/* ============================================================================
   THEME — color, type, base layout
   The brand color comes from _config.yml so changing it once recolors
   the headline, section headings, links, and table header.
   ============================================================================ */

:root {
  --brand:        #E77500;
  --brand-hover:  #c96400;

  --bg:           #ffffff;
  --bg-soft:      #f8f8f9;     /* alternating table row */
  --bg-session:   #fff8df;     /* pale yellow session row */
  --text:         #1a1a1a;
  --text-muted:   #555;
  --text-soft:    #777;
  --border:       #e6e7eb;
  --border-soft:  #eef0f3;
}

html[data-theme="dark"] {
  --bg:           #0f1115;
  --bg-soft:      #161922;
  --bg-session:   #2a2410;
  --text:         #e8e8ea;
  --text-muted:   #b3b3b8;
  --text-soft:    #8a8a93;
  --border:       #2a2d38;
  --border-soft:  #1f222b;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background .2s ease, color .2s ease;
}

a {
  color: var(--brand);
  text-decoration: underline;
  text-underline-offset: 2px;
  text-decoration-thickness: 1px;
}
a:hover { color: var(--brand-hover); }

del { color: var(--text-soft); }

/* ============================================================================
   HEADER
   ============================================================================ */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: var(--bg);
  border-bottom: 1px solid var(--border-soft);
}
.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 1.1rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand { color: var(--brand); text-decoration: none; }
.brand:hover { color: var(--brand-hover); }
.brand .brand-text {
  font-weight: 800;
  font-size: 1.15rem;
  letter-spacing: -0.01em;
}
.brand img { height: 28px; width: auto; display: block; }

.nav-right { display: flex; align-items: center; gap: 1.25rem; }
.nav-right .nav-link {
  color: var(--text-muted);
  text-decoration: none;
  font-size: .95rem;
}
.nav-right .nav-link:hover { color: var(--text); }

/* Grouped nav: prefix + linked sub-items joined by a separator (e.g. "Princeton CS & ECE") */
.nav-right .nav-group {
  text-decoration: none;
  white-space: nowrap;
}
.nav-right .nav-group a {
  color: var(--text-muted);
  text-decoration: none;
}
.nav-right .nav-group a:hover { color: var(--text); }

.theme-toggle {
  appearance: none;
  background: transparent;
  border: 0;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
}
.theme-toggle:hover { color: var(--text); background: var(--bg-soft); }
.theme-toggle .icon-moon { display: none; }
html[data-theme="dark"] .theme-toggle .icon-sun  { display: none; }
html[data-theme="dark"] .theme-toggle .icon-moon { display: block; }

/* ============================================================================
   PAGE COLUMN — left-aligned narrow column
   ============================================================================ */
.page {
  max-width: 920px;
  margin: 0 auto;
  padding: 3rem 1.5rem 4rem;
}

.page p  { margin: 0 0 1rem 0; }
.page ul { padding-left: 1.4rem; }
.page li { margin-bottom: .35rem; }

/* ============================================================================
   HEADINGS — section titles in brand color, bold sans-serif
   ============================================================================ */
h2 {
  color: var(--brand);
  font-family: 'Inter', sans-serif;
  font-weight: 500;
  font-size: 1.3rem;
  letter-spacing: -0.02em;
  margin: 3rem 0 1rem 0;
  padding-bottom: .25rem;
  border-bottom: 1px solid var(--border-soft);
}

h3 {
  font-family: 'Inter', sans-serif;
  font-weight: 700;
  font-size: 1.05rem;
  margin: 1.6rem 0 .75rem 0;
}

/* ============================================================================
   HERO
   ============================================================================ */
.hero { margin: 2rem 0 1.5rem; }

.hero-big {
  color: var(--brand);
  font-family: 'Inter', sans-serif;
  font-weight: 800;
  font-size: clamp(3.5rem, 9vw, 6.5rem);
  line-height: 1;
  letter-spacing: -0.04em;
  margin: 0 0 1.25rem 0;
}

.hero-sub-top {
  color: var(--text-soft);
  font-family: 'Source Serif 4', Georgia, serif;
  font-weight: 300;
  font-size: clamp(1.6rem, 3.5vw, 2.4rem);
  line-height: 1.15;
  letter-spacing: -0.01em;
  margin: 0 0 .25rem 0;
}

