/* =====================================================================
 *  Chaos in the Text · Trident — project page styles
 *  Colours mirror the paper: Text = blue, Image = orange, Fused = pink.
 * ===================================================================== */
:root {
  --bg: #ffffff;
  --bg-alt: #f6f7fb;
  --card: #ffffff;
  --ink: #161a23;
  --ink-2: #444b5a;
  --ink-3: #7a8191;
  --line: #e4e7ef;
  --accent: #5b3fd1;          /* Trident purple */
  --accent-soft: #efebff;
  --c-text: #3d8bd8;
  --c-image: #ef9a2a;
  --c-fused: #e47a8a;
  --c-neg: #8a90a0;
  --good: #1f9d6b;
  --bad: #d9443b;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(16,24,40,.04), 0 6px 24px rgba(16,24,40,.06);
  --serif: "Source Serif 4", Georgia, serif;
  --sans: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "JetBrains Mono", ui-monospace, monospace;
  --nav-h: 56px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1117; --bg-alt: #151823; --card: #1a1e2b;
    --ink: #eef0f6; --ink-2: #b8bdcb; --ink-3: #868c9c; --line: #2a2f3e;
    --accent: #a08bff; --accent-soft: #241f3d;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 28px rgba(0,0,0,.35);
  }
  .ph-wrap img { background: #fff; }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--nav-h) + 12px); }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 16px/1.7 var(--sans); -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; display: block; }
b, strong { font-weight: 650; }
.container { max-width: 1120px; margin: 0 auto; padding: 0 16px; }
@media (min-width: 700px) { .container { padding: 0 24px; } }
body { overflow-x: hidden; }
.container.narrow { max-width: 860px; }

/* ---------- NAV ---------- */
.nav {
  position: sticky; top: 0; z-index: 50; height: var(--nav-h);
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: saturate(160%) blur(12px); border-bottom: 1px solid var(--line);
}
.nav-inner { max-width: 1120px; margin: 0 auto; padding: 0 24px; height: 100%; display: flex; align-items: center; justify-content: space-between; }
.nav-brand { font-weight: 700; color: var(--ink); letter-spacing: -.01em; }
.nav-brand:hover { text-decoration: none; }
.nav-links { display: flex; gap: 4px; }
.nav-links a { color: var(--ink-2); font-size: 14px; font-weight: 500; padding: 6px 10px; border-radius: 8px; }
.nav-links a:hover, .nav-links a.active { color: var(--accent); background: var(--accent-soft); text-decoration: none; }
.nav-toggle { display: none; background: none; border: 0; font-size: 22px; color: var(--ink); cursor: pointer; }
.nav-progress { position: absolute; left: 0; bottom: -1px; height: 2px; width: 0; background: linear-gradient(90deg, var(--c-text), var(--accent), var(--c-image)); }
@media (max-width: 860px) {
  .nav-toggle { display: block; }
  .nav-links { display: none; position: absolute; top: var(--nav-h); left: 0; right: 0; flex-direction: column;
    background: var(--bg); border-bottom: 1px solid var(--line); padding: 8px 16px 16px; }
  .nav-links.open { display: flex; }
}

