/* ---------- tokens ---------- */
:root {
  --navy: #14274e;
  --navy-2: #143163;
  --ink: #2b2f3a;
  --muted: #5d6474;
  --accent: #a31f34;        /* MIT red, used sparingly */
  --accent-warm: #d9822b;   /* "perturbed" orange from the paper figures */
  --ok: #1f8a4c;
  --bad: #b3261e;
  --paper: #ffffff;
  --paper-2: #f5f6f9;
  --line: #e6e8ee;
  --radius: 12px;
  --shadow: 0 6px 24px rgba(20, 39, 78, .10);
  --font-title: 'Poppins', system-ui, sans-serif;
  --font-body: 'Quicksand', system-ui, sans-serif;
  --font-mono: 'Roboto Mono', ui-monospace, monospace;
}

html { scroll-behavior: smooth; }
body {
  font-family: var(--font-body);
  color: var(--ink);
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
}
.section { padding: 3.5rem 1.25rem; }
.section.is-feature { background: linear-gradient(180deg, #fafbfd 0%, var(--paper-2) 100%); }
@media (max-width: 768px) { .section { padding: 2.5rem 1rem; } }

/* ---------- hero: sticky stage that collapses into a slider ---------- */
.hero-stage {
  position: relative;
  /* 100svh of sticky stage + the scroll distance over which the hero collapses */
  height: calc(100svh + var(--collapse, 70vh));
  background: #0b1020;
  color: #fff;
}
.hero-sticky {
  position: sticky; top: 0;
  height: 100svh;
  overflow: hidden;
  display: flex; flex-direction: column;
}
.slider { position: relative; flex: 1; min-height: 0; touch-action: pan-y; }
.slide {
  position: absolute; left: 50%; top: 50%;
  width: var(--w, 100vw); height: var(--h, 100svh);
  transform: translate(-50%, -50%) translateX(var(--x, 0px)) scale(var(--s, 1));
  opacity: var(--o, 1);
  border-radius: var(--r, 0px);
  overflow: hidden; background: #000;
  box-shadow: 0 18px 50px rgba(0,0,0,.45);
  will-change: transform, width, height;
  cursor: pointer;
}
.slide.is-active { cursor: default; z-index: 2; }
.slide video { width: 100%; height: 100%; object-fit: cover; object-position: 50% 0; display: block; background: #000; }
.speed-badge {
  position: absolute; left: 1.25rem; top: 1.1rem; z-index: 4;
  padding: .45rem 1.1rem;
  border-radius: 999px;
  background: rgba(5,8,20,.55);
  border: 1px solid rgba(255,255,255,.25);
  color: rgba(255,255,255,.92);
  font-size: 1.5rem; font-weight: 700; letter-spacing: .02em; line-height: 1.2;
  backdrop-filter: blur(4px);
  pointer-events: none;
}
@media (max-width: 768px) { .speed-badge { left: .7rem; top: .7rem; padding: .3rem .8rem; font-size: 1.05rem; } }

.slide-shade {
  position: absolute; inset: 0; pointer-events: none;
  background: linear-gradient(180deg, rgba(5,8,20,.25) 0%, rgba(5,8,20,0) 35%, rgba(5,8,20,.45) 62%, rgba(5,8,20,.85) 100%);
  opacity: var(--shade, 1);
}

.hero-copy {
  position: absolute; left: 0; right: 0; bottom: 0; z-index: 3;
  padding: 0 1.25rem clamp(3rem, 8vh, 5.5rem);
  text-shadow: 0 2px 18px rgba(0,0,0,.55);
  opacity: var(--copy, 1);
  pointer-events: none;
}
.hero-copy a { pointer-events: auto; }
.hero-title {
  font-family: var(--font-title); font-weight: 700;
  font-size: clamp(1.75rem, 4.6vw, 3.6rem); line-height: 1.12;
  margin: 0 auto .8rem; max-width: 30ch; text-wrap: balance; color: #fff;
}
.hero-venue {
  font-family: var(--font-title); font-weight: 500;
  font-size: clamp(.85rem, 1.2vw, 1rem); letter-spacing: .06em;
  color: rgba(255,255,255,.85); margin: 0;
}
.hero-scroll {
  display: inline-flex; align-items: center; justify-content: center;
  width: 40px; height: 40px; margin-top: 1rem;
  border: 1.5px solid rgba(255,255,255,.6); border-radius: 50%;
  color: #fff; animation: bob 2.2s ease-in-out infinite;
}
.hero-scroll:hover { background: rgba(255,255,255,.12); color: #fff; }
@keyframes bob { 0%,100% { transform: translateY(0); } 50% { transform: translateY(6px); } }

