:root{
  --ink:#0E2723;
  --ink-dim:#4C6560;
  --ink-faint:#84948F;
  --bg:#F6F8F4;
  --bg-raised:#FFFFFF;
  --bg-card:#FFFFFF;
  --line:#DEE6DF;
  --teal:#0891B2;
  --teal-bright:#0BA8C0;
  --teal-wash:#E6F4F4;
  --amber:#B5680A;
  --amber-wash:#FCEBCB;
  --rose:#C0413B;
  --font-display:'Source Serif 4','Iowan Old Style',ui-serif,Georgia,serif;
  --font-body:'IBM Plex Sans',system-ui,-apple-system,sans-serif;
  --font-mono:'IBM Plex Mono',ui-monospace,'SF Mono',monospace;
}
*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  background:
    radial-gradient(1100px 560px at 10% -12%, rgba(8,145,178,0.06), transparent 60%),
    radial-gradient(900px 480px at 100% 0%, rgba(181,104,10,0.045), transparent 55%),
    var(--bg);
  color:var(--ink);
  font-family:var(--font-body);
  -webkit-font-smoothing:antialiased;
}
a{color:inherit;}
::selection{background:var(--teal);color:#fff;}

a:focus-visible, button:focus-visible, input:focus-visible{
  outline:2px solid var(--teal); outline-offset:2px;
}

@media (prefers-reduced-motion: reduce){
  *{animation-duration:0.001ms !important; transition-duration:0.001ms !important;}
}

.wrap{max-width:1040px;margin:0 auto;padding:0 24px;}

/* ---------- top strip ---------- */
.chartbar{
  border-bottom:1px solid var(--line);
  font-family:var(--font-mono);
  font-size:11px;
  letter-spacing:.08em;
  text-transform:uppercase;
  color:var(--ink-faint);
  padding:10px 0;
  background:var(--bg-raised);
}
.chartbar .wrap{display:flex;justify-content:space-between;flex-wrap:wrap;gap:8px;}
.chartbar a{color:var(--teal);text-decoration:none;border-bottom:1px dotted rgba(8,145,178,.4);}
.chartbar a:hover{color:var(--ink);}

/* ---------- hero ---------- */
header.hero{padding:76px 0 56px;position:relative;}
header.chhero{padding:48px 0 44px;}
.backlink{
  display:inline-block;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.04em;
  color:var(--ink-dim);text-decoration:none;
  margin-bottom:26px;
  border-bottom:1px dotted var(--line);
}
.backlink:hover{color:var(--teal);border-color:var(--teal);}

.eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;text-transform:uppercase;
  color:var(--teal);
  border:1px solid rgba(8,145,178,.28);
  background:var(--teal-wash);
  padding:6px 12px;border-radius:100px;
  margin-bottom:28px;
}
.eyebrow::before{content:"";width:6px;height:6px;border-radius:50%;background:var(--teal);box-shadow:0 0 0 4px rgba(8,145,178,.15);}

h1.title{
  font-family:var(--font-display);
  font-weight:600;
  font-size:clamp(2.6rem,6vw,4.6rem);
  line-height:1.02;
  margin:0 0 22px;
  letter-spacing:-0.01em;
}
.chhero h1.title{font-size:clamp(2rem,4.4vw,3.1rem);line-height:1.08;}
h1.title em{
  font-style:italic;
  color:var(--teal);
}
p.lede{
  font-size:clamp(1.05rem,1.6vw,1.25rem);
  line-height:1.6;
  color:var(--ink-dim);
  max-width:640px;
  margin:0 0 36px;
}
p.lede b{color:var(--ink);font-weight:600;}

.statrow{display:flex;gap:0;border:1px solid var(--line);border-radius:10px;overflow:hidden;max-width:640px;background:var(--bg-card);}
.chstat{max-width:340px;margin-top:8px;}
.stat{flex:1;padding:16px 18px;border-right:1px solid var(--line);}
.stat:last-child{border-right:none;}
.stat .n{font-family:var(--font-mono);font-size:1.6rem;color:var(--teal);font-weight:600;line-height:1;}
.stat .l{font-size:11px;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-faint);margin-top:6px;font-family:var(--font-mono);}

