/* ===========================================================
   Seungwoo Choi — personal site
   =========================================================== */

:root {
  --navy:      #16324f;
  --navy-soft: #24507a;
  --accent:    #2b8cc4;
  --accent-dk: #1d6d9c;
  --ink:       #1f2933;
  --ink-2:     #3e4c59;
  --muted:     #6b7a89;
  --line:      #e3e8ee;
  --bg:        #ffffff;
  --bg-alt:    #f6f8fa;
  --tag-bg:    #eaf2f8;
  --maxw:      880px;
  --radius:    8px;

  /* publication keyword colours, shared by the titles and the legend.
     All four clear 4.5:1 on white — brighter greens/cyans do not. */
  --k-sim:     #047857;
  --k-comp:    #6d28d9;
  --k-vqa:     #b45309;
  --k-err:     #dc2626;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 76px; }

body {
  margin: 0;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent-dk); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

.muted { color: var(--muted); }

code {
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  font-size: 0.88em;
  background: var(--bg-alt);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 0.05em 0.35em;
}

/* ---------- top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  height: 60px;
}

.brand {
  font-weight: 700;
  font-size: 1.02rem;
  color: var(--navy);
  letter-spacing: -0.01em;
  white-space: nowrap;
}
.brand:hover { text-decoration: none; color: var(--accent-dk); }

.topnav {
  display: flex;
  gap: 18px;
  overflow-x: auto;
  scrollbar-width: none;
}
.topnav::-webkit-scrollbar { display: none; }

.topnav a {
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--ink-2);
  white-space: nowrap;
  padding: 4px 0;
  border-bottom: 2px solid transparent;
}
.topnav a:hover { color: var(--accent-dk); text-decoration: none; }
.topnav a.active { color: var(--accent-dk); border-bottom-color: var(--accent); }

/* ---------- hero ---------- */

.hero {
  display: flex;
  align-items: center;
  gap: 40px;
  padding: 56px 0 44px;
  border-bottom: 1px solid var(--line);
}

.hero-text { flex: 1 1 auto; min-width: 0; }

.hero h1 {
  margin: 0 0 6px;
  font-family: "Lora", Georgia, serif;
  font-size: 2.3rem;
  font-weight: 600;
  line-height: 1.15;
  color: var(--navy);
  letter-spacing: -0.015em;
}

.tagline {
  margin: 0 0 14px;
  /* sized so the first line clears the hero column without wrapping */
  font-size: 0.97rem;
  color: var(--ink-2);
}

.contact {
  list-style: none;
  margin: 0 0 16px;
  padding: 0;
  font-size: 0.93rem;
  color: var(--ink-2);
}
.contact li { display: flex; align-items: center; gap: 8px; }
.contact .ico { color: var(--accent); width: 1em; text-align: center; }

.links { display: flex; flex-wrap: wrap; gap: 8px; }

.links a {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 6px 14px;
  font-size: 0.86rem;
  font-weight: 500;
  color: var(--navy);
  background: var(--bg-alt);
  border: 1px solid var(--line);
  border-radius: 999px;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.links a:hover {
  text-decoration: none;
  background: var(--tag-bg);
  border-color: var(--accent);
  color: var(--accent-dk);
}

/* icons inherit the pill's text colour, so they follow the hover state too */
.links svg {
  width: 14px;
  height: 14px;
  flex: 0 0 auto;
  fill: currentColor;
}

.hero-photo { flex: 0 0 auto; }

.hero-photo img,
.hero-photo .photo-fallback {
  /* block, not inline — an inline img leaves baseline space below it, which
     would make .hero-photo taller than wide and the gate overlay an ellipse */
  display: block;
  width: 168px;
  height: 168px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--bg-alt);
  box-shadow: 0 4px 18px rgba(22, 50, 79, 0.12);
}

.hero-photo .photo-fallback {
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(140deg, var(--navy), var(--accent));
  color: #fff;
  font-family: "Lora", Georgia, serif;
  font-size: 3rem;
  font-weight: 600;
  letter-spacing: 0.04em;
}

/* ---------- eight gates (click the portrait) ----------
   Everything here is created by main.js, so with JS off the hero photo
   stays an ordinary, non-interactive image. */