.slider-nav {
  position: absolute; top: 50%; z-index: 4;
  width: 46px; height: 46px; border-radius: 50%; border: 1px solid rgba(255,255,255,.35);
  background: rgba(10,14,30,.55); color: #fff; font-size: 1rem; cursor: pointer;
  display: grid; place-items: center; backdrop-filter: blur(6px);
  transform: translateY(-50%);
  opacity: var(--ui-nav, 0); pointer-events: none;      /* desktop: fade in as the hero collapses */
  transition: background .15s, transform .15s;
}
.slider.is-nav-ready .slider-nav { pointer-events: auto; }
.slider-nav:hover { background: rgba(20,49,99,.85); transform: translateY(-50%) scale(1.06); }
.slider-nav.prev { left: max(.75rem, calc(50% - var(--w1, 960px) / 2 - 62px)); }
.slider-nav.next { right: max(.75rem, calc(50% - var(--w1, 960px) / 2 - 62px)); }


.slide-meta {
  position: absolute; left: 50%; transform: translateX(-50%);
  top: calc(50% + var(--h, 100svh) / 2 + 14px);
  width: min(var(--w1, 960px), 100vw - 2rem);
  opacity: var(--ui, 0); z-index: 3; text-align: center;
  pointer-events: none;
}
.slider.is-nav-ready .slide-meta { pointer-events: auto; }
.slider-dots { display: flex; justify-content: center; gap: .5rem; margin-bottom: .55rem; }
.slider-dots button {
  border: 0; padding: 0; cursor: pointer;
  height: 8px; width: 8px; border-radius: 999px; background: rgba(255,255,255,.35);
  transition: width .2s, background .2s;
}
.slider-dots button.is-active { width: 26px; background: #fff; }
.slide-caption { font-size: .92rem; line-height: 1.5; color: rgba(255,255,255,.85); margin: 0; }
.slide-caption strong { color: #fff; font-family: var(--font-title); font-weight: 600; }

/* phones: no scroll-collapse; title above the card slider, which is usable immediately */
@media (max-width: 768px) {
  .hero-stage { height: auto; }
  .hero-sticky { position: static; height: auto; overflow: hidden; flex-direction: column; }
  .hero-copy { position: static; order: 1; padding: 3rem 1rem 1.25rem; text-shadow: none; }
  .hero-venue { color: rgba(255,255,255,.8); }
  .hero-title { max-width: none; }
  .hero-scroll { display: none; }
  .slider { order: 2; flex: none; height: calc(69vw + 150px); }
  .slide { top: calc(var(--h, 69vw) / 2 + 4px); }
  .slide-meta { top: calc(var(--h, 69vw) + 4px + 14px); }
  .slide-shade { display: none; }
  .slider-nav { width: 38px; height: 38px; font-size: .85rem; top: calc(var(--h, 69vw) / 2 + 4px); }
  .slider-nav.prev { left: .5rem; } .slider-nav.next { right: .5rem; }
  .slider-nav { opacity: 1 !important; pointer-events: auto; }
  .slide-caption { font-size: .85rem; }
}

