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

:root{
  --ink:#1f1f1f;
  --paper:#ffffff;
  --wash:#f5f5f5;
  --soft:#fcfcfc;
  --mute:#6a6a6a;
  --dash:#dcdcdc;
  --r:28px;
  --bar:236px;
  --sans:'Fira Sans','PingFang SC','Hiragino Sans GB','Microsoft YaHei',system-ui,sans-serif;
  --mono:'Fira Code',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(--wash);
  color:var(--ink);
  font-family:var(--sans);
  font-size:17px;
  line-height:1.65;
  overflow-wrap:break-word;
}

:focus-visible{ outline:3px solid #8a8a8a; outline-offset:2px; border-radius:8px }

/* 左侧固定栏 */
.bar{
  position:fixed;
  inset:0 auto 0 0;
  width:var(--bar);
  z-index:20;
  display:flex;
  flex-direction:column;
  gap:18px;
  padding:20px 16px 24px;
  background:var(--paper);
  border-right:2px solid var(--ink);
  overflow-y:auto;
}

.bar-top{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:10px;
}

.mark{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  width:44px;
  height:44px;
  min-height:44px;
  border:2px solid var(--ink);
  border-radius:14px;
  background:var(--wash);
  text-decoration:none;
  color:var(--ink);
  overflow:hidden;
  flex:0 0 auto;
}

.mark span{
  font-family:var(--mono);
  font-weight:700;
  font-size:19px;
  line-height:1;
}

.mark img{ width:100%; height:100%; object-fit:contain; display:block }

.mark:hover{ background:var(--ink); color:var(--paper) }

.cta{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  min-height:44px;
  padding:0 16px;
  border:2px solid var(--ink);
  border-radius:999px;
  background:var(--ink);
  color:var(--paper);
  font-size:16px;
  font-weight:500;
  text-decoration:none;
}

.cta:hover{ background:var(--paper); color:var(--ink) }

.bar nav p{
  margin:0;
  display:flex;
  flex-direction:column;
  gap:2px;
}

.bar nav a{
  display:flex;
  align-items:center;
  min-height:44px;
  padding:8px 12px;
  border:2px solid transparent;
  border-radius:14px;
  color:var(--ink);
  text-decoration:none;
  font-size:16px;
  letter-spacing:.01em;
}

.bar nav a:hover{ background:var(--wash); border-color:var(--ink) }

/* 页面骨架 */
.shell{
  margin-left:var(--bar);
  max-width:1180px;
  padding:24px clamp(16px,3vw,36px) 0;
  display:flex;
  flex-direction:column;
  gap:20px;
}

/* 首屏 */
.hero{
  display:grid;
  grid-template-columns:minmax(0,.85fr) minmax(0,1.15fr);
  align-items:center;
  gap:clamp(16px,3vw,32px);
  min-height:64vh;
  padding:clamp(20px,3vw,36px);
  background:var(--paper);
  border:2px solid var(--ink);
  border-radius:var(--r);
}

.hero:hover{ background:var(--soft) }

.hero-fig{
  aspect-ratio:4 / 3;
  border:2px solid var(--ink);
  border-radius:20px;
  overflow:hidden;
  background:var(--wash);
}

.hero-fig img{ display:block; width:100%; height:100%; object-fit:cover }

.hero-copy{
  display:flex;
  flex-direction:column;
  align-items:center;
  gap:14px;
  text-align:center;
}

.eyebrow{
  margin:0;
  font-family:var(--mono);
  font-size:16px;
  letter-spacing:.08em;
  color:var(--mute);
}

.hero h1{
  margin:0;
  font-size:clamp(1.9rem,4.6vw,3.1rem);
  line-height:1.14;
  letter-spacing:-.01em;
  font-weight:700;
}

.lede{
  margin:0;
  max-width:44ch;
  font-size:17px;
  color:#3a3a3a;
}

/* 内容区 */
main{
  display:grid;
  grid-template-columns:240px minmax(0,1fr);
  gap:20px;
  align-items:start;
}

.side{
  position:sticky;
  top:24px;
  display:flex;
  flex-direction:column;
  gap:10px;
  padding:20px 18px;
  background:var(--paper);
  border:2px solid var(--ink);
  border-radius:var(--r);
}

.side h2{
  margin:0;
  font-family:var(--mono);
  font-size:16px;
  font-weight:600;
  letter-spacing:.05em;
}