.hero-sub-bottom {
  color: var(--brand);
  font-family: 'Inter', sans-serif;
  font-weight: 700;
  font-size: clamp(1.4rem, 3vw, 2rem);
  line-height: 1.2;
  letter-spacing: -0.01em;
  margin: 0 0 1rem 0;
}

.held-with { font-size: 1rem; margin: 1rem 0 0 0; }

/* ============================================================================
   KEY INFO — date / time / location quick-look
   ============================================================================ */
.key-info { margin: 1.5rem 0 2rem; }
.key-info p { margin: 0 0 .15rem 0; line-height: 1.7; }

/* ============================================================================
   TOPIC LIST (only used when intro.topics is non-empty)
   ============================================================================ */
.topic-list { margin: 1rem 0 2rem; }

/* ============================================================================
   SCHEDULE TABLE — brand-colored header bar, alternating rows,
   pale-yellow session rows
   ============================================================================ */
.schedule-wrap { overflow-x: auto; margin: 1rem 0 1.5rem; }

table.schedule,
table.students {
  width: 100%;
  border-collapse: collapse;
  font-size: .95rem;
}

table.schedule thead th,
table.students thead th {
  background: var(--brand);
  color: #fff;
  text-align: left;
  font-weight: 700;
  padding: .85rem 1rem;
  font-size: 1rem;
}

table.schedule td,
table.students td {
  padding: .9rem 1rem;
  border-bottom: 1px solid var(--border-soft);
  vertical-align: top;
}

/* alternate row striping for slot rows */
table.schedule tbody tr:nth-child(even):not(.session-row) td,
table.students tbody tr:nth-child(even) td {
  background: var(--bg-soft);
}

/* session header row in pale yellow, centered, bold */
table.schedule tr.session-row td {
  background: var(--bg-session);
  text-align: center;
  font-weight: 700;
  padding: .65rem 1rem;
}

table.schedule .time-cell {
  white-space: nowrap;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  width: 11rem;
}

/* tag pills [Keynote], [Paper], etc. */
.tag { display: inline; font-weight: 700; margin-right: .35rem; }
.tag-keynote { color: #b45309; }
.tag-paper   { color: #1d4ed8; }
.tag-talk    { color: #15803d; }
.tag-tool    { color: #7e22ce; }
html[data-theme="dark"] .tag-keynote { color: #fbbf24; }
html[data-theme="dark"] .tag-paper   { color: #93c5fd; }
html[data-theme="dark"] .tag-talk    { color: #86efac; }
html[data-theme="dark"] .tag-tool    { color: #e9d5ff; }

.remote { color: var(--text-soft); font-style: italic; }
.speaker-line, .authors-line {
  display: block;
  margin-top: .25rem;
  color: var(--text);
}
.authors-line { color: var(--text-muted); }
.pdf-link { display: block; margin-top: .25rem; font-size: .9rem; color: var(--text-soft); }
.pdf-link a { color: var(--text-soft); }
.pdf-link a:hover { color: var(--brand); }

/* ============================================================================
   STUDENT PRESENTATIONS — session sub-headings + presenter table
   ============================================================================ */
.student-session-title {
  font-size: 1.15rem;
  margin-top: 2rem;
  margin-bottom: .5rem;
  color: var(--text);
}
.student-chair {
  font-weight: 500;
  color: var(--text-muted);
  font-size: .95rem;
}

table.students td:first-child  { font-weight: 600; white-space: nowrap; }
table.students td:nth-child(2) { color: var(--text-muted); white-space: nowrap; }

/* ============================================================================
   KEYNOTE / SPEAKER CARDS
   ============================================================================ */
.speaker-card {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: 1.75rem;
  align-items: start;
  padding: 1.5rem 0 2rem;
  border-bottom: 1px solid var(--border-soft);
}
.speaker-card:last-of-type { border-bottom: 0; }

.speaker-photo img {
  width: 200px;
  height: 240px;
  object-fit: cover;
  display: block;
  background: var(--bg-soft);
  border: 1px solid var(--border);
}

.photo-placeholder {
  width: 200px; height: 240px;
  background: var(--bg-soft);
  border: 1px dashed var(--border);
  display: flex; align-items: center; justify-content: center;
  color: var(--text-soft); font-size: .85rem;
}
.photo-placeholder.square { width: 100%; aspect-ratio: 1 / 1; height: auto; }

.speaker-body p { margin-bottom: .85rem; }
.speaker-section { margin: 1rem 0; }
.speaker-section p { margin-bottom: .85rem; }