.hero-photo.gates { position: relative; cursor: pointer; }

/* hover ring: hints that the portrait does something when clicked */
.hero-photo.gates img,
.hero-photo.gates .photo-fallback { transition: border-color 0.2s, box-shadow 0.2s; }
.hero-photo.gates:hover img,
.hero-photo.gates:hover .photo-fallback {
  border-color: #22c55e;
  box-shadow: 0 0 0 3px rgba(34, 197, 94, 0.25), 0 4px 18px rgba(22, 50, 79, 0.12);
}
/* once a gate is open the flame owns the border, so drop the hover ring */
.hero-photo.gates.seventh:hover img,
.hero-photo.gates.final:hover img { box-shadow: none; }

.hero-photo.gates:focus-visible { outline: 2px solid var(--accent); outline-offset: 8px; border-radius: 50%; }

/* the chakra diagram, flashed over the portrait before the swap.
   `inset: 0` covers the photo's border ring too, so no frame shows through. */
.gate-flash {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  overflow: hidden;
  background: #000;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.22s, visibility 0.22s;
  pointer-events: none;
}
.hero-photo.flashing .gate-flash { opacity: 1; visibility: visible; }

/* the portrait rattles only while a gate is being forced open, harder each time */
.hero-photo.flashing { animation: gate-shake 0.08s linear infinite; }

@keyframes gate-shake {
  0%, 100% { transform: translate(0, 0); }
  25%      { transform: translate(calc(var(--shake, 2px) * -1), var(--shake, 2px)); }
  50%      { transform: translate(var(--shake, 2px), calc(var(--shake, 2px) * -1)); }
  75%      { transform: translate(var(--shake, 2px), var(--shake, 2px)); }
}

/* 8gates.jpg is pre-cropped so the figure is dead centre, so plain centring is
   enough — no nudge, and it holds at any photo size. Width is a percentage of
   the circle, so the zoom scales with the breakpoint too. flex-shrink:0 is
   load-bearing: a flex item would otherwise be squeezed back to container width. */
.gate-flash-inner {
  position: relative;
  flex: 0 0 auto;
  width: 153%;
  line-height: 0;
}
/* Two classes, not one: this has to outrank `.hero-photo img`, and in particular
   its mobile override further down the file, which otherwise wins on source
   order and pins the diagram to the portrait's 128px box and cover-crop.
   The same reason the rest of the portrait's styling is reset here. */
.hero-photo .gate-flash img {
  display: block;
  width: 100%;
  height: auto;
  border: 0;
  border-radius: 0;
  object-fit: fill;
  box-shadow: none;
  animation: none;
}

.gate-pin {
  position: absolute;
  width: 17px;
  height: 17px;
  margin: -8.5px 0 0 -8.5px;
  border: 2px solid #22c55e;
  border-radius: 50%;
  box-shadow: 0 0 9px #22c55e;
  animation: gate-pin-pulse 0.85s ease-in-out infinite;
}
.hero-photo.seventh .gate-pin { border-color: #22d3ee; box-shadow: 0 0 11px #22d3ee; }
.hero-photo.final   .gate-pin { border-color: #ef4444; box-shadow: 0 0 11px #ef4444; }

@keyframes gate-pin-pulse {
  0%, 100% { transform: scale(1);    opacity: 1; }
  50%      { transform: scale(1.35); opacity: 0.5; }
}

/* the eighth gate shockwave */
.gate-wave {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 176px;
  height: 176px;
  margin: -88px 0 0 -88px;
  border: 3px solid var(--wave, #ef4444);
  border-radius: 50%;
  opacity: 0;
  pointer-events: none;
}
.hero-photo.burst .gate-wave { animation: gate-wave 0.95s ease-out; }

@keyframes gate-wave {
  from { transform: scale(0.9); opacity: 0.9; border-width: 9px; }
  to   { transform: scale(3.4); opacity: 0;   border-width: 1px; }
}

.gate-label {
  position: absolute;
  top: calc(100% + 16px);
  left: 50%;
  transform: translateX(-50%);
  white-space: nowrap;
  text-align: center;
  font-size: 0.8rem;
  font-weight: 600;
  line-height: 1.35;
  color: #15803d;
  opacity: 0;
  transition: opacity 0.2s;
  pointer-events: none;
}
.hero-photo.flashing .gate-label { opacity: 1; }
.hero-photo.seventh .gate-label { color: #0e7490; }
.hero-photo.final   .gate-label { color: #dc2626; }
.gate-label b {
  display: block;
  font-family: "Lora", Georgia, serif;
  font-size: 1.15rem;
  letter-spacing: 0.08em;
}

