:root{
  --bg:#ffffff;
  --ink:#1a1d24;
  --muted:#5c6473;
  --line:#e6e9ef;
  --accent:#3b5bdb;
  --accent-soft:#eef1fd;
  --alt:#f7f8fb;
  --pill:#eef1fd;
  --radius:14px;
  --maxw:1080px;
  --serif:"Iowan Old Style",Georgia,"Times New Roman",serif;
  --sans:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;background:var(--bg);color:var(--ink);
  font-family:var(--sans);font-size:17px;line-height:1.62;-webkit-font-smoothing:antialiased;
}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.wrap.narrow{max-width:780px}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
sup{font-size:.62em}

/* ---------- HERO ---------- */
.hero{
  background:radial-gradient(1200px 500px at 50% -120px,#dfe6ff 0%,#f4f6ff 45%,#ffffff 100%);
  border-bottom:1px solid var(--line);
  padding:54px 0 46px;text-align:center;
}
.venue{
  display:inline-block;font-weight:700;letter-spacing:.08em;text-transform:uppercase;
  font-size:.74rem;color:var(--accent);background:#fff;border:1px solid #c9d3f7;
  padding:5px 13px;border-radius:999px;margin-bottom:20px;
}
.hero h1{
  font-family:var(--serif);font-weight:600;line-height:1.18;
  font-size:clamp(1.7rem,3.6vw,2.7rem);margin:.1em 0 .55em;letter-spacing:-.01em;
}
.authors{font-size:1.06rem;margin-bottom:6px}
.authors a{color:var(--ink);font-weight:600}
.affil{color:var(--muted);font-size:.9rem;margin-bottom:24px}
.links{display:flex;gap:10px;justify-content:center;flex-wrap:wrap}
.btn{
  display:inline-block;background:var(--ink);color:#fff;padding:9px 18px;border-radius:999px;
  font-weight:600;font-size:.92rem;border:1px solid var(--ink);transition:transform .12s ease,opacity .12s;
}
.btn:hover{text-decoration:none;transform:translateY(-1px);opacity:.92}
.btn.big{padding:12px 24px;font-size:1rem}
.btn.small{background:#fff;color:var(--accent);border:1px solid #c9d3f7;padding:5px 12px;font-size:.82rem}

/* ---------- SECTIONS ---------- */
section{padding:58px 0;border-bottom:1px solid var(--line)}
section.alt{background:var(--alt)}
.band{background:var(--accent-soft);padding:34px 0;border-bottom:1px solid var(--line)}
h2{
  font-family:var(--serif);font-weight:600;font-size:clamp(1.4rem,2.6vw,2rem);
  margin:0 0 14px;letter-spacing:-.01em;display:flex;align-items:baseline;gap:.5em;
}
.num{
  display:inline-flex;align-items:center;justify-content:center;
  width:1.5em;height:1.5em;font-size:.72em;font-family:var(--sans);font-weight:700;
  color:#fff;background:var(--accent);border-radius:50%;flex:0 0 auto;
}
.sec-intro{color:var(--muted);max-width:760px;margin:0 0 26px;font-size:1.02rem}
.lede{font-size:1.12rem;line-height:1.6;margin:0}
.lede strong{color:var(--accent)}

/* ---------- TL;DR + SETUP SCHEMATIC ---------- */
.tldr-grid{display:grid;grid-template-columns:1fr 1fr;gap:30px;align-items:center}
.setup-fig{margin:0}
.setup-svg{width:100%;height:auto;display:block}
.setup-cite{text-align:center;color:var(--muted);font-size:.78rem;margin-top:6px}
.sv-lbl{fill:var(--ink);font:600 13px var(--sans)}
.sv-lbl.sv-it{font-style:italic;font-weight:500}
.sv-sub{fill:var(--muted);font:11px var(--sans)}
.sv-sub.sv-o{fill:#b5532a;font-weight:600}
.sv-sub.sv-p{fill:#7a3a8f;font-weight:600}
.sv-chip{fill:#fff;font:700 12px var(--sans)}
.sv-tag{fill:var(--ink);font:700 10px var(--sans);text-anchor:start}
.sv-tag.sv-o{fill:#b5532a}
.sv-tag.sv-p{fill:#7a3a8f}
.db ellipse,.db path{stroke:var(--ink);stroke-width:2.4;fill:none}
.db>ellipse:first-of-type{fill:#fff}
.sv-arrow{stroke:#9aa3bd;stroke-width:2;fill:none}
.sv-path{fill:none;stroke-width:2.6;stroke-linecap:round}
.sv-pathO{stroke:#b5532a}
.sv-pathP{stroke:#7a3a8f}
.sv-frame{fill:#fff;stroke-width:2.5}
.sv-frame.sv-fo{stroke:#b5532a}
.sv-frame.sv-fp{stroke:#7a3a8f}
.seed-dot{filter:drop-shadow(0 0 3px rgba(0,0,0,.25))}
@media(prefers-reduced-motion:reduce){.seed-dot{display:none}}
.takeaway{margin-top:20px;padding:14px 18px;background:var(--accent-soft);border-radius:12px;font-size:.98rem}
.note{font-size:.85rem;color:var(--muted)}
.lead-explore{margin-top:30px}

