:root{
  --paper:#fdfbf7;
  --paper-2:#f5f5f5;
  --ink:#1a1a1a;
  --muted:#6b6b6b;
  --line:#e0e0e0;
  --line-2:#c9c9c9;
  --rail:184px;
  --radius:10px;
  --maxw:1180px;
}
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;
  padding-left:var(--rail);
  background:var(--paper);
  color:var(--ink);
  font-family:"Inter",-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  font-size:17px;
  line-height:1.7;
  letter-spacing:.005em;
  overflow-wrap:break-word;
  -webkit-font-smoothing:antialiased;
  transition:none;
}
body::before{
  content:"";
  position:fixed;
  inset:0;
  z-index:0;
  pointer-events:none;
  opacity:.5;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='180' height='180'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='3' stitchTiles='stitch'/%3E%3CfeColorMatrix type='saturate' values='0'/%3E%3C/filter%3E%3Crect width='180' height='180' filter='url(%23n)' opacity='0.07'/%3E%3C/svg%3E");
}
img{display:block;max-width:100%;height:auto}
a{color:inherit;text-decoration:none}
a:hover{text-decoration:underline;text-underline-offset:3px}
hr{border:0;border-top:1px solid var(--line);margin:22px 0}
button{font:inherit;cursor:pointer}
:focus-visible{outline:2px solid var(--ink);outline-offset:2px}
.vh{position:absolute;width:1px;height:1px;margin:-1px;padding:0;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}

/* ── 左侧竖排导航 ─────────────────────────── */
.rail{
  position:fixed;
  z-index:40;
  top:0;left:0;bottom:0;
  width:var(--rail);
  display:flex;
  flex-direction:column;
  align-items:center;
  gap:14px;
  padding:16px 12px 14px;
  background:var(--paper);
  border-right:1px solid var(--line);
  overflow-y:auto;
}
.mark{
  display:grid;
  place-items:center;
  width:48px;height:48px;
  flex:0 0 auto;
  color:var(--ink);
  border:1px solid var(--line-2);
  border-radius:var(--radius);
  background:var(--paper);
}
.mark:hover{border-color:var(--ink);text-decoration:none;background:var(--paper-2)}
.mark-img{width:26px;height:26px;object-fit:contain}
.rail-menu{display:flex;flex-direction:column;width:100%;gap:10px}
.rail-menu summary{
  list-style:none;
  cursor:pointer;
  display:grid;
  place-items:center;
  width:100%;
  min-height:40px;
  border:1px solid var(--line);
  border-radius:var(--radius);
  background:var(--paper);
}
.rail-menu summary::-webkit-details-marker{display:none}
.rail-menu summary:hover{border-color:var(--ink);background:var(--paper-2)}
.bars,.bars::before,.bars::after{display:block;width:16px;height:1.5px;background:var(--ink);content:""}
.bars::before{transform:translateY(-5px)}
.bars::after{transform:translateY(3.5px)}
.rail-list{list-style:none;margin:0;padding:0;display:grid;gap:3px;width:100%}
.rail-link{
  display:flex;
  align-items:center;
  gap:9px;
  min-height:42px;
  padding:9px 10px;
  font-size:.85rem;
  line-height:1.25;
  color:var(--ink);
  border:1px solid transparent;
  border-radius:8px;
}
.rail-link .ico{flex:0 0 auto;color:var(--muted)}
.rail-link:hover{background:var(--paper-2);border-color:var(--line);text-decoration:none}
.rail-link:hover .ico{color:var(--ink)}
.rail-search{display:flex;gap:6px;width:100%;padding-top:12px;margin-top:2px;border-top:1px solid var(--line)}
.rail-search input{
  flex:1 1 auto;min-width:0;min-height:40px;
  padding:6px 8px;
  font-family:inherit;font-size:.82rem;
  color:var(--ink);background:var(--paper);
  border:1px solid var(--line);border-radius:8px;
}
.rail-search input::placeholder{color:var(--muted)}
.rail-search button{
  min-width:40px;min-height:40px;
  padding:0 8px;
  font-size:.82rem;
  color:var(--paper);background:var(--ink);
  border:1px solid var(--ink);border-radius:8px;
}
.rail-search button:hover{background:#000}