/* ---------- paper head ---------- */
.paper-head { padding-top: 3.5rem; }
.publication-title {
  font-family: var(--font-title); font-weight: 600;
  font-size: clamp(1.6rem, 3.2vw, 2.5rem); line-height: 1.2;
  color: var(--navy); margin-bottom: .4rem !important;
}
.publication-venue {
  font-family: var(--font-title); font-weight: 500; color: var(--accent);
  letter-spacing: .04em; margin-bottom: 1.4rem;
}
.publication-authors { font-size: clamp(1rem, 1.6vw, 1.25rem); font-weight: 500; line-height: 1.7; }
.author-block { display: inline-block; margin: 0 .35rem; white-space: nowrap; }
.publication-authors a { color: #50549b; }
.publication-authors a:hover { color: var(--navy); text-decoration: underline; }
.publication-authors sup { font-size: .6em; margin-left: 1px; color: var(--muted); }
.publication-institutes { margin-top: .6rem; font-size: clamp(.95rem, 1.3vw, 1.1rem); color: var(--ink); }
.inst-block { display: inline-block; margin: 0 .7rem; }
.publication-notes { margin-top: .35rem; font-size: .85rem; color: var(--muted); }
.publication-notes span { display: inline-block; margin: 0 .6rem; }

.affiliation-logos {
  display: flex; justify-content: center; align-items: center; gap: 2rem;
  margin: 1.4rem auto .4rem; flex-wrap: wrap;
}
.logo-slot { display: inline-flex; align-items: center; }
.affiliation-logos img { height: 54px; width: auto; object-fit: contain; }
.affiliation-logos .logo-yonsei-emblem { height: 50px; margin-right: .55rem; }
.affiliation-logos .logo-mit { height: 40px; margin-right: .7rem; }
.affiliation-logos .logo-biomimetics { height: 56px; }
.affiliation-logos .logo-rophi { height: 42px; }
@media (max-width: 768px) {
  .affiliation-logos { gap: 1.5rem; }
  .affiliation-logos img { height: 40px; }
  .affiliation-logos .logo-yonsei-emblem { height: 36px; margin-right: .4rem; }
  .affiliation-logos .logo-mit { height: 29px; margin-right: .5rem; }
  .affiliation-logos .logo-biomimetics { height: 40px; }
  .affiliation-logos .logo-rophi { height: 30px; }
}

.link-blocks { margin-top: 1.4rem; display: flex; flex-wrap: wrap; justify-content: center; gap: .5rem; }
.link-button {
  font-family: var(--font-body); font-weight: 600;
  color: #f5f5f5 !important; background: var(--navy-2); border-color: var(--navy-2);
  padding-left: 1.2rem; padding-right: 1.3rem;
  transition: transform .15s, box-shadow .15s;
}
.link-button:hover { background: var(--navy); border-color: var(--navy); transform: translateY(-1px); box-shadow: 0 6px 16px rgba(20,39,78,.25); }
.link-button.is-disabled { opacity: .45; cursor: not-allowed; pointer-events: none; }

.tldr {
  margin: 2.2rem auto 0;
  font-size: clamp(1rem, 1.4vw, 1.12rem); line-height: 1.65;
  padding: 1.1rem 1.4rem;
  border-left: 4px solid var(--navy-2); background: var(--paper-2); border-radius: 0 var(--radius) var(--radius) 0;
  text-align: left;
}
.tldr strong { font-family: var(--font-title); color: var(--navy); }

/* ---------- highlights ---------- */
.highlight-card {
  height: 100%; background: #fff; border: 1px solid var(--line); border-radius: 14px;
  padding: 1.5rem 1.35rem; transition: transform .15s, box-shadow .15s;
}
.highlight-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); }
.hl-icon {
  width: 42px; height: 42px; border-radius: 10px; display: grid; place-items: center;
  background: var(--navy); color: #fff; font-size: 1.1rem; margin-bottom: .9rem;
}
.highlight-card h3 { font-family: var(--font-title); font-weight: 600; font-size: 1.05rem; color: var(--navy); margin-bottom: .5rem; line-height: 1.3; }
.highlight-card p { color: var(--ink); font-size: .95rem; line-height: 1.6; }

