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

:root{
  --ink:#000000;
  --paper:#ffffff;
  --graphite:#3b3b3b;
  --rail:300px;
  --pad:clamp(1.4rem,4vw,3.6rem);
  --gap:clamp(1.6rem,4vw,3.4rem);
  --sans:'Exo',system-ui,-apple-system,'Segoe UI','PingFang SC','Microsoft YaHei',sans-serif;
  --mono:'Roboto Mono',ui-monospace,SFMono-Regular,Menlo,monospace;
}

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

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

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  font-size:17px;
  line-height:1.72;
  letter-spacing:.005em;
  -webkit-font-smoothing:antialiased;
}

img,video,svg{max-width:100%}
img{display:block;height:auto;border-radius:4px}
a{color:var(--ink);text-decoration-thickness:2px;text-underline-offset:3px}
h1,h2,h3,h4{margin:0;font-weight:900;letter-spacing:-.045em;line-height:1.04;text-wrap:balance}
p{margin:0 0 1.05rem}
ul,ol{margin:0;padding:0;list-style:none}
.sr{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}

/* 左侧固定竖排轨道 */
.rail{
  position:fixed;
  top:0;bottom:0;left:0;
  z-index:30;
  width:var(--rail);
  display:flex;
  flex-direction:column;
  gap:1.5rem;
  padding:2rem 1.5rem 1.6rem;
  background:var(--paper);
  border-right:2px solid var(--ink);
  overflow-y:auto;
  overflow-x:hidden;
}

.brand{
  display:flex;
  align-items:center;
  min-height:48px;
  padding:.2rem 0;
  font-size:1.18rem;
  font-weight:700;
  line-height:1.15;
  letter-spacing:-.03em;
  text-decoration:none;
  border-bottom:2px solid var(--ink);
  padding-bottom:.9rem;
}

.railnav ol{display:flex;flex-direction:column;gap:.5rem}

.railnav a{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:.5rem 1.05rem;
  border:2px solid var(--ink);
  border-radius:999px;
  font-size:1rem;
  font-weight:600;
  letter-spacing:-.01em;
  text-decoration:none;
  transition:background .18s ease,color .18s ease,transform .18s ease;
}
.railnav a:hover,
.railnav a:focus-visible{background:var(--ink);color:var(--paper);transform:translateX(4px)}

.rail-cta{
  margin-top:auto;
  display:flex;
  align-items:center;
  justify-content:center;
  min-height:48px;
  padding:.6rem 1rem;
  background:var(--ink);
  color:var(--paper);
  border-radius:999px;
  font-size:1rem;
  font-weight:700;
  text-decoration:none;
  transition:background .18s ease,color .18s ease;
}
.rail-cta:hover,.rail-cta:focus-visible{background:var(--paper);color:var(--ink);box-shadow:inset 0 0 0 2px var(--ink)}

main{margin-left:var(--rail)}
.wrap{max-width:1120px;margin:0 auto;padding:0 var(--pad)}

/* 首屏 */
.hero{
  position:relative;
  overflow:hidden;
  min-height:45vh;
  display:flex;
  align-items:flex-end;
  justify-content:flex-end;
  gap:1.1rem;
  padding:clamp(2.6rem,6vw,5rem) 0 clamp(2rem,4vw,3.2rem);
  border-bottom:2px solid var(--ink);
}

.hero-num{
  position:absolute;
  left:-.04em;
  bottom:-.18em;
  font-family:var(--mono);
  font-size:clamp(8rem,22vw,15rem);
  font-weight:700;
  letter-spacing:-.09em;
  line-height:.78;
  opacity:.07;
  transform:translate3d(0,var(--py,0),0);
  pointer-events:none;
  user-select:none;
}

.hero-icon{
  flex:0 0 auto;
  width:58px;height:58px;
  display:grid;
  place-items:center;
  margin-bottom:.55rem;
  border:2px solid var(--ink);
  border-radius:4px;
}
.hero-icon svg{width:26px;height:26px}

.hero-copy{max-width:min(100%,44ch);text-align:right}
.hero-copy h1{font-size:clamp(2.3rem,6vw,4.5rem);line-height:.97}
.hero-sub{margin:.9rem 0 0;font-family:var(--mono);font-size:1rem;line-height:1.6;color:var(--graphite)}

/* 正文 + 右侧侧栏 */
.stage{
  display:grid;
  grid-template-columns:minmax(0,1fr) 252px;
  gap:var(--gap);
  padding:clamp(2rem,4vw,3.4rem) 0 clamp(2.8rem,5vw,4.4rem);
}

.content{min-width:0}

.content div{padding-bottom:1.4rem;margin-bottom:2.6rem;border-bottom:1px solid rgba(0,0,0,.13)}
.content div:last-child{border-bottom:0;margin-bottom:0}

small{
  display:block;
  font-family:var(--mono);
  font-size:.95rem;
  line-height:1.5;
  letter-spacing:.16em;
  color:var(--graphite);
  margin-bottom:.5rem;
}

.content h2,.side h2{font-size:clamp(1.5rem,3.4vw,2.3rem);margin:2.6rem 0 1rem}
.content h3{font-size:clamp(1.2rem,2.3vw,1.5rem);margin:1.8rem 0 .7rem}
small + h2,small + h3{margin-top:0}