/* ── 纸张主体 ─────────────────────────────── */
.sheet{
  position:relative;
  z-index:1;
  display:grid;
  grid-template-columns:minmax(0,1fr) 238px;
  gap:46px;
  align-items:start;
  max-width:var(--maxw);
  margin:0 auto;
  padding:0 34px;
}
.paper{min-width:0}

/* 首屏 */
.hero{
  display:grid;
  grid-template-columns:minmax(0,1fr) minmax(0,1fr);
  gap:34px;
  align-items:center;
  min-height:45vh;
  padding:34px 0 30px;
  border-bottom:1px solid var(--line);
}
.paper > .hero{border-top:0}
.hero-copy{text-align:center}
.hero h1{
  margin:0 0 14px;
  font-size:clamp(1.55rem,2.9vw,2.25rem);
  line-height:1.24;
  font-weight:600;
  letter-spacing:-.03em;
}
.hero-lede{
  margin:0 auto;
  max-width:32ch;
  font-size:.94rem;
  line-height:1.65;
  color:var(--muted);
}
.hero-fig{
  position:relative;
  margin:0;
  overflow:hidden;
  border:1px solid var(--line-2);
  border-bottom:3px solid var(--ink);
  border-radius:var(--radius);
  background:var(--paper-2);
  aspect-ratio:4/3;
}
.hero-fig.is-blank{background:var(--paper-2)}
.hero-img{width:100%;height:100%;object-fit:cover;transform:scale(1.04)}
.badge{
  position:absolute;
  left:12px;bottom:12px;
  padding:4px 10px;
  font-size:.76rem;
  letter-spacing:.1em;
  color:var(--ink);
  background:var(--paper);
  border:1px solid var(--ink);
  border-radius:var(--radius);
}

/* 正文区块 */
.paper > section{
  padding:38px 0;
  border-top:1px solid var(--line);
  scroll-margin-top:28px;
}
.paper > section.is-hit{outline:1px solid var(--ink);outline-offset:12px}
.paper h2{
  margin:0 0 14px;
  font-size:clamp(1.28rem,2.1vw,1.62rem);
  line-height:1.32;
  font-weight:600;
  letter-spacing:-.02em;
}
.paper h2 + hr{margin:-6px 0 22px}
.paper h3{margin:26px 0 10px;font-size:1.08rem;line-height:1.4;font-weight:600}
.paper p{margin:0 0 16px;max-width:64ch}
.paper ul,.paper ol{margin:0 0 16px;padding-left:1.25em}
.paper li{margin:0 0 7px}
.paper strong{font-weight:600}
.paper blockquote{
  margin:22px 0;
  padding:2px 0 2px 18px;
  border-left:2px solid var(--ink);
  color:var(--muted);
}
.paper figure{
  margin:24px 0;
  overflow:hidden;
  border:1px solid var(--line);
  border-bottom:3px solid var(--ink);
  border-radius:var(--radius);
  background:var(--paper-2);
}
.paper figcaption{padding:8px 12px;font-size:.84rem;color:var(--muted)}
.paper table{width:100%;border-collapse:collapse;font-size:.94rem;display:block;overflow-x:auto}
.paper th,.paper td{padding:10px 8px;text-align:left;border-bottom:1px solid var(--line)}
.paper pre{overflow-x:auto;padding:14px;background:var(--paper-2);border:1px solid var(--line);border-radius:var(--radius)}
.paper code{font-size:.9em}

/* 右侧批注栏 */
.notes{
  position:sticky;
  top:26px;
  align-self:start;
  padding-left:20px;
  border-left:1px solid var(--line);
  font-size:.9rem;
}
.notes h2{
  margin:0 0 10px;
  font-size:.8rem;
  font-weight:500;
  letter-spacing:.16em;
  color:var(--muted);
}
.notes h2 + hr{margin:0 0 12px}
.notes ol{list-style:none;margin:0;padding:0}
.notes li + li{border-top:1px solid var(--line)}
.notes a{display:block;padding:9px 0;min-height:40px;line-height:1.4}
.notes a:hover{text-decoration:none;color:var(--muted)}