/* seventh gate: blue fire. eighth: red. both stay lit until reset. */
.hero-photo.seventh { --wave: #22d3ee; }
.hero-photo.final   { --wave: #ef4444; }

.hero-photo.seventh img,
.hero-photo.seventh .photo-fallback {
  animation: gate-flame-blue 0.55s ease-in-out infinite alternate;
}

@keyframes gate-flame-blue {
  from {
    border-color: #3b82f6;
    box-shadow: 0 0 26px 4px #3b82f6, 0 0 62px 10px rgba(59, 130, 246, 0.45);
  }
  to {
    border-color: #67e8f9;
    box-shadow: 0 0 46px 11px #22d3ee, 0 0 96px 20px rgba(34, 211, 238, 0.5);
  }
}

.hero-photo.final img,
.hero-photo.final .photo-fallback {
  animation: gate-flame 0.55s ease-in-out infinite alternate;
}

@keyframes gate-flame {
  from {
    border-color: #ef4444;
    box-shadow: 0 0 26px 4px #ef4444, 0 0 62px 10px rgba(239, 68, 68, 0.45);
  }
  to {
    border-color: #fb923c;
    box-shadow: 0 0 46px 11px #f97316, 0 0 96px 20px rgba(249, 115, 22, 0.5);
  }
}

/* respect a reduced-motion preference: keep the gate names, drop the motion */
@media (prefers-reduced-motion: reduce) {
  .gate-pin { animation: none; }
  .hero-photo.flashing { animation: none; }
  .hero-photo.seventh img,
  .hero-photo.seventh .photo-fallback {
    animation: none;
    border-color: #3b82f6;
    box-shadow: 0 0 26px 4px #3b82f6;
  }
  .hero-photo.final img,
  .hero-photo.final .photo-fallback {
    animation: none;
    border-color: #ef4444;
    box-shadow: 0 0 26px 4px #ef4444;
  }
  .hero-photo.burst .gate-wave { animation: none; }
}

/* ---------- sections ---------- */

section { padding: 40px 0 8px; }

section h2 {
  margin: 0 0 20px;
  padding-bottom: 8px;
  font-family: "Lora", Georgia, serif;
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--navy);
  border-bottom: 2px solid var(--line);
}

.sub {
  margin: 24px 0 10px;
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent-dk);
}
.sub:first-child { margin-top: 0; }

.section-note { margin: -8px 0 18px; font-size: 0.88rem; color: var(--muted); }

section p { margin: 0 0 14px; }

.bullets { margin: 16px 0 0; padding-left: 20px; }
.bullets li { margin-bottom: 6px; }

/* ---------- timeline ---------- */

.timeline { list-style: none; margin: 0; padding: 0; }

.timeline li {
  display: grid;
  grid-template-columns: 64px 180px 1fr;
  gap: 0 20px;
  padding: 0 0 22px 0;
}

.tl-logo { align-self: start; padding-top: 1px; }

/* real school marks differ in aspect ratio, so letterbox rather than squash */
.tl-logo img {
  display: block;
  width: 64px;
  height: 64px;
  object-fit: contain;
}

/* funders are wide wordmarks (Hyundai is 7:1), so they get a landscape slot
   instead of the square one the university seals use */
.logos-wide li { grid-template-columns: 110px 180px 1fr; }
.logos-wide .tl-logo { padding-top: 4px; }
.logos-wide .tl-logo img { width: 110px; height: 44px; }

.tl-when {
  font-size: 0.86rem;
  font-weight: 600;
  color: var(--accent-dk);
  padding-top: 3px;
}

.tl-what { min-width: 0; }

.tl-what h3 {
  margin: 0 0 2px;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--navy);
}

.tl-what .role {
  font-size: 0.86rem;
  font-weight: 500;
  color: var(--muted);
  margin-left: 6px;
}

.tl-what .meta { margin: 0; font-size: 0.9rem; color: var(--ink-2); }

/* ---------- publications ---------- */

.pubs { list-style: none; margin: 0; padding: 0; counter-reset: pub; }

.pubs li {
  display: flex;
  gap: 18px;
  padding: 14px 0;
  border-bottom: 1px solid var(--line);
}
.pubs li:last-child { border-bottom: none; }

