/* MotionPersona project page
   Palette, type and surfaces follow ui-skills.com (neutral greys, Inter Variable + JetBrains Mono, hairlines, small radii);
   motion and detail follow the apple-design skill (size-specific tracking, translucent nav, press feedback,
   reduced-motion / transparency / contrast). */

:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --band: #fafafa;
  --fill: #f5f5f5;
  --ink: #151515;
  --muted: #757575;
  --faint: #a5a5a5;
  --line: #ededed;
  --line-strong: #dcdcdc;
  --persona: #e2552d;
  --body: #2f6fde;
  --style: #7a52c8;
  --radius: 12px;
  --radius-sm: 8px;
  --nav-bg: rgba(255, 255, 255, 0.78);
  --sans: "Inter Variable", "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b0b0c;
    --band: #101012;
    --fill: #19191c;
    --ink: #ededee;
    --muted: #9a9aa2;
    --faint: #8a8a93;
    --line: #232327;
    --line-strong: #34343a;
    --persona: #ff7a55;
    --body: #6c9bff;
    --style: #a98aef;
    --nav-bg: rgba(11, 11, 12, 0.78);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 64px; -webkit-text-size-adjust: 100%; }
body {
  margin: 0; overflow-x: hidden;
  background: var(--bg); color: var(--ink);
  font: 400 16px/1.65 var(--sans);
  font-feature-settings: "cv11", "ss03", "calt";
  -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility;
}
a { color: var(--ink); text-decoration: underline; text-decoration-color: var(--line-strong); text-underline-offset: 3px; transition: text-decoration-color .15s; }
a:hover { text-decoration-color: currentColor; }
img, video { display: block; max-width: 100%; }
p { margin: 0 0 16px; }
b, strong { font-weight: 600; }
code { white-space: nowrap; font: 0.86em var(--mono); background: var(--fill); border: 1px solid var(--line); padding: 1px 6px; border-radius: 6px; }
kbd { font: 500 11.5px var(--mono); border: 1px solid var(--line-strong); border-bottom-width: 2px; border-radius: 6px; padding: 1px 6px; background: var(--bg); }

.wrap { width: min(880px, 100% - 40px); margin: 0 auto; }
.wrap.narrow { width: min(720px, 100% - 40px); }
.wrap-wide { width: min(1120px, 100% - 40px); margin: 0 auto; }
.c-persona { color: var(--persona); }
.c-body { color: var(--body); }
.c-style { color: var(--style); }
.c-persona-bg { background: var(--persona); }
.c-body-bg { background: var(--body); }

/* ---------- navigation ---------- */
.nav { position: sticky; top: 0; z-index: 20; background: var(--nav-bg);
  -webkit-backdrop-filter: saturate(180%) blur(16px); backdrop-filter: saturate(180%) blur(16px);
  box-shadow: 0 1px 0 transparent; transition: box-shadow .2s; }
.nav.stuck { box-shadow: 0 1px 0 var(--line); }
.nav-in { display: flex; align-items: center; justify-content: space-between; height: 52px; width: min(1120px, 100% - 40px); }
.brand { font-weight: 600; font-size: 15px; letter-spacing: -0.015em; text-decoration: none; }
.nav-right { display: flex; align-items: center; gap: 22px; }
.nav-links { display: flex; gap: 22px; font-size: 13.5px; }
.nav-links a { color: var(--muted); text-decoration: none; transition: color .15s; }
.nav-links a:hover { color: var(--ink); }
.nav-cta { display: inline-flex; align-items: center; padding: 6px 14px; border-radius: 10px; background: var(--ink); color: var(--bg); font-size: 13px; font-weight: 500; text-decoration: none; transition: transform .12s ease-out, opacity .15s; }
.nav-cta:hover { opacity: .85; }
.nav-cta:active { transform: scale(0.97); }