/* ── 页脚 ─────────────────────────────────── */
.foot{
  position:relative;
  z-index:1;
  display:grid;
  grid-template-columns:1.5fr 1fr;
  gap:30px 40px;
  max-width:var(--maxw);
  margin:68px auto 0;
  padding:40px 34px 24px;
  border-top:2px solid var(--ink);
}
.foot-brand h2{margin:0 0 12px;font-size:1.02rem;font-weight:600;letter-spacing:-.01em}
.foot-brand h2 + hr,.foot-nav h2 + hr,.foot-sub h2 + hr{margin:0 0 12px}
.foot-brand p{margin:0;max-width:44ch;font-size:.9rem;color:var(--muted)}
.foot-nav h2,.foot-sub h2{margin:0 0 12px;font-size:.78rem;font-weight:500;letter-spacing:.16em;color:var(--muted)}
.foot-nav ul{list-style:none;margin:0;padding:0;display:grid;gap:2px}
.foot-nav a{display:inline-block;padding:8px 0;min-height:40px;font-size:.92rem}
.foot-sub{grid-column:1 / -1;padding-top:24px;border-top:1px solid var(--line)}
.sub-form{display:flex;flex-wrap:wrap;gap:8px;max-width:440px}
.sub-form input{
  flex:1 1 220px;min-width:0;min-height:42px;
  padding:8px 10px;
  font-family:inherit;font-size:.92rem;
  color:var(--ink);background:var(--paper);
  border:1px solid var(--line);border-radius:var(--radius);
}
.sub-form input::placeholder{color:var(--muted)}
.sub-form button{
  min-height:42px;padding:0 20px;
  font-size:.92rem;
  color:var(--paper);background:var(--ink);
  border:1px solid var(--ink);border-radius:var(--radius);
}
.sub-form button:hover{background:#000}
.foot-base{
  grid-column:1 / -1;
  display:flex;
  flex-wrap:wrap;
  justify-content:space-between;
  gap:10px;
  padding-top:16px;
  border-top:1px solid var(--line);
  font-size:.84rem;
  color:var(--muted);
}
.foot-base p{margin:0}
.foot-base a{display:inline-block;padding:8px 0;min-height:40px;color:var(--ink)}

/* ── 窄屏 ─────────────────────────────────── */
@media (max-width:900px){
  body{padding-left:0;padding-top:66px;font-size:16px}
  .rail{
    right:0;bottom:auto;
    width:auto;height:auto;
    flex-direction:row;
    flex-wrap:wrap;
    align-items:center;
    gap:8px;
    padding:8px 12px;
    border-right:0;
    border-bottom:1px solid var(--line);
    overflow:visible;
  }
  .mark{width:40px;height:40px;margin:0}
  .rail-menu{flex:1 1 100%;width:auto;gap:8px;display:flex;flex-wrap:wrap;align-items:center}
  .rail-menu summary{width:40px;margin-left:auto;border-radius:8px;padding:0}
  .rail-list{flex:1 1 100%;padding-top:8px;border-top:1px solid var(--line);background:var(--paper)}
  .rail-link{min-height:44px;font-size:.94rem;background:var(--paper)}
  .rail-search{flex:1 1 100%;margin-top:0;padding:0 0 6px;border-top:0}
  .sheet{grid-template-columns:minmax(0,1fr);gap:0;padding:0 18px}
  .hero{grid-template-columns:minmax(0,1fr);gap:20px;min-height:0;padding:22px 0 26px}
  .hero-fig{aspect-ratio:16/10}
  .paper > section{padding:30px 0;scroll-margin-top:78px}
  .notes{position:static;margin-top:28px;padding:22px 0 0;border-left:0;border-top:1px solid var(--line)}
  .foot{grid-template-columns:minmax(0,1fr);gap:26px;margin-top:46px;padding:32px 18px 22px}
  .foot-sub,.foot-base{grid-column:auto}
  .foot-nav a,.foot-base a{min-height:44px}
}
@media (max-width:420px){
  .hero-lede{font-size:.9rem}
  .sheet{padding:0 14px}
  .foot{padding:28px 14px 20px}
}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *{transition:none !important;animation:none !important}
}

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