/* ---------- HERO ---------- */
.hero { position: relative; padding: 72px 0 40px; text-align: center; overflow: hidden; }
.hero-bg {
  position: absolute; inset: -40% -10% auto -10%; height: 120%; z-index: -1; opacity: .55;
  background:
    radial-gradient(40% 50% at 20% 30%, color-mix(in srgb, var(--c-text) 22%, transparent), transparent 70%),
    radial-gradient(35% 45% at 80% 25%, color-mix(in srgb, var(--c-image) 22%, transparent), transparent 70%),
    radial-gradient(30% 40% at 50% 60%, color-mix(in srgb, var(--accent) 16%, transparent), transparent 70%);
}
.venue-badge {
  display: inline-block; font-size: 13px; font-weight: 600; letter-spacing: .04em; text-transform: uppercase;
  color: var(--accent); background: var(--accent-soft); padding: 4px 12px; border-radius: 99px; margin-bottom: 18px;
}
.title { margin: 0 0 26px; font-family: var(--serif); font-weight: 700; line-height: 1.12; letter-spacing: -.015em; }
.title-hook {
  display: block; font-size: clamp(40px, 7vw, 72px);
  background: linear-gradient(95deg, var(--c-text) 0%, var(--accent) 50%, var(--c-image) 100%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.title-sub { display: block; font-size: clamp(20px, 3vw, 30px); color: var(--ink); font-weight: 600; margin-top: 10px; }
.authors { display: flex; flex-wrap: wrap; justify-content: center; gap: 4px 22px; font-size: 18px; }
.author a { color: var(--ink); font-weight: 500; }
.author sup, .affils sup, .affil-notes sup { color: var(--ink-3); font-size: 11px; }
.affils {
  margin-top: 6px; color: var(--ink-2);
  display: flex; justify-content: center; flex-wrap: wrap;
  gap: 4px 22px;              /* 行间距 4px，列间距 22px */
}
.affil-break { flex-basis: 100%; height: 0; }   /* 强制换行 */
.affil-notes { font-size: 13px; color: var(--ink-3); margin-top: 4px; }
.link-buttons { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; margin: 26px 0 28px; }
.btn {
  display: inline-flex; align-items: center; gap: 8px; padding: 9px 18px; border-radius: 99px;
  background: var(--ink); color: var(--bg); font-weight: 600; font-size: 15px; transition: transform .15s, box-shadow .15s;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); box-shadow: 0 6px 18px rgba(0,0,0,.18); }
.btn svg { width: 17px; height: 17px; }
.btn-ico { font-size: 15px; line-height: 1; }
.hero-abstract { font-size: 17.5px; color: var(--ink-2); text-align: left; margin: 0 auto 36px; }
.hero-abstract em { font-style: normal; font-weight: 650; color: var(--bad); }

.teaser { margin: 0; padding: 18px; }
.teaser-video { width: 100%; border-radius: 10px; display: block; }
.teaser figcaption { text-align: left; }

/* ---------- SECTIONS ---------- */
.section { padding: 84px 0; }
.section.alt { background: var(--bg-alt); }
.eyebrow { font-size: 13px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); margin-bottom: 8px; }
.section-title { font-family: var(--serif); font-size: clamp(28px, 4vw, 40px); line-height: 1.2; margin: 0 0 18px; letter-spacing: -.01em; }
.section-title .hl { color: var(--accent); }
.sub-title { font-family: var(--serif); font-size: 24px; margin: 40px 0 10px; }
.lead { font-size: 18px; color: var(--ink-2); max-width: 900px; margin-bottom: 30px; }
.small { font-size: 14px; color: var(--ink-3); }
.caption, figcaption { font-size: 14px; color: var(--ink-3); margin-top: 12px; line-height: 1.6; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
figure.card { padding: 18px; margin: 0 0 28px; }

.tag { display: inline-block; font-size: .82em; font-weight: 600; padding: 1px 9px; border-radius: 99px; line-height: 1.6; white-space: nowrap; }
.t-text  { --c: var(--c-text); }
.t-image { --c: var(--c-image); }
.t-fused { --c: var(--c-fused); }
.t-neg   { --c: var(--c-neg); }
.tag.t-text, .tag.t-image, .tag.t-fused { color: var(--c); background: color-mix(in srgb, var(--c) 14%, transparent); }

/* ---------- TL;DR ---------- */
.tldr-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 26px; }
.tldr-card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; box-shadow: var(--shadow); display: flex; flex-direction: column; }
.tldr-card.accent { border-color: color-mix(in srgb, var(--accent) 45%, var(--line)); background: linear-gradient(180deg, var(--accent-soft), var(--card) 60%); }
.tldr-num { font-family: var(--mono); font-size: 13px; color: var(--ink-3); }
.tldr-card h3 { font-size: 19px; margin: 6px 0 8px; line-height: 1.3; }
.tldr-card p { color: var(--ink-2); font-size: 15px; margin: 0 0 18px; flex: 1; }
.tldr-stat { display: flex; align-items: baseline; flex-wrap: wrap; gap: 6px 10px; border-top: 1px dashed var(--line); padding-top: 14px; }
.tldr-stat .big { font-size: 30px; font-weight: 800; letter-spacing: -.02em; font-variant-numeric: tabular-nums; }
.tldr-stat .arrow { color: var(--ink-3); font-size: 20px; }
.tldr-stat .cap { width: 100%; font-size: 13px; color: var(--ink-3); }
.good { color: var(--good); } .bad { color: var(--bad); }
@media (max-width: 860px) { .tldr-grid { grid-template-columns: 1fr; } }