.side h2:not(:first-child){ margin-top:14px }

.side h2 span{
  display:inline-block;
  padding-bottom:3px;
  border-bottom:2px solid var(--ink);
}

.side-nav{
  margin:0;
  display:flex;
  flex-direction:column;
  gap:2px;
}

.side-nav a{
  display:flex;
  align-items:center;
  min-height:40px;
  padding:6px 10px;
  border-radius:12px;
  color:var(--ink);
  text-decoration:none;
  font-size:16px;
}

.side-nav a:hover{ background:var(--wash) }

.side-note{
  margin:0;
  font-size:16px;
  color:#3a3a3a;
}

.body{
  display:flex;
  flex-direction:column;
  gap:20px;
  min-width:0;
}

.body > article{
  padding:clamp(20px,3vw,36px);
  background:var(--paper);
  border:2px solid var(--ink);
  border-radius:var(--r);
  scroll-margin-top:24px;
}

.body > article:hover{ background:var(--soft) }

.body h2{
  margin:0 0 .55em;
  font-size:clamp(1.35rem,2.4vw,1.75rem);
  line-height:1.28;
  letter-spacing:.005em;
}

.body h3{
  margin:1.4em 0 .5em;
  font-size:1.16rem;
  line-height:1.35;
}

.body h2 span,
.body h3 span{
  border-bottom:2px solid var(--ink);
  padding-bottom:2px;
}

.body p{ margin:0 0 1em }
.body p:last-child{ margin-bottom:0 }

.body ul,
.body ol{ margin:0 0 1em; padding-left:1.35em }
.body li{ margin:.35em 0 }

.body a{
  color:var(--ink);
  text-decoration:underline;
  text-underline-offset:3px;
}

.body a:hover{ background:var(--wash) }

.body img{
  display:block;
  max-width:100%;
  height:auto;
  margin:1em 0;
  border:2px solid var(--ink);
  border-radius:18px;
}

.body blockquote{
  margin:0 0 1em;
  padding:2px 0 2px 16px;
  border-left:4px solid var(--ink);
  color:#3a3a3a;
}

.body code,
.body pre{ font-family:var(--mono); font-size:15.5px }

.body pre{
  overflow-x:auto;
  padding:14px 16px;
  background:var(--wash);
  border:2px solid var(--ink);
  border-radius:16px;
}

/* 页脚 */
footer{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:10px;
  margin-top:8px;
  padding:16px 0 28px;
  border-top:2px solid var(--ink);
  font-size:16px;
}

footer p{ margin:0; color:#3a3a3a }

footer small{ font-size:16px }

footer small a{
  display:inline-flex;
  align-items:center;
  min-height:40px;
  padding:6px 14px;
  border:2px solid var(--ink);
  border-radius:999px;
  color:var(--ink);
  text-decoration:none;
}

footer small a:hover{ background:var(--paper) }

/* 滚动出现 */
.reveal{
  opacity:0;
  transform:translateY(16px);
  transition:opacity .5s ease, transform .5s ease;
}

.reveal.in{ opacity:1; transform:none }

/* 窄屏 */
@media (max-width:900px){
  .bar{
    position:sticky;
    inset:auto;
    top:0;
    width:auto;
    gap:8px;
    padding:10px 14px;
    border-right:none;
    border-bottom:2px solid var(--ink);
    overflow:visible;
  }

  .bar nav p{
    flex-direction:row;
    gap:6px;
    overflow-x:auto;
    padding-bottom:2px;
  }

  .bar nav a{
    white-space:nowrap;
    padding:8px 12px;
    border-color:var(--dash);
  }

  .shell{
    margin-left:0;
    padding:14px 14px 0;
  }

  .hero{
    grid-template-columns:1fr;
    min-height:0;
  }

  .hero-copy{
    order:-1;
    align-items:flex-start;
    text-align:left;
  }

  .lede{ max-width:none }

  .hero-fig{ aspect-ratio:16 / 9 }

  main{ grid-template-columns:1fr }

  .side{ position:static }

  .body > article{ scroll-margin-top:132px }

  footer{ padding-bottom:20px }
}

@media (prefers-reduced-motion:reduce){
  html{ scroll-behavior:auto }
  .reveal{ opacity:1; transform:none; transition:none }
  .hero,
  .body > article{ transition:none }
}

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