/* ---------- hero ---------- */
.hero { padding: 72px 0 56px; text-align: left; }
.eyebrow { margin: 0 0 18px; font: 500 12px var(--mono); letter-spacing: .06em; text-transform: uppercase; color: var(--muted); }
h1 { margin: 0; font-size: clamp(38px, 5.6vw, 56px); line-height: 1.05; letter-spacing: -0.035em; font-weight: 600; }
.subtitle { margin: 16px 0 0; max-width: 760px; font-size: clamp(18px, 2.2vw, 22px); line-height: 1.35; letter-spacing: -0.015em; font-weight: 450; color: var(--muted); text-wrap: balance; }
.subtitle span { font-weight: 600; }
.hook { max-width: 660px; margin: 24px 0 0; font-size: 16px; line-height: 1.6; color: var(--muted); }
.hook b { color: var(--ink); font-weight: 500; }
.buttons { display: flex; flex-wrap: wrap; gap: 8px; margin: 28px 0 44px; }
.btn { display: inline-flex; align-items: center; gap: 7px; padding: 7px 14px; border-radius: 10px;
  border: 1px solid var(--line-strong); background: var(--bg); color: var(--ink); font-size: 13.5px; font-weight: 500; text-decoration: none;
  transition: transform .12s ease-out, background .15s, border-color .15s; }
.btn:hover { background: var(--fill); }
.btn:active { transform: scale(0.97); }
.btn svg { width: 15px; height: 15px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.btn.primary { background: var(--ink); color: var(--bg); border-color: var(--ink); }
.btn.primary:hover { opacity: .85; background: var(--ink); }
.lede { margin-top: 40px; }
.lede p { font-size: 16px; line-height: 1.7; margin-bottom: 16px; }
.lede a { text-decoration-color: currentColor; }

/* ---------- sections: white / #fafafa alternation, hairline joins ---------- */
section { padding: 88px 0; }
section.band { background: var(--band); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
#video { padding: 56px 0; }
#controls { padding-top: 72px; }
.kicker { margin: 0 0 12px; font: 500 12px var(--mono); letter-spacing: .06em; text-transform: uppercase; color: var(--muted); }
h2 { margin: 0 0 12px; font-size: clamp(26px, 3.2vw, 32px); line-height: 1.15; letter-spacing: -0.025em; font-weight: 600; text-align: left; text-wrap: balance; }
h3 { margin: 0 0 8px; font-size: 18px; line-height: 1.3; letter-spacing: -0.015em; font-weight: 600; }
h4 { margin: 36px 0 8px; font-size: 16px; letter-spacing: -0.01em; font-weight: 600; }
.section-lead { text-wrap: pretty; max-width: 640px; margin: 0 0 36px; font-size: 16px; line-height: 1.65; color: var(--muted); }
.section-lead b { color: var(--ink); font-weight: 500; }
.note { margin-top: 22px; font-size: 13.5px; line-height: 1.6; color: var(--muted); }
.note a { color: var(--muted); text-decoration-color: currentColor; }

/* ---------- media ---------- */
.media { margin: 0; }
.media video, .media img { width: 100%; height: auto; border-radius: var(--radius); border: 1px solid var(--line); background: #fff; }
.media.plain img { padding: 14px; }
.media figcaption { margin: 10px 2px 0; font-size: 13px; line-height: 1.55; color: var(--muted); }
.media figcaption b { color: var(--ink); font-weight: 500; }
.hero-media video { aspect-ratio: 3.2 / 1; object-fit: cover; }
.tabs video { aspect-ratio: 2 / 1; object-fit: cover; object-position: top; }
.pair { align-items: start; }
.grid { display: grid; gap: 24px; }
.grid.two { grid-template-columns: repeat(2, 1fr); }
.grid.four { grid-template-columns: repeat(4, 1fr); gap: 14px; }
.grid.four video { aspect-ratio: 4 / 3; object-fit: cover; border-radius: var(--radius-sm); }
.grid.four figcaption { font-size: 13px; }
.grid.center { align-items: center; }

/* ---------- tabs: segmented control, semantic colour as a dot ---------- */
.tab-bar { display: inline-flex; gap: 2px; padding: 3px; margin: 0 0 18px; background: var(--fill); border: 1px solid var(--line); border-radius: 10px; }
.tab-bar button { display: inline-flex; align-items: center; gap: 8px; font: 500 13.5px var(--sans); padding: 6px 14px; border: 1px solid transparent; border-radius: 8px; cursor: pointer; background: transparent; color: var(--muted);
  transition: background .2s, color .2s, border-color .2s, transform .12s ease-out; }
.tab-bar button::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: var(--faint); transition: background .2s; }
.tab-bar button small { font-weight: 400; color: var(--faint); }
.tab-bar button:hover { color: var(--ink); }
.tab-bar button:active { transform: scale(0.97); }
.tab-bar button.active { background: var(--bg); color: var(--ink); border-color: var(--line-strong); box-shadow: 0 1px 2px rgba(0,0,0,.06); }
.tab-bar button.persona.active::before { background: var(--persona); }
.tab-bar button.body.active::before { background: var(--body); }
.tab-bar button.style.active::before { background: var(--style); }