/* ---------- WIDGETS ---------- */
.widget { padding: 22px 24px; margin: 26px 0; }
.widget-head { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 10px; margin-bottom: 14px; }
.widget-head h3 { margin: 0; font-size: 18px; }
.widget-note { font-size: 13px; color: var(--ink-3); }
.widget-note.warn { color: #b26a00; background: #fff4e0; padding: 2px 10px; border-radius: 99px; }
@media (prefers-color-scheme: dark) { .widget-note.warn { background: #3a2a10; color: #ffbf66; } }
.plot { width: 100%; min-height: 340px; }
.plot-3d { min-height: 520px; }
.controls { display: flex; flex-wrap: wrap; gap: 14px; align-items: center; margin-bottom: 8px; }
.controls.compact { margin: 0; }
.controls label { font-size: 13px; color: var(--ink-3); display: flex; align-items: center; gap: 8px; }
select {
  font: inherit; font-size: 14px; color: var(--ink); background: var(--bg); border: 1px solid var(--line);
  border-radius: 8px; padding: 5px 10px;
}
.seg { display: inline-flex; background: var(--bg-alt); border: 1px solid var(--line); border-radius: 10px; padding: 3px; }
.seg button { font: inherit; font-size: 13px; font-weight: 500; border: 0; background: none; color: var(--ink-2); padding: 5px 12px; border-radius: 7px; cursor: pointer; }
.seg button.active { background: var(--card); color: var(--accent); box-shadow: 0 1px 3px rgba(0,0,0,.08); font-weight: 600; }
.btn-sm { font: inherit; font-size: 13px; font-weight: 600; border: 1px solid var(--line); background: var(--card); color: var(--ink); padding: 6px 14px; border-radius: 8px; cursor: pointer; }
.btn-sm:hover { border-color: var(--accent); color: var(--accent); }
.btn-sm.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-sm.primary:hover { color: #fff; filter: brightness(1.08); }

/* V-curve widget */
.vcurve-grid { display: grid; grid-template-columns: 340px 1fr; gap: 26px; align-items: center; }
.corpus-grid { display: grid; grid-template-columns: repeat(10, 1fr); gap: 5px; margin-bottom: 16px; }
.doc {
  aspect-ratio: 3/4; border-radius: 4px; position: relative; overflow: hidden;
  transition: background .35s, transform .35s; background: var(--c-image);
}
.doc::after { content: ""; position: absolute; inset: 22% 18%; border-radius: 2px; transition: all .35s;
  background: repeating-linear-gradient(90deg, rgba(255,255,255,.85) 0 18%, transparent 18% 26%); opacity: .0; }
.doc.img::before { content: ""; position: absolute; left: 18%; right: 18%; bottom: 20%; height: 40%;
  background: linear-gradient(90deg, rgba(255,255,255,.85) 0 20%, transparent 20% 40%, rgba(255,255,255,.85) 40% 60%, transparent 60% 80%, rgba(255,255,255,.85) 80%);
  clip-path: polygon(0 60%, 20% 60%, 20% 100%, 40% 100%, 40% 20%, 60% 20%, 60% 100%, 80% 100%, 80% 0, 100% 0, 100% 100%, 0 100%); }
.doc.txt { background: var(--c-text); transform: rotateY(180deg); }
.doc.txt::after { opacity: 1; background: repeating-linear-gradient(180deg, rgba(255,255,255,.85) 0 2px, transparent 2px 6px); }
.slider-row { display: flex; align-items: center; gap: 10px; }
input[type=range] { flex: 1; accent-color: var(--accent); }
.readout { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; margin: 14px 0; }
.readout > div, .pg-metrics > div { background: var(--bg-alt); border-radius: 10px; padding: 8px 10px; }
.ro-label { display: block; font-size: 11.5px; color: var(--ink-3); text-transform: uppercase; letter-spacing: .04em; }
.ro-val { font-weight: 700; font-size: 17px; font-variant-numeric: tabular-nums; }
@media (max-width: 860px) { .vcurve-grid { grid-template-columns: 1fr; } }