/* ---------- LINEAR INTUITION FLOW DIAGRAM ---------- */
.flow-diagram{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:24px 22px 18px;margin:6px 0 8px;box-shadow:0 6px 28px rgba(30,40,80,.06);
}
.flow{display:flex;align-items:stretch;gap:10px;flex-wrap:nowrap}
.flow-stage{
  flex:1 1 0;min-width:0;position:relative;border:1px solid var(--line);border-radius:12px;
  padding:16px 16px 14px;background:var(--alt);display:flex;flex-direction:column;gap:8px;
}
.flow-stage.stage-obs{background:#eaf6ec;border-color:#bfe0c4;flex:1.5 1 0}
.stage-title{font-weight:700;font-size:1rem;line-height:1.25}
.stage-sub{margin:0;color:var(--muted);font-size:.86rem;line-height:1.4}
.stage-math{font-size:1.15rem;margin-top:auto}
.stage-eq{font-size:.82rem;overflow-x:auto}
.stage-eq .katex-display{margin:.35em 0}
.flow-arrow{display:flex;align-items:center;color:var(--accent);font-size:1.7rem;font-weight:700;flex:0 0 auto}
.stable-badge{
  position:absolute;top:-11px;right:12px;background:#2f9e44;color:#fff;font-weight:700;
  font-size:.7rem;letter-spacing:.03em;text-transform:uppercase;padding:3px 10px;border-radius:999px;
}
.db-flow{display:flex;align-items:center;gap:14px;margin-top:4px}
.db-icon{width:46px;height:54px;flex:0 0 auto}
.db-icon ellipse,.db-icon path{stroke:var(--ink);stroke-width:2.4;fill:none}
.db-icon>ellipse:first-of-type{fill:#fff}
.dm-chips{display:flex;flex-direction:column;gap:8px}
.chip{display:inline-block;color:#fff;font-weight:700;font-size:.84rem;padding:5px 12px;border-radius:7px;text-align:center}
.chip-dm1{background:#b5532a}
.chip-dm2{background:#7a3a8f}
.flow-caption{margin:18px 2px 0;color:var(--muted);font-size:.95rem;line-height:1.55}
.flow-caption strong{color:var(--ink)}

/* ---------- COLLAPSIBLE COUNTERFACTUAL ---------- */
.cf-details{
  margin-top:22px;border:1px solid #e7c9c9;border-radius:12px;background:#fdf6f6;overflow:hidden;
}
.cf-details summary{
  cursor:pointer;list-style:none;padding:14px 18px;font-size:1.02rem;font-weight:600;color:#b0413a;
  display:flex;align-items:center;gap:10px;user-select:none;
}
.cf-details summary::-webkit-details-marker{display:none}
.cf-details summary strong{color:#8d2f2a}
.cf-chevron{display:inline-block;transition:transform .18s ease;color:#c0524a}
.cf-details[open] .cf-chevron{transform:rotate(90deg)}
.cf-body{padding:4px 20px 20px;border-top:1px solid #f0dcdc}
.cf-body p{font-size:.98rem;line-height:1.6}
.cf-fig{margin:18px 0;text-align:center}
.cf-fig img{max-width:100%;height:auto;border:1px solid var(--line);border-radius:8px;background:#fff}
.cf-note{background:#fff;border-left:3px solid #c0524a;padding:10px 14px;border-radius:8px;font-size:.95rem}

/* ---------- EXPLORER CARD ---------- */
.explorer-card{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:0 6px 28px rgba(30,40,80,.06);overflow:hidden;
}
.controls{
  display:flex;gap:24px;align-items:center;flex-wrap:wrap;
  padding:16px 20px;background:var(--alt);border-bottom:1px solid var(--line);
}
.controls label{font-weight:600;font-size:.92rem;display:flex;gap:8px;align-items:center}
select{
  font:inherit;padding:7px 12px;border:1px solid #c9d3f7;border-radius:8px;background:#fff;color:var(--ink);
}
.seed-control{display:flex;align-items:center;gap:10px;font-weight:600;font-size:.92rem}
.seed-control button{
  width:30px;height:30px;border-radius:50%;border:1px solid #c9d3f7;background:#fff;color:var(--accent);
  font-size:1.1rem;cursor:pointer;line-height:1;
}
.seed-control button:hover{background:var(--accent-soft)}
input[type=range]{accent-color:var(--accent);cursor:pointer;width:170px}
.pill{background:var(--pill);color:var(--accent);font-weight:700;padding:2px 11px;border-radius:999px;font-size:.86rem;min-width:2.4em;text-align:center}
.explorer-fig{margin:0;padding:18px;text-align:center}
.explorer-fig img{max-width:100%;height:auto;border-radius:8px}