/* ---------- capture / measure / retarget ---------- */
.steps { list-style: none; padding: 0; margin: 0 0 8px; display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.steps a { display: block; height: 100%; padding: 18px 20px 20px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--bg); text-decoration: none; transition: transform .15s ease-out, border-color .15s, background .15s; }
.steps a:hover { border-color: var(--line-strong); background: var(--band); }
.steps a:active { transform: scale(0.985); }
.steps .n { display: block; margin-bottom: 14px; font: 500 12px var(--mono); color: var(--muted); letter-spacing: .04em; }
.num { display: inline-flex; align-items: center; justify-content: center; width: 26px; height: 26px; margin-right: 12px; border-radius: 8px; background: var(--ink); color: var(--bg); font: 500 12.5px var(--mono); flex: none; }
.steps b { display: block; font-size: 17px; letter-spacing: -0.015em; }
.steps a > span:last-child { display: block; margin-top: 6px; font-size: 14px; line-height: 1.55; color: var(--muted); }
.step { margin-top: 72px; }
.step h3.stage { display: flex; align-items: center; margin: 0 0 14px; font-size: 22px; letter-spacing: -0.02em; }
#data p { max-width: 720px; }
#data p.callout { max-width: none; margin: 28px 0 20px; padding: 14px 18px; border-radius: var(--radius-sm); border: 1px solid var(--line); background: var(--band); font-size: 15px; }
.verdict { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 24px; }
.verdict > div { padding: 18px 20px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--bg); }
.verdict h5 { margin: 0 0 8px; font: 500 12px var(--mono); letter-spacing: .05em; text-transform: uppercase; }
.verdict h5::before { content: ""; display: inline-block; width: 8px; height: 8px; border-radius: 50%; margin-right: 8px; background: currentColor; }
.v-change h5 { color: var(--body); }
.v-keep h5 { color: var(--persona); }
.verdict p { margin: 0; font-size: 14px; line-height: 1.6; color: var(--muted); }

/* ---------- method ---------- */
h3.stage { margin: 40px 0 10px; }
.dot { display: inline-block; width: 9px; height: 9px; border-radius: 50%; margin-right: 10px; }
#method p { max-width: 720px; }
#method figure { margin: 24px 0; }

/* ---------- results / limits ---------- */
.proof { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin: 0 0 14px; }
.proof > div { padding: 20px 22px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--bg); }
.proof b small { font-size: .55em; font-weight: 500; color: var(--muted); letter-spacing: 0; }
.proof b { display: block; font-size: 30px; line-height: 1.1; letter-spacing: -0.035em; font-weight: 600; font-variant-numeric: tabular-nums; }
.proof span { display: block; margin-top: 8px; font-size: 13px; line-height: 1.5; color: var(--muted); }
.proofnote { margin: 0 0 40px; }
.limits { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; margin-top: 28px; }
.limits > div { padding: 20px 22px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--bg); }
.limits h5 { margin: 0 0 6px; font-size: 15px; font-weight: 600; letter-spacing: -0.01em; }
.limits p { margin: 0; font-size: 14px; line-height: 1.6; color: var(--muted); }

/* ---------- resources / bibtex ---------- */
.res { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-top: 28px; }
.res a { display: block; padding: 18px 20px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--bg); text-decoration: none; transition: transform .15s ease-out, border-color .15s; }
.res a:hover { border-color: var(--line-strong); }
.res a:active { transform: scale(0.985); }
.res b { display: block; font-size: 15px; font-weight: 600; letter-spacing: -0.01em; }
.res a b::after { content: " \2197"; color: var(--faint); font-weight: 400; }
.res span { display: block; margin-top: 2px; font-size: 13.5px; line-height: 1.45; color: var(--muted); }
.code { position: relative; border-radius: var(--radius); border: 1px solid var(--line); background: var(--fill); }
.code pre { margin: 0; padding: 20px 84px 20px 22px; overflow-x: auto; white-space: pre-wrap; word-break: break-word; font: 12.5px/1.7 var(--mono); }
.copy { position: absolute; top: 10px; right: 10px; padding: 4px 11px; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--bg); color: var(--ink); font: 500 12px var(--sans); cursor: pointer; transition: transform .12s ease-out; }
.copy:active { transform: scale(0.95); }
footer { padding: 36px 0 56px; border-top: 1px solid var(--line); font-size: 13px; color: var(--muted); }
footer p { margin: 0; }