/* venue badge with the author position stacked under it */
.venue-col {
  flex: 0 0 100px;
  align-self: flex-start;
  display: flex;
  flex-direction: column;
  gap: 5px;
  margin-top: 3px;
}
.venue-col .tag { text-align: center; }

.venue {
  text-align: center;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: #fff;
  background: var(--navy-soft);
  border-radius: 4px;
  padding: 3px 6px;
}

.pub-body { flex: 1 1 auto; min-width: 0; }

.pub-body h3 {
  margin: 0 0 3px;
  font-size: 1rem;
  font-weight: 500;
  line-height: 1.45;
  color: var(--ink);
}
.pub-body h3 a { color: inherit; }
/* underline on hover instead of recolouring, so the keyword coding survives */
.pub-body h3 a:hover { color: var(--accent-dk); text-decoration: underline; }

/* Keywords sit flush with the rest of the title until their topic is ticked;
   main.js then adds hl-* to the section and only those groups light up. */
.pub-body h3 b { font-weight: inherit; color: inherit; transition: color 0.15s; }

#publications.hl-sim  .pub-body h3 b.k-sim,
#publications.hl-comp .pub-body h3 b.k-comp,
#publications.hl-vqa  .pub-body h3 b.k-vqa,
#publications.hl-err  .pub-body h3 b.k-err { font-weight: 700; }

#publications.hl-sim  .pub-body h3 b.k-sim  { color: var(--k-sim); }
#publications.hl-comp .pub-body h3 b.k-comp { color: var(--k-comp); }
#publications.hl-vqa  .pub-body h3 b.k-vqa  { color: var(--k-vqa); }
#publications.hl-err  .pub-body h3 b.k-err  { color: var(--k-err); }

/* legend, parked on the right of the section heading */
#publications h2 {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 2px 20px;
}

.pub-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 3px 14px;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.01em;
}
.pub-legend label {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  cursor: pointer;
  opacity: 0.7;
  transition: opacity 0.15s;
  user-select: none;
}
.pub-legend label:hover,
.pub-legend label:has(:checked) { opacity: 1; }

/* the checkbox is the swatch: empty box when off, filled when on */
.pub-legend input {
  appearance: none;
  -webkit-appearance: none;
  margin: 0;
  width: 12px;
  height: 12px;
  border: 2px solid currentColor;
  border-radius: 3px;
  cursor: pointer;
  transition: background 0.15s;
}
.pub-legend input:checked { background: currentColor; }
.pub-legend input:focus-visible { outline: 2px solid currentColor; outline-offset: 2px; }

.pub-legend .k-sim  { color: var(--k-sim); }
.pub-legend .k-comp { color: var(--k-comp); }
.pub-legend .k-vqa  { color: var(--k-vqa); }
.pub-legend .k-err  { color: var(--k-err); }

/* only takes up space while a filter is active */
.pub-count { margin: -8px 0 16px; font-size: 0.86rem; font-weight: 600; color: var(--ink-2); }
.pub-count:empty { display: none; }

/* filtered-out papers */
.pubs li[hidden] { display: none; }

.pub-body p { margin: 0 0 6px; font-size: 0.9rem; color: var(--ink-2); }

/* must outrank `.pub-body p` above, hence the two-class selector */
.pub-body .pub-where {
  margin: 0 0 5px;
  font-size: 0.82rem;
  font-style: italic;
  color: var(--muted);
}

/* ---------- tags ---------- */

.tag {
  display: inline-block;
  font-size: 0.74rem;
  font-weight: 600;
  color: var(--accent-dk);
  background: var(--tag-bg);
  border-radius: 4px;
  padding: 2px 8px;
  white-space: nowrap;
}
.tag.first { color: #fff; background: var(--accent); }

/* ---------- projects ---------- */

.projects { display: flex; flex-direction: column; gap: 18px; }

.project {
  padding: 18px 20px;
  background: var(--bg-alt);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
}

.project .when {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent-dk);
  margin-bottom: 2px;
}

.project h3 {
  margin: 0 0 8px;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--navy);
  line-height: 1.4;
}