/* split toggle */
.toggle{display:inline-flex;border:1px solid #c9d3f7;border-radius:999px;overflow:hidden;background:#fff}
.toggle button{
  font:inherit;font-weight:600;font-size:.85rem;border:none;background:#fff;color:var(--muted);
  padding:7px 14px;cursor:pointer;border-left:1px solid #e6e9ef;
}
.toggle button:first-child{border-left:none}
.toggle button.active{background:var(--accent);color:#fff}
.split-row{display:flex;gap:16px;justify-content:center;align-items:flex-start;flex-wrap:wrap}
.split-col{flex:0 1 auto;max-width:100%}
.split-col img{display:block;max-width:100%;height:auto;border-radius:8px}
.split-tag{display:block;font-size:.8rem;font-weight:700;color:var(--accent);margin-bottom:6px;text-transform:uppercase;letter-spacing:.04em}
.split-row.single .split-tag{display:none}
figcaption{color:var(--muted);font-size:.88rem;margin-top:10px;line-height:1.5}

/* ---------- KAPPA WIDGET ---------- */
.kappa-grid{display:grid;grid-template-columns:1fr 1fr;gap:34px;align-items:start}
.kappa-plot-wrap{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:16px;
  box-shadow:0 6px 28px rgba(30,40,80,.06);
}
#kappa-svg{width:100%;height:auto;display:block}
.kappa-controls{margin-top:8px;padding:0 6px}
.kappa-controls input[type=range]{width:100%}
.kappa-controls .hint{color:var(--muted);font-size:.84rem;margin-top:4px}
.kappa-text p{margin:.2em 0 1em}
.kappa-text img{max-width:100%;border-radius:8px;border:1px solid var(--line)}

/* svg styling */
.axis{stroke:#b8bfce;stroke-width:1}
.grid{stroke:#eef0f5;stroke-width:1}
.tick-lbl{fill:var(--muted);font:11px var(--sans)}
.axis-lbl{fill:var(--ink);font:13px var(--sans);font-weight:600}
.kline{fill:none;stroke-width:2.4}
.idline{fill:none;stroke:#b8bfce;stroke-dasharray:4 4;stroke-width:1.4}
.klabel{font:11px var(--sans);font-weight:700}

/* ---------- EQUATIONS ---------- */
.eq-card{
  background:#fff;border:1px solid var(--line);border-left:4px solid var(--accent);
  border-radius:10px;padding:14px 22px 6px;margin:16px 0;box-shadow:0 3px 14px rgba(30,40,80,.04);
  overflow-x:auto;
}
.eq-label{font-weight:700;color:var(--accent);font-size:.82rem;text-transform:uppercase;letter-spacing:.04em;margin-bottom:2px}
.eq-card p{color:var(--muted);font-size:.95rem;margin:.2em 0 .8em}

/* ---------- FIGURES ---------- */
.full-fig{margin:0 0 28px;text-align:center}
.full-fig img{max-width:100%;height:auto;border:1px solid var(--line);border-radius:10px}

/* ---------- CITATION ---------- */
.bibtex{position:relative}
#copy-bib{position:absolute;top:12px;right:12px}
pre{
  background:#0f1320;color:#e7ecf6;padding:20px;border-radius:12px;overflow-x:auto;
  font:13px/1.55 ui-monospace,SFMono-Regular,Menlo,monospace;
}
footer{padding:30px 0;background:#fff;color:var(--muted);font-size:.86rem;text-align:center;border:none}

/* ---------- RESPONSIVE ---------- */
@media(max-width:760px){
  body{font-size:16px}
  .kappa-grid{grid-template-columns:1fr;gap:22px}
  .controls{gap:14px}
  input[type=range]{width:130px}
  section{padding:42px 0}
  .flow{flex-direction:column}
  .flow-arrow{justify-content:center;transform:rotate(90deg)}
  .flow-stage.stage-obs{flex:1 1 auto}
  .tldr-grid{grid-template-columns:1fr;gap:18px}
  .lede{text-align:left}
}