/* ---------- abstract (collapsed) ---------- */
.abs { padding: 8px 0 24px; }
.abs details { border-radius: var(--radius); border: 1px solid var(--line); padding: 0 20px; background: var(--bg); }
.abs summary { cursor: pointer; padding: 14px 0; font-weight: 500; font-size: 14px; list-style: none; display: flex; justify-content: space-between; align-items: center; }
.abs summary::-webkit-details-marker { display: none; }
.abs summary::after { content: "+"; font: 400 18px var(--mono); color: var(--faint); }
.abs details[open] summary::after { content: "\2212"; }
.abs details p { font-size: 14.5px; color: var(--muted); }
.abs details p:last-child { margin-bottom: 20px; }

/* ---------- embedded data viewer ---------- */
.viewer { margin-top: 72px; }
.viewer h3 { font-size: 20px; letter-spacing: -0.02em; }
.plain { font-size: 15px; color: var(--muted); }
.viewer-frame { position: relative; height: 800px; margin-top: 16px; border-radius: var(--radius); border: 1px solid var(--line); overflow: hidden; background: var(--band); }
.viewer-frame iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; background: #fff; }
.viewer-load { position: absolute; inset: 0; width: 100%; border: 0; background: transparent; cursor: pointer; color: var(--ink); font: 500 15px var(--sans);
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 10px; }
.viewer-load svg { width: 52px; height: 52px; padding: 15px 13px 15px 17px; border-radius: 50%; background: var(--ink); fill: var(--bg); transition: transform .15s ease-out; }
.viewer-load:hover svg { transform: scale(1.06); }
.viewer-load:active svg { transform: scale(0.96); }
.viewer-load small { font-weight: 400; font-size: 12.5px; color: var(--muted); }

/* ---------- dark mode: white-baked figures become softly lit plates ---------- */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .media video, :root:not([data-theme="light"]) .media img { filter: brightness(.88) contrast(1.02); }
  :root:not([data-theme="light"]) .media.plain img { background: #d9d9dd; }
  :root:not([data-theme="light"]) .viewer-frame iframe { filter: brightness(.9); }
}

/* ---------- responsive ---------- */
@media (max-width: 860px) {
  section { padding: 60px 0; }
  .nav-links { display: flex; overflow-x: auto; white-space: nowrap; gap: 18px; max-width: 52vw; scrollbar-width: none; }
  .nav-links::-webkit-scrollbar { display: none; }
  .grid.two, .steps, .verdict, .proof, .res, .limits { grid-template-columns: 1fr; }
  .grid.four { grid-template-columns: repeat(2, 1fr); }
  .viewer-frame { height: 920px; }
  .step { margin-top: 56px; }
}
@media (max-width: 600px) { .hero-media video { aspect-ratio: 16 / 9; object-position: 50% 30%; } .hero { padding-top: 48px; } }

/* ---------- accessibility signals ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}
@media (prefers-reduced-transparency: reduce) {
  .nav { background: var(--bg); -webkit-backdrop-filter: none; backdrop-filter: none; }
}
@media (prefers-contrast: more) {
  :root { --line: #8a8a8a; --line-strong: #444; --muted: #3a3a3a; }
}
@media (max-width: 600px) { .nav-links { display: none; } }

.viewer-body .section-lead { margin-bottom: 8px; }
.viewer-frame { margin-top: 20px; }

/* ---------- left contents rail (wide screens, after the hero) ---------- */
.toc { position: fixed; left: max(24px, calc((100vw - 880px) / 2 - 200px)); top: 50%; z-index: 10; width: 150px; transform: translateY(-50%); opacity: 0; pointer-events: none; transition: opacity .25s; }
.toc.show { opacity: 1; pointer-events: auto; }
.toc ol { list-style: none; margin: 0; padding: 0; }
.toc ol ol { margin: 2px 0 4px; padding-left: 12px; }
.toc li { margin: 0; }
.toc a { display: block; position: relative; padding: 4px 0 4px 14px; font: 500 12px/1.3 var(--mono); letter-spacing: .02em; color: var(--faint); text-decoration: none; transition: color .15s; }
.toc a::before { content: ""; position: absolute; left: 0; top: 50%; width: 5px; height: 1px; background: var(--line-strong); transition: width .2s ease-out, background .2s; }
.toc a:hover { color: var(--ink); }
.toc a.active { color: var(--ink); }
.toc a.active::before { width: 9px; height: 2px; margin-top: -0.5px; background: var(--ink); }
.toc ol ol a { font-size: 11.5px; padding-left: 12px; }
@media (max-width: 1279px) { .toc { display: none; } }
@media (prefers-reduced-motion: reduce) { .toc, .toc a::before { transition: none; } }