.project ul { margin: 0; padding-left: 20px; }
.project li { margin-bottom: 5px; font-size: 0.93rem; color: var(--ink-2); }
.project li:last-child { margin-bottom: 0; }

/* ---------- plain lists ---------- */

.plain { list-style: none; margin: 0; padding: 0; }

.plain li {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 10px;
  padding: 7px 0;
  border-bottom: 1px solid var(--line);
  font-size: 0.95rem;
}
.plain li:last-child { border-bottom: none; }
.plain li b { font-weight: 600; color: var(--ink); }
.plain li b a { color: inherit; }
.plain li b a:hover { color: var(--accent-dk); text-decoration: underline; }
.plain li .muted { font-size: 0.86rem; }

.plain li .tag { flex: 0 0 auto; min-width: 110px; text-align: center; }
.talks li .tag { min-width: 140px; }

/* ---------- collapsible block ---------- */

.fold summary {
  display: flex;
  align-items: baseline;
  gap: 10px;
  cursor: pointer;
  list-style: none;
  margin: 24px 0 10px;
}
.fold summary::-webkit-details-marker { display: none; }

/* the .sub inside a summary already carries its own top margin */
.fold summary .sub { margin: 0; }

.fold summary::before {
  content: "";
  flex: 0 0 auto;
  width: 0;
  height: 0;
  border-left: 5px solid var(--accent);
  border-top: 4px solid transparent;
  border-bottom: 4px solid transparent;
  transition: transform 0.2s;
}
.fold[open] summary::before { transform: rotate(90deg); }

.fold summary:hover .sub { color: var(--accent); }
.fold summary:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 4px; }

.fold-count { font-size: 0.78rem; font-weight: 500; color: var(--muted); }

/* ---------- skills ---------- */

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 8px 40px;
}

.skill-list { list-style: none; margin: 0; padding: 0; }

.skill-list li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 5px 0;
  font-size: 0.93rem;
  font-weight: 500;
}

.dots { display: inline-flex; gap: 5px; flex: 0 0 auto; }

.dots i {
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--line);
  display: block;
}
.dots i.on { background: var(--accent); }

/* ---------- footer ---------- */

footer {
  margin-top: 56px;
  padding: 22px 0;
  border-top: 1px solid var(--line);
  background: var(--bg-alt);
}
footer p { margin: 0; font-size: 0.85rem; color: var(--muted); text-align: center; }

/* ---------- responsive ---------- */

@media (max-width: 720px) {
  .hero {
    flex-direction: column-reverse;
    align-items: flex-start;
    gap: 22px;
    padding-top: 36px;
  }
  .hero h1 { font-size: 1.9rem; }
  .hero-photo img, .hero-photo .photo-fallback { width: 128px; height: 128px; }

  /* the hero stacks photo-first here, so the gate name goes beside it, not under */
  .gate-wave { width: 136px; height: 136px; margin: -68px 0 0 -68px; }
  .gate-label {
    top: 50%;
    left: calc(100% + 14px);
    transform: translateY(-50%);
    text-align: left;
  }

  /* logo keeps its own column; date stacks above the details */
  .timeline li { grid-template-columns: 64px 1fr; gap: 2px 16px; }
  .logos-wide li { grid-template-columns: 88px 1fr; }
  .logos-wide .tl-logo img { width: 88px; height: 36px; }
  .tl-logo { grid-column: 1; grid-row: 1 / span 2; }
  .tl-when { grid-column: 2; grid-row: 1; }
  .tl-what { grid-column: 2; grid-row: 2; }

  .pubs li { flex-direction: column; gap: 8px; }
  /* badge and author position sit side by side once the column is gone */
  .venue-col { flex: none; flex-direction: row; align-items: center; gap: 8px; margin-top: 0; }
  .venue { min-width: 100px; }

  .plain li .tag, .talks li .tag { min-width: 0; }
}

@media (max-width: 560px) {
  .topbar-inner { height: auto; flex-direction: column; align-items: flex-start; gap: 6px; padding-top: 10px; padding-bottom: 8px; }
  html { scroll-padding-top: 110px; }
  .topnav { width: 100%; }
}

/* ---------- print ---------- */

@media print {
  .topbar, footer, .links { display: none; }
  body { font-size: 11pt; }
  section { page-break-inside: avoid; }
}