/* ---------- sections ---------- */
.section-title {
  font-family: var(--font-title); font-weight: 600;
  font-size: clamp(1.4rem, 2.4vw, 1.9rem); color: var(--navy);
  margin-bottom: .8rem; line-height: 1.25;
}
.section-title::after { content: ""; display: block; width: 56px; height: 3px; background: var(--accent); margin-top: .6rem; border-radius: 2px; }
.section-lead { color: var(--ink); font-size: 1.02rem; line-height: 1.7; margin-bottom: 1.8rem; }
.abstract-text p { font-size: 1.02rem; line-height: 1.75; }

/* figures */
.fig { margin: 0 auto 1.5rem; }
/* one content width everywhere: text, figures, videos and the hero card all share the 960px column */
.container.is-max-desktop { max-width: 960px; }
.fig video { width: 100%; display: block; border-radius: 10px; box-shadow: var(--shadow); background: #000; }
/* paper figures are trimmed tight, so mount them on a white mat with a soft border */
.fig img {
  width: 100%; display: block; box-sizing: border-box;
  padding: 1.1rem 1.25rem; background: #fff;
  border: 1px solid var(--line); border-radius: 12px;
  box-shadow: 0 4px 18px rgba(20, 39, 78, .07);
}
.fig.chart img { padding: 1.1rem 1.25rem .9rem; }
@media (max-width: 768px) { .fig img { padding: .75rem .8rem; border-radius: 10px; } }
.fig-caption { margin-top: .8rem; color: var(--muted); font-size: .93rem; line-height: 1.55; }
.tag-label { color: var(--accent); font-weight: 700; }

/* method steps */
.method-steps { margin-top: 1.2rem; }
.method-steps h3 { font-family: var(--font-title); font-weight: 600; font-size: 1.05rem; color: var(--navy); margin: .5rem 0 .4rem; }
.method-steps p { font-size: .95rem; line-height: 1.65; }
.step-num {
  width: 32px; height: 32px; border-radius: 50%; background: var(--navy); color: #fff;
  font-family: var(--font-title); font-weight: 600; display: grid; place-items: center; font-size: .95rem;
}

/* simulation */
.sim-grid { margin-bottom: 1.5rem; }
.sim-card { position: relative; }
.sim-card video { aspect-ratio: 480 / 390; object-fit: cover; background: #0e1a2b; }
.sim-card.fail video { box-shadow: 0 0 0 3px rgba(179,38,30,.35), var(--shadow); }
.sim-card.pass video { box-shadow: 0 0 0 3px rgba(31,138,76,.45), var(--shadow); }
.sim-badge {
  position: absolute; top: 10px; left: 10px; z-index: 2;
  background: rgba(0,0,0,.65); color: #fff; font-family: var(--font-title); font-weight: 600;
  font-size: .8rem; padding: 3px 10px; border-radius: 999px; letter-spacing: .02em;
}
.verdict { font-weight: 700; color: var(--bad); margin-right: .3rem; }
.verdict.ok { color: var(--ok); }
.chart-row { margin-top: .5rem; }
.chart-wide { margin-top: 1.5rem; }


.fun-legend {
  display: flex; align-items: center; justify-content: center; gap: .65rem;
  margin-top: .7rem; font-size: .78rem; color: var(--muted);
}
.fun-legend .legend-scale { display: inline-flex; flex-direction: column; gap: 2px; }
.fun-legend .legend-bar {
  display: block; width: 160px; height: 9px; border-radius: 3px;
  border: 1px solid var(--line);
  /* inferno, matching the paper's "distance to object surface" colormap */
  background: linear-gradient(90deg, #fcffa4 0%, #fca50a 25%, #dd513a 50%, #932667 70%, #420a68 85%, #000004 100%);
}
.fun-legend .legend-ticks { display: flex; justify-content: space-between; width: 160px; font-variant-numeric: tabular-nums; }

.sub-title {
  font-family: var(--font-title); font-weight: 600; font-size: 1.15rem; color: var(--navy);
  text-align: center; margin: 2.2rem 0 1rem;
}
.chart-row .fig-caption { text-align: center; }
/* equal-height chart cards so side-by-side captions start on the same line */
@media (min-width: 769px) { .chart-row .fig.chart img { height: 330px; object-fit: contain; } }