.vcurve-grid > div { min-width: 0; }
.vcurve-grid .plot { width: 100%; }
.vcurve-grid .plot svg { width: 100%; height: auto; display: block; overflow: visible; }

/* static figure blocks */
.static-figs { margin: 18px 0 28px; }
.static-figs summary { cursor: pointer; font-weight: 600; color: var(--ink-2); font-size: 15px; padding: 8px 0; }
.static-figs summary:hover { color: var(--accent); }
.static-figs .ph-wrap { margin: 12px 0; }
.two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 20px 0; }
@media (max-width: 760px) { .two-col { grid-template-columns: 1fr; } }

/* placeholder for missing images */
.ph-wrap { position: relative; }
.ph-wrap img { border-radius: 8px; width: 100%; }
.ph-box {
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 6px; text-align: center;
  min-height: 220px; border: 2px dashed color-mix(in srgb, var(--accent) 40%, var(--line)); border-radius: 10px;
  background: repeating-linear-gradient(45deg, var(--bg-alt) 0 12px, var(--card) 12px 24px); color: var(--ink-2); padding: 20px;
}
.ph-box .ph-title { font-weight: 700; color: var(--accent); }
.ph-box code { font-family: var(--mono); font-size: 12.5px; color: var(--ink-3); }

/* split layouts */
.split { display: grid; grid-template-columns: 1fr 1.2fr; gap: 36px; align-items: center; margin: 36px 0; }
.split-fig { margin: 0; }
.split-text .sub-title { margin-top: 0; }
@media (max-width: 860px) { .split { grid-template-columns: minmax(0, 1fr); } }
.split > * { min-width: 0; }
.ph-box code { word-break: break-all; }

.callout { border-left: 4px solid var(--accent); background: var(--accent-soft); padding: 14px 18px; border-radius: 0 10px 10px 0; color: var(--ink); margin: 20px 0; }
.callout.neutral { border-left-color: var(--c-text); background: color-mix(in srgb, var(--c-text) 9%, var(--card)); }
.mini-card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px 22px; }
.mini-card h4 { margin: 0 0 6px; font-size: 16px; }
.mini-card p { margin: 0; color: var(--ink-2); font-size: 15px; }

/* ---------- METHOD ---------- */
.method-steps { display: grid; gap: 18px; margin: 30px 0; }
.step > div { min-width: 0; }
@media (max-width: 600px) { .step { grid-template-columns: 1fr !important; padding: 18px !important; } .eq { font-size: 14px; } }
.step { display: grid; grid-template-columns: 44px minmax(0, 1fr); gap: 18px; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; }
.step-num { width: 40px; height: 40px; border-radius: 50%; background: var(--accent); color: #fff; display: grid; place-items: center; font-weight: 800; }
.step h4 { margin: 4px 0 6px; font-size: 18px; }
.step p { margin: 6px 0; color: var(--ink-2); }
.eq { overflow-x: auto; overflow-y: hidden; padding: 4px 0; position: relative; }
.eq-hl { background: var(--accent-soft); border-radius: 10px; padding: 8px 12px; margin: 10px 0; }
.math { font-family: var(--serif); font-style: italic; }