.content p,.content li{line-height:1.78}
.content ul{list-style:disc;padding-left:1.3rem;margin:0 0 1.05rem}
.content ol{list-style:decimal;padding-left:1.3rem;margin:0 0 1.05rem}
.content li{margin:.35rem 0}
.content a{font-weight:600}
.content blockquote{
  margin:1.4rem 0;
  padding:.2rem 0 .2rem 1.1rem;
  border-left:4px solid var(--ink);
  font-size:1.05rem;
}
.content img{margin:1.2rem 0}
[id]{scroll-margin-top:2rem}

/* 侧栏 */
.side{
  position:sticky;
  top:2rem;
  align-self:start;
  border-top:2px solid var(--ink);
  padding-top:1rem;
  font-size:1rem;
}
.side h2{font-size:1.15rem;letter-spacing:-.02em;margin:0 0 .5rem}
.side ol{display:flex;flex-direction:column}
.side a{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:.4rem 0;
  border-bottom:1px solid rgba(0,0,0,.14);
  font-weight:600;
  text-decoration:none;
}
.side a:hover,.side a:focus-visible{text-decoration:underline}

/* 页脚 */
footer.foot{
  margin-left:var(--rail);
  background:var(--ink);
  color:var(--paper);
  padding:clamp(2.4rem,4.6vw,3.8rem) var(--pad) 1.6rem;
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  gap:clamp(1.5rem,3vw,2.6rem);
}
footer.foot a{color:var(--paper);text-decoration:none}
footer.foot a:hover{text-decoration:underline}
footer.foot small{color:#9c9c9c}

.fbrand{margin:0 0 .6rem;font-size:1.12rem;font-weight:700;letter-spacing:-.03em;line-height:1.2}
.fdesc{margin:0;font-size:1rem;line-height:1.6;color:#c9c9c9}
.fh{margin:0 0 .5rem;font-family:var(--mono);font-size:.95rem;font-weight:500;letter-spacing:.16em;color:#9c9c9c}
.flist a,.flink{
  display:flex;
  align-items:center;
  min-height:44px;
  font-size:1rem;
  font-weight:600;
  border-bottom:1px solid rgba(255,255,255,.18);
}
.fsub{display:flex;flex-direction:column;gap:.55rem}
.fsub input{
  min-height:46px;
  padding:.55rem .85rem;
  font-family:var(--sans);
  font-size:1rem;
  color:var(--paper);
  background:transparent;
  border:2px solid #ffffff;
  border-radius:4px;
}
.fsub input::placeholder{color:#8d8d8d}
.fsub button{
  min-height:46px;
  padding:.55rem 1rem;
  font-family:var(--sans);
  font-size:1rem;
  font-weight:700;
  color:var(--ink);
  background:var(--paper);
  border:2px solid var(--paper);
  border-radius:999px;
  cursor:pointer;
}
.fsub button:hover{background:transparent;color:var(--paper)}

.foot-base{
  grid-column:1/-1;
  display:flex;
  flex-wrap:wrap;
  justify-content:space-between;
  align-items:center;
  gap:1rem;
  margin-top:.6rem;
  padding-top:1rem;
  border-top:1px solid rgba(255,255,255,.28);
  font-family:var(--mono);
  font-size:1rem;
}
.copy{margin:0}
.baselinks{margin:0;display:flex;gap:1.4rem}
.baselinks a{display:flex;align-items:center;min-height:44px;font-weight:600}

/* 动效 */
@media (prefers-reduced-motion:no-preference){
  .js footer.foot > div,
  .js .content > div{
    opacity:0;
    transform:translateY(20px);
    transition:opacity .55s ease,transform .55s cubic-bezier(.2,.7,.3,1);
  }
  .js footer.foot > div.in,
  .js .content > div.in{opacity:1;transform:none}
}

/* 平板与手机 */
@media (max-width:1000px){
  .stage{grid-template-columns:minmax(0,1fr) 220px;gap:1.6rem}
}

@media (max-width:900px){
  .rail{
    position:sticky;
    top:0;
    width:auto;
    flex-direction:row;
    align-items:center;
    gap:.6rem;
    padding:.6rem .8rem;
    border-right:0;
    border-bottom:2px solid var(--ink);
    overflow-x:auto;
    overflow-y:hidden;
  }
  .brand{
    flex:0 0 auto;
    min-height:44px;
    padding:0 0 0 0;
    border-bottom:0;
    font-size:1.02rem;
    white-space:nowrap;
  }
  .railnav{min-width:0}
  .railnav ol{flex-direction:row;gap:.45rem}
  .railnav a{
    min-height:44px;
    padding:.45rem .9rem;
    white-space:nowrap;
    font-size:1rem;
  }
  .railnav a:hover{transform:none}
  .rail-cta{margin-top:0;flex:0 0 auto;min-height:44px;white-space:nowrap}
  main,footer.foot{margin-left:0}
  .stage{grid-template-columns:1fr;gap:1.4rem}
  .side{position:static;order:2}
  .hero{min-height:auto;flex-direction:column;align-items:flex-end;gap:.5rem;padding-top:2.2rem}
  .hero-num{font-size:clamp(6.5rem,26vw,10rem)}
  .hero-copy{text-align:right;max-width:100%}
  footer.foot{grid-template-columns:repeat(2,minmax(0,1fr))}
  [id]{scroll-margin-top:92px}
}

@media (max-width:520px){
  body{font-size:16px}
  footer.foot{grid-template-columns:1fr}
  .baselinks{gap:1rem}
  .content div{padding-bottom:1.1rem;margin-bottom:2rem}
}

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