/* ---------- controls ---------- */
.controls{
  position:sticky;top:0;z-index:20;
  background:rgba(246,248,244,.88);
  backdrop-filter:blur(10px);
  border-bottom:1px solid var(--line);
  padding:14px 0;
}
.controls .row{display:flex;gap:12px;align-items:center;flex-wrap:wrap;}
.search{
  flex:1;min-width:220px;
  display:flex;align-items:center;gap:10px;
  background:var(--bg-card);
  border:1px solid var(--line);
  border-radius:8px;
  padding:10px 14px;
}
.search svg{flex:none;opacity:.5;}
.search input{
  background:none;border:none;outline:none;color:var(--ink);
  font-family:var(--font-body);font-size:15px;width:100%;
}
.search input::placeholder{color:var(--ink-faint);}
.toggles{display:flex;gap:8px;font-family:var(--font-mono);font-size:12px;}
.toggles button{
  background:var(--bg-card);border:1px solid var(--line);color:var(--ink-dim);
  padding:9px 13px;border-radius:8px;cursor:pointer;letter-spacing:.03em;
  transition:border-color .15s, color .15s, background .15s;
}
.toggles button:hover{border-color:var(--teal);color:var(--ink);}
.count{font-family:var(--font-mono);font-size:12px;color:var(--ink-faint);white-space:nowrap;}

/* ---------- subject grid ---------- */
main{padding:44px 0 100px;}
.chmain{padding-top:8px;}
.section-label{
  font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;text-transform:uppercase;
  color:var(--ink-faint);margin:0 0 18px;display:flex;align-items:center;gap:10px;
}
.section-label::after{content:"";flex:1;height:1px;background:var(--line);}

.board{display:flex;flex-direction:column;gap:12px;}

.card{
  border:1px solid var(--line);
  background:var(--bg-card);
  border-radius:12px;
  overflow:hidden;
  transition:border-color .18s, box-shadow .18s;
}
.card[data-hidden="true"]{display:none;}
.card:hover{border-color:rgba(8,145,178,.4);box-shadow:0 2px 14px rgba(14,39,35,.05);}

.card-head{
  display:grid;
  grid-template-columns:56px 1fr auto auto;
  align-items:center;
  gap:16px;
  padding:16px 20px;
  cursor:pointer;
  user-select:none;
}
.rx{
  font-family:var(--font-mono);
  font-size:12px;
  background:var(--teal-wash);
  border:1px solid rgba(8,145,178,.25);
  border-radius:6px;
  width:44px;height:44px;
  display:flex;align-items:center;justify-content:center;
  color:var(--teal);
  font-weight:600;
}
.card-title{min-width:0;}
.card-title h2{
  font-family:var(--font-display);
  font-weight:600;
  font-size:1.28rem;
  margin:0 0 3px;
  letter-spacing:-.005em;
}
.card-title .sub{
  font-family:var(--font-mono);
  font-size:11.5px;
  color:var(--ink-faint);
  letter-spacing:.03em;
  white-space:nowrap;
  overflow:hidden;
  text-overflow:ellipsis;
}
.chip{
  font-family:var(--font-mono);font-size:11px;letter-spacing:.06em;
  color:var(--ink-dim);
  border:1px solid var(--line);
  background:#FAFBF8;
  padding:5px 10px;border-radius:100px;
  white-space:nowrap;
}
.caret{
  width:20px;height:20px;color:var(--ink-faint);
  transition:transform .2s ease;
  flex:none;
}
.card.open .caret{transform:rotate(180deg);color:var(--teal);}

.card-body{
  max-height:0;
  overflow:hidden;
  transition:max-height .28s ease;
  border-top:1px solid transparent;
}
.card.open .card-body{border-top:1px solid var(--line);}

.chlist{
  display:grid;
  grid-template-columns:repeat(2,1fr);
  gap:0;
}
@media (max-width:680px){ .chlist{grid-template-columns:1fr;} }