/* loss playground */
.pg-grid { display: grid; grid-template-columns: 320px 1fr; gap: 28px; }
.pg-group-title { font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .05em; color: var(--ink-3); margin: 10px 0 4px; }
.pg-slider { display: block; font-size: 13.5px; font-weight: 600; color: var(--c, var(--ink-2)); margin: 6px 0; }
.pg-slider span { float: right; font-family: var(--mono); font-weight: 500; color: var(--ink-2); }
.pg-slider input { width: 100%; accent-color: var(--c, var(--accent)); }
.pg-buttons { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.pg-bars { display: grid; grid-template-columns: repeat(5, 1fr); gap: 14px; align-items: end; height: 220px; border-bottom: 1px solid var(--line); padding: 0 6px; }
.pg-bar { display: flex; flex-direction: column; align-items: center; justify-content: flex-end; height: 100%; position: relative; }
.pg-bar .fill { width: 70%; border-radius: 6px 6px 0 0; background: var(--c); transition: height .25s; min-height: 2px; }
.pg-bar .pv { font-family: var(--mono); font-size: 12.5px; margin-bottom: 4px; }
.pg-bar .grad { position: absolute; top: 0; font-size: 18px; font-weight: 800; }
.pg-bar .grad.up { color: var(--good); } .pg-bar .grad.down { color: var(--bad); }
.pg-labels { display: grid; grid-template-columns: repeat(5, 1fr); gap: 14px; padding: 6px 6px 0; text-align: center; font-size: 12px; color: var(--ink-3); }
.pg-bar.pos .fill { box-shadow: inset 0 0 0 2px rgba(255,255,255,.35); }
.pg-uniform { position: absolute; left: 0; right: 0; border-top: 1px dashed var(--ink-3); pointer-events: none; }
.pg-metrics { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin: 16px 0 10px; }
.pg-rank { font-size: 13.5px; color: var(--ink-2); }
.pg-rank ol { margin: 4px 0 0; padding-left: 20px; }
.pg-rank .rk-pos { font-weight: 600; }
@media (max-width: 860px) { .pg-grid { grid-template-columns: 1fr; } .pg-metrics { grid-template-columns: repeat(2, 1fr); } }

/* ---------- RESULTS ---------- */
.kpi-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin: 20px 0 10px; }
.kpi { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px; text-align: center; box-shadow: var(--shadow); }
.kpi-val { font-size: 34px; font-weight: 800; letter-spacing: -.02em; }
.kpi-lab { font-size: 13.5px; color: var(--ink-2); line-height: 1.45; }
.kpi-lab small { color: var(--ink-3); font-family: var(--mono); font-size: 12px; }
@media (max-width: 860px) { .kpi-row { grid-template-columns: repeat(2, 1fr); } }

.table-wrap { overflow-x: auto; }
table.res { border-collapse: collapse; width: 100%; font-size: 13.5px; font-variant-numeric: tabular-nums; }
table.res th, table.res td { padding: 6px 9px; text-align: center; white-space: nowrap; }
table.res thead th { font-weight: 700; border-bottom: 1px solid var(--line); }
table.res thead tr:first-child th { border-bottom: 0; }
table.res thead tr.sub th { font-weight: 500; color: var(--ink-3); font-size: 12px; }
table.res td:first-child, table.res th:first-child { text-align: left; position: sticky; left: 0; background: var(--card); z-index: 1; }
table.res tr.grp td { background: var(--bg-alt); font-style: italic; color: var(--ink-3); text-align: center !important; font-size: 12.5px; }
table.res tr.subrow td:first-child { padding-left: 24px; color: var(--ink-2); }
table.res tr.ours td { background: var(--accent-soft); }
table.res tr.ours td:first-child { background: var(--accent-soft); font-weight: 700; color: var(--accent); }
table.res tr.abl td { font-style: italic; color: var(--ink-3); }
table.res tr.abl td:first-child { padding-left: 24px; }
table.res tbody tr:hover td { background: color-mix(in srgb, var(--c-text) 10%, var(--card)); }
table.res td.best { font-weight: 800; }
table.res td.second { text-decoration: underline; text-underline-offset: 3px; }
table.res td.avg, table.res th.avg { border-left: 1px solid var(--line); }
table.res .delta { display: block; font-size: 10.5px; font-weight: 600; }