/* ============================================================================
   RSVP
   ============================================================================ */
.rsvp-link {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 1rem 0 .75rem 0;
}
.rsvp-link a {
  background: var(--brand);
  color: #fff;
  padding: .6rem 1.1rem;
  border-radius: 4px;
  text-decoration: none;
  display: inline-block;
}
.rsvp-link a:hover {
  background: var(--brand-hover);
  color: #fff;
}
.rsvp-closed {
  margin-left: .75rem;
  color: var(--text-soft);
  font-weight: 500;
  font-size: .95rem;
}
.rsvp-note {
  color: var(--text-muted);
  font-style: italic;
  font-size: .95rem;
}

/* ============================================================================
   ORGANIZERS GRID
   ============================================================================ */
.organizers-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0 1.5rem;
  margin: 1rem 0 1.5rem;
  border-top: 2px solid var(--brand);
  border-bottom: 2px solid var(--brand);
  padding: 1.25rem 0;
}

/* Single-organizer card layout: photo on the left, info on the right. */
.organizer-card {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: 1.75rem;
  align-items: start;
  margin: 1rem 0 1.5rem;
  border-top: 2px solid var(--brand);
  border-bottom: 2px solid var(--brand);
  padding: 1.5rem 0;
}
.organizer-card-photo img {
  width: 200px;
  height: 240px;
  object-fit: cover;
  display: block;
  background: var(--bg-soft);
  border: 1px solid var(--border);
}
.organizer-card-photo .photo-placeholder.square {
  width: 200px; height: 240px; aspect-ratio: auto;
}
.organizer-card-body p { margin: 0 0 .35rem; }
.organizer-card-name {
  font-weight: 600;
  font-size: 1.1rem;
}
.organizer-card-name a { color: var(--brand); text-decoration: underline; }
.organizer-card-role,
.organizer-card-affil {
  font-size: .95rem;
  color: var(--text-muted);
}

.organizer-photo {
  max-width: 220px;
}
.organizer-photo img {
  width: 100%;
  aspect-ratio: 1 / 1;
  object-fit: cover;
  display: block;
  background: var(--bg-soft);
  border: 1px solid var(--border);
}

.organizer-name {
  font-weight: 600;
  padding-top: .85rem;
  border-bottom: 1px solid var(--border-soft);
  padding-bottom: .35rem;
  margin-bottom: .35rem;
}
.organizer-name a { color: var(--brand); text-decoration: underline; }

.organizer-role,
.organizer-affil {
  font-size: .95rem;
  color: var(--text-muted);
  padding: .15rem 0;
}
.organizer-affil { padding-bottom: .25rem; }

.pc-list { margin: 1rem 0; }

/* ============================================================================
   LOCATION & DIRECTIONS
   ============================================================================ */
.directions-list {
  list-style: none;
  padding-left: 0;
  margin: .5rem 0 1.5rem;
}
.directions-list li {
  padding: .65rem 0;
  border-bottom: 1px dashed var(--border-soft);
}
.directions-list li:last-child { border-bottom: 0; }
.directions-list li strong { color: var(--text); }

/* ============================================================================
   FOOTER
   ============================================================================ */
.site-footer {
  border-top: 1px solid var(--border-soft);
  background: var(--bg-soft);
  padding: 2.5rem 1.5rem;
  margin-top: 4rem;
}
.footer-inner {
  max-width: 920px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  font-size: .95rem;
  color: var(--text-muted);
}
.footer-col h4 {
  color: var(--text);
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 .5rem 0;
}
.footer-logo {
  display: block;
  width: 100%;
  max-width: 220px;
  height: auto;
  margin: 0 0 .6rem 0;
}

/* ============================================================================
   RESPONSIVE
   ============================================================================ */
@media (max-width: 720px) {
  .hero-big { font-size: 3.5rem; }
  h2 { font-size: 1.5rem; }

  .speaker-card { grid-template-columns: 1fr; }
  .speaker-photo img,
  .photo-placeholder { width: 180px; height: 220px; }

  .organizers-grid { grid-template-columns: 1fr; gap: 1.5rem; padding: 1rem 0; }

  .organizer-card { grid-template-columns: 1fr; gap: 1rem; }
  .organizer-card-photo img,
  .organizer-card-photo .photo-placeholder.square { width: 180px; height: 220px; }

  .footer-inner { grid-template-columns: 1fr; gap: 1.25rem; }

  table.students td:first-child,
  table.students td:nth-child(2) { white-space: normal; }
}