.chitem{
  padding:13px 20px;
  border-bottom:1px solid var(--line);
  display:flex;
  gap:12px;
  align-items:baseline;
}
.chlist .chitem:nth-child(odd){border-right:1px solid var(--line);}
@media (max-width:680px){ .chlist .chitem:nth-child(odd){border-right:none;} }

.chitem.linked{
  text-decoration:none;
  transition:background .15s;
}
.chitem.linked:hover{background:var(--teal-wash);}
.chitem.linked .chtext{color:var(--ink);}
.chitem.linked .arrow{
  margin-left:auto;flex:none;color:var(--teal);opacity:0;
  transition:opacity .15s, transform .15s;
  transform:translateX(-4px);
}
.chitem.linked:hover .arrow{opacity:1;transform:translateX(0);}

.chnum{
  font-family:var(--font-mono);
  font-size:11px;
  color:var(--teal);
  flex:none;
  width:20px;
  padding-top:2px;
}
.chtext{font-size:14.5px;line-height:1.45;color:var(--ink-dim);}
.chtext mark{
  background:var(--amber-wash);
  color:var(--ink);
  border-radius:2px;
  padding:0 1px;
}

.empty{
  text-align:center;padding:60px 20px;color:var(--ink-faint);font-family:var(--font-mono);font-size:13px;
}

/* ---------- topic list (chapter pages) ---------- */
.topiclist{
  border:1px solid var(--line);
  background:var(--bg-card);
  border-radius:12px;
  overflow:hidden;
  margin-bottom:36px;
}
.topicitem{
  display:flex;gap:14px;align-items:baseline;
  padding:16px 22px;
  border-bottom:1px solid var(--line);
}
.topicitem:last-child{border-bottom:none;}
.topicitem:hover{background:var(--teal-wash);}
.topicitem .chnum{width:24px;font-size:12px;}
.topicitem .chtext{font-size:15.5px;color:var(--ink);line-height:1.55;}

.chapternav{
  display:flex;gap:10px;flex-wrap:wrap;align-items:center;justify-content:space-between;
  margin-bottom:40px;
}
.navpill{
  font-family:var(--font-mono);font-size:12px;
  border:1px solid var(--line);
  background:var(--bg-card);
  padding:10px 16px;border-radius:100px;
  text-decoration:none;color:var(--ink-dim);
  transition:border-color .15s, color .15s;
}
.navpill:hover{border-color:var(--teal);color:var(--teal);}
.navpill.disabled{color:var(--ink-faint);opacity:.5;}

/* ---------- vibe rounds tie-in strip ---------- */
.tie{
  margin-top:64px;
  border:1px solid var(--line);
  border-radius:14px;
  padding:32px 30px;
  background: linear-gradient(135deg, var(--teal-wash), #FFFFFF);
  position:relative;
}
.tie h3{
  font-family:var(--font-display);
  font-size:1.5rem;
  margin:0 0 10px;
  font-weight:600;
}
.tie p{color:var(--ink-dim);line-height:1.6;max-width:620px;margin:0 0 18px;font-size:15px;}
.tie .btnrow{display:flex;gap:12px;flex-wrap:wrap;}
.btn{
  font-family:var(--font-mono);font-size:12.5px;letter-spacing:.04em;
  padding:11px 18px;border-radius:8px;text-decoration:none;
  display:inline-flex;align-items:center;gap:8px;
}
.btn.primary{background:var(--teal);color:#fff;font-weight:600;}
.btn.primary:hover{background:var(--teal-bright);}
.btn.ghost{border:1px solid var(--line);color:var(--ink-dim);background:var(--bg-card);}
.btn.ghost:hover{border-color:var(--teal);color:var(--teal);}

footer{
  border-top:1px solid var(--line);
  padding:30px 0 60px;
  font-family:var(--font-mono);
  font-size:12px;
  color:var(--ink-faint);
}
footer .wrap{display:flex;justify-content:space-between;flex-wrap:wrap;gap:10px;}
footer a{color:var(--ink-dim);text-decoration:none;border-bottom:1px dotted var(--line);}
footer a:hover{color:var(--teal);}

.visually-hidden{position:absolute;left:-9999px;}