:1180px){
  .hero-copy{padding-right:40px}
  .band{gap:40px;padding:64px 40px 80px;grid-template-columns:minmax(0,1fr) 220px}
  .foot-cta,.foot-cols{padding-left:40px;padding-right:40px}
}

/* ---------- 移动端 ---------- */
@media (max-width:860px){
  main{margin-left:0}
  section[id]{scroll-margin-top:84px}

  .masthead{
    position:sticky;
    top:0;
    left:auto;
    bottom:auto;
    width:auto;
    flex-direction:row;
    align-items:center;
    justify-content:space-between;
    gap:12px;
    padding:8px 16px;
    border-right:0;
    border-bottom:2px solid var(--ink);
  }

  .brand{
    flex:1 1 auto;
    min-width:0;
    align-items:center;
    padding:0;
    font-size:19px;
    border-bottom:0;
  }
  .brand .mark,.brand-mark{margin-top:0}

  .rail-contact{
    order:1;
    margin-top:0;
    padding:0 10px;
    font-size:15px;
  }

  .menu{order:2;margin-top:0;position:relative}
  .menu summary{
    justify-content:center;
    gap:8px;
    min-height:44px;
    padding:0 14px;
    border:2px solid var(--ink);
    font-size:15px;
    letter-spacing:.16em;
  }
  .menu summary::after{font-size:16px}
  .menu[open] summary{background:var(--ink);color:var(--paper)}

  .menu-list{
    position:absolute;
    top:calc(100% + 8px);
    right:0;
    width:min(76vw,300px);
    margin:0;
    padding:8px 16px 12px;
    background:var(--paper);
    border:2px solid var(--ink);
    max-height:70vh;
    overflow-y:auto;
  }
  .menu-list a{font-size:16px}
  .menu-list li:last-child a{border-bottom:0}

  .hero{align-content:start;min-height:88vh}
  .hero::after{height:44px}
  .hero-copy{
    grid-column:1 / -1;
    padding:88px 20px 96px;
    text-align:left;
  }
  .hero-desc{margin-left:0;max-width:36ch}
  .hero-copy h1{font-size:clamp(30px,9vw,44px)}

  .band{
    grid-template-columns:minmax(0,1fr);
    gap:44px;
    padding:44px 20px 64px;
  }
  .side-in{position:static}
  .prose p,.prose li,.prose blockquote{font-size:17px}

  .foot-cta{
    grid-template-columns:1fr;
    align-items:start;
    gap:20px;
    padding:44px 20px;
  }
  .cta-btn{align-self:start}
  .foot-cols{grid-template-columns:1fr;gap:8px;padding:32px 20px}
  .foot-cols dt{margin-top:16px}
  .foot-base{font-size:14px;padding-bottom:32px}
}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *{transition:none !important;animation:none !important}
  .hero-img{transform:none !important}
}

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