/* real world tabs */
.rw-picker { display: flex; flex-wrap: wrap; justify-content: center; gap: .6rem; margin-bottom: 1rem; }
.rw-chip {
  display: flex; align-items: center; gap: .6rem;
  padding: .3rem .85rem .3rem .3rem; background: #fff;
  border: 1px solid #dfe2ea; border-radius: 999px; cursor: pointer;
  font-family: var(--font-title); font-size: .9rem; font-weight: 600; color: #4a4f5c;
  transition: border-color .15s, color .15s, box-shadow .15s, transform .15s;
}
.rw-chip img { width: 46px; height: 34px; object-fit: cover; border-radius: 999px; }
.rw-chip:hover { transform: translateY(-1px); border-color: #c9cdd8; box-shadow: 0 4px 14px rgba(0,0,0,.08); }
.rw-chip.is-active { color: var(--navy); border-color: var(--navy); box-shadow: 0 4px 16px rgba(20,39,78,.18); }

.rw-panel { display: none; }
.rw-panel.is-active { display: block; animation: fade .25s ease; }
@keyframes fade { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }
.rw-panel video {
  width: 100%; display: block; border-radius: 10px; background: #0b1020;
  box-shadow: 0 8px 30px rgba(0,0,0,.18);
}
.rw-caption { margin-top: .8rem; color: var(--muted); font-size: .95rem; line-height: 1.55; text-align: center; }
.rw-table {
  width: auto; max-width: 100%; margin: 2rem auto 0;
  font-size: .95rem; background: transparent;
}
.rw-table caption {
  caption-side: top; text-align: center; color: var(--muted);
  font-size: .9rem; padding-bottom: .7rem;
}
.rw-table th, .rw-table td {
  padding: .55em 1.5em; white-space: nowrap; text-align: right;
  border-color: var(--line) !important;
}
.rw-table th:first-child, .rw-table td:first-child { text-align: left; padding-left: .25em; }
.rw-table th:last-child, .rw-table td:last-child { padding-right: .25em; }
.rw-table th { font-family: var(--font-title); font-weight: 600; color: var(--navy); }
.rw-table tbody tr:last-child td { border-bottom-width: 0; }
.rw-note { color: var(--muted); font-size: .9rem; margin-top: .9rem; text-align: center; }
@media (max-width: 768px) {
  .rw-chip span { font-size: .8rem; }
  .rw-chip img { width: 38px; height: 28px; }
  .rw-table { font-size: .8rem; width: 100%; }
  .rw-table th, .rw-table td { padding: .45em .35em; }
  .rw-table th { white-space: normal; }   /* let long headers wrap instead of overflowing */
}

/* bibtex */
.citation-box { position: relative; background: var(--paper-2); border: 1px solid var(--line); border-radius: var(--radius); padding: 1.25rem 1.4rem; }
.citation-box pre {
  margin: 0; background: transparent; padding: 0; color: var(--ink);
  font-family: var(--font-mono); font-size: .86rem; line-height: 1.6;
  white-space: pre-wrap; word-break: break-word;
}
.copy-btn {
  position: absolute; top: .8rem; right: .8rem;
  background: var(--navy-2); color: #fff; border: 0; border-radius: 6px;
  padding: .4rem .75rem; font-family: var(--font-body); font-weight: 600; font-size: .82rem; cursor: pointer;
}
.copy-btn:hover { background: var(--navy); }

/* footer */
.footer { background: #fafbfd; padding: 2.5rem 1.25rem; font-size: .9rem; color: var(--muted); }
.footer-links { display: flex; justify-content: center; gap: 1.2rem; margin-bottom: 1rem; }
.icon-link { font-size: 1.5rem; color: var(--navy); }
.icon-link:hover { color: var(--accent); }
.footer a { color: var(--navy); }

@media (prefers-reduced-motion: reduce) {
  .hero-scroll { animation: none; }
  html { scroll-behavior: auto; }
}