.compare-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; margin: 18px 0; }
.compare-grid figure { margin: 0; }
@media (max-width: 760px) { .compare-grid { grid-template-columns: 1fr; } }
.compare { position: relative; overflow: hidden; border-radius: 12px; border: 1px solid var(--line); background: #fff; user-select: none; touch-action: none; aspect-ratio: 4/3; }
.compare .layer { position: absolute; inset: 0; }
.compare .layer img, .compare .layer .ph-box { width: 100%; height: 100%; object-fit: contain; border-radius: 0; }
.compare .layer.after { clip-path: inset(0 0 0 50%); }
.compare .handle { position: absolute; top: 0; bottom: 0; left: 50%; width: 3px; background: var(--accent); transform: translateX(-50%); cursor: ew-resize; }
.compare .handle::after { content: "⇆"; position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); width: 36px; height: 36px; border-radius: 50%;
  background: var(--accent); color: #fff; display: grid; place-items: center; font-size: 16px; box-shadow: 0 2px 10px rgba(0,0,0,.25); }
.compare .lbl { position: absolute; top: 10px; font-size: 12px; font-weight: 700; padding: 3px 10px; border-radius: 99px; background: rgba(0,0,0,.65); color: #fff; z-index: 2; }
.compare .lbl.l { left: 10px; } .compare .lbl.r { right: 10px; background: var(--accent); }

/* ---------- ANALYSIS ---------- */
.sigma-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 16px 0 4px; }
.sigma { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 12px 14px; }
.sigma-model { display: block; font-size: 13px; color: var(--ink-3); }
.sigma-vals { font-size: 20px; font-variant-numeric: tabular-nums; }
.sigma-vals s { color: var(--ink-3); }
.sigma-vals b { color: var(--good); }
.ablation-grid { display: flex; align-items: stretch; gap: 10px; flex-wrap: wrap; margin: 18px 0; }
.abl { flex: 1 1 170px; background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 14px; text-align: center; }
.abl.ours { border-color: var(--accent); background: var(--accent-soft); }
.abl.dim { opacity: .65; }
.abl-name { font-weight: 650; font-size: 14.5px; line-height: 1.35; min-height: 40px; }
.abl-name small { font-weight: 400; color: var(--ink-3); }
.abl-sigma { font-family: var(--mono); font-size: 14px; margin-top: 8px; }
.abl-ndcg { font-size: 13px; color: var(--ink-2); }
.abl-arrow { align-self: center; color: var(--ink-3); font-size: 20px; }
.abl-arrow.dim { opacity: .5; }
@media (max-width: 860px) { .abl-arrow { display: none; } }

/* ---------- Q&A ---------- */
.qa { display: grid; gap: 10px; margin-top: 20px; }
.qa-item { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 0 20px; }
.qa-item summary { cursor: pointer; list-style: none; padding: 16px 0; font-weight: 650; display: flex; gap: 12px; align-items: flex-start; }
.qa-item summary::-webkit-details-marker { display: none; }
.qa-item summary::after { content: "+"; margin-left: auto; color: var(--ink-3); font-size: 20px; line-height: 1; transition: transform .2s; }
.qa-item[open] summary::after { transform: rotate(45deg); }
.qa-q { flex: none; width: 24px; height: 24px; border-radius: 6px; background: var(--accent); color: #fff; font-size: 13px; display: grid; place-items: center; }
.qa-a { padding: 0 0 18px 36px; color: var(--ink-2); }

/* ---------- BIBTEX ---------- */
.bibtex { position: relative; padding: 0; }
.bibtex pre { margin: 0; padding: 22px; overflow-x: auto; font: 13.5px/1.6 var(--mono); color: var(--ink); }
.copy-btn { position: absolute; top: 12px; right: 12px; font: 600 12px var(--sans); border: 1px solid var(--line); background: var(--bg-alt); color: var(--ink-2); padding: 5px 12px; border-radius: 7px; cursor: pointer; }
.copy-btn:hover { color: var(--accent); border-color: var(--accent); }

.footer { padding: 36px 0 50px; text-align: center; font-size: 13.5px; color: var(--ink-3); border-top: 1px solid var(--line); }
.to-top { position: fixed; right: 20px; bottom: 20px; width: 42px; height: 42px; border-radius: 50%; border: 0; background: var(--accent); color: #fff; font-size: 18px;
  cursor: pointer; opacity: 0; pointer-events: none; transition: opacity .2s; box-shadow: var(--shadow); }
.to-top.show { opacity: 1; pointer-events: auto; }

/* reveal on scroll */
.reveal { opacity: 0; transform: translateY(16px); transition: opacity .6s ease, transform .6s ease; }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) { .reveal { opacity: 1; transform: none; transition: none; } html { scroll-behavior: auto; } }