:root {
  --uh-scarlet: #C8102E;
  --uh-scarlet-dark: #8C0A20;
  --uh-scarlet-soft: #FEEEF1;
  --uh-white: #FFFFFF;
  --uh-gray: #54585A;
  --uh-gray-light: #F4F4F5;
  --uh-gray-border: #E4E4E7;
  --uh-text: #1A1A1A;
  --uh-text-soft: #4A4A4E;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 24px rgba(200, 16, 46, 0.12);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: 'Source Sans 3', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  color: var(--uh-text);
  background: var(--uh-white);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* Navbar */
.navbar {
  position: sticky; top: 0; z-index: 100;
  background: var(--uh-scarlet);
  color: var(--uh-white);
  box-shadow: var(--shadow-md);
}
.nav-inner {
  max-width: 1200px; margin: 0 auto;
  padding: 0.9rem 1.5rem;
  display: flex; justify-content: space-between; align-items: center;
  gap: 1rem; flex-wrap: wrap;
}
.nav-brand {
  display: flex; align-items: center; gap: 0.7rem;
  font-weight: 700; font-size: 1.05rem;
  color: var(--uh-white); text-decoration: none;
}
.nav-brand .brand-mark {
  width: 36px; height: 36px;
  background: var(--uh-white); color: var(--uh-scarlet);
  border-radius: 6px; display: inline-flex; align-items: center; justify-content: center;
  font-family: 'Merriweather', serif; font-weight: 700;
}
.nav-links a {
  color: var(--uh-white); text-decoration: none; margin-left: 1.2rem;
  font-weight: 500; opacity: 0.88; transition: opacity 0.15s;
}
.nav-links a:hover { opacity: 1; text-decoration: underline; }

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--uh-scarlet) 0%, var(--uh-scarlet-dark) 100%);
  color: var(--uh-white);
  padding: 4.5rem 1.5rem 3.5rem;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: '';
  position: absolute; inset: 0;
  background-image:
    radial-gradient(circle at 20% 20%, rgba(255, 255, 255, 0.08), transparent 40%),
    radial-gradient(circle at 80% 80%, rgba(255, 255, 255, 0.06), transparent 35%);
  pointer-events: none;
}
.hero-inner {
  max-width: 1100px; margin: 0 auto;
  position: relative;
}
.hero-eyebrow {
  text-transform: uppercase; letter-spacing: 0.14em;
  font-size: 0.82rem; font-weight: 600;
  opacity: 0.85; margin-bottom: 0.6rem;
}
.hero h1 {
  font-family: 'Merriweather', serif;
  font-size: clamp(2rem, 5vw, 3.4rem);
  margin: 0 0 0.6rem;
  line-height: 1.1;
}
.hero-sub {
  font-size: 1.1rem; opacity: 0.95;
  max-width: 720px;
}
.hero-chips {
  display: flex; flex-wrap: wrap; gap: 0.5rem;
  margin-top: 1.6rem;
}
.chip {
  display: inline-flex; align-items: center; gap: 0.35rem;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  font-size: 0.88rem;
  color: var(--uh-white);
  backdrop-filter: blur(4px);
}

/* Main */
main { max-width: 1100px; margin: 0 auto; padding: 2.5rem 1.5rem 4rem; }

/* About */
.about {
  background: var(--uh-gray-light);
  border-left: 5px solid var(--uh-scarlet);
  padding: 1.5rem 1.75rem;
  border-radius: 0 8px 8px 0;
  margin-bottom: 3rem;
  font-size: 1.02rem;
}
.about p { margin: 0 0 0.6rem; }
.about p:last-child { margin: 0; }
.about a { color: var(--uh-scarlet); font-weight: 600; }
.about a:hover { color: var(--uh-scarlet-dark); }

/* Section headers */
h2 {
  font-family: 'Merriweather', serif;
  font-size: 1.8rem;
  margin: 0 0 0.3rem;
  color: var(--uh-text);
  display: flex; align-items: baseline; gap: 0.8rem;
  flex-wrap: wrap;
}
.semester-tag {
  font-family: 'Source Sans 3', sans-serif;
  font-size: 0.95rem;
  background: var(--uh-scarlet);
  color: var(--uh-white);
  padding: 0.25rem 0.7rem;
  border-radius: 4px;
  font-weight: 600;
}

.semester-block.current { margin-bottom: 3rem; }
.semester-block.upcoming { margin-bottom: 3rem; }
.semester-block.upcoming .semester-header { border-bottom-color: var(--uh-gray); }
.semester-tag.upcoming-tag { background: var(--uh-gray); }
.upcoming-note {
  color: var(--uh-text-soft);
  font-style: italic;
  font-size: 0.95rem;
  margin: -0.5rem 0 1.25rem;
}
.semester-header {
  border-bottom: 3px solid var(--uh-scarlet);
  padding-bottom: 0.6rem; margin-bottom: 1.5rem;
}

/* Talk cards */
.talks { display: flex; flex-direction: column; gap: 1rem; }
.talk-card {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: 0;
  background: var(--uh-white);
  border: 1px solid var(--uh-gray-border);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.15s, transform 0.15s;
}
.talk-card:hover {
  box-shadow: var(--shadow-lg);
}
.talk-card.holiday { grid-template-columns: 160px 1fr; opacity: 0.85; }
.talk-date {
  background: var(--uh-scarlet);
  color: var(--uh-white);
  padding: 1rem 1.1rem;
  display: flex; flex-direction: column; justify-content: center;
  text-align: center;
}
.date-main {
  font-weight: 700; font-size: 1rem;
  line-height: 1.25;
}
.date-time {
  display: block;
  font-size: 0.82rem;
  opacity: 0.92;
  margin-top: 0.25rem;
  font-weight: 500;
}
.talk-body { padding: 1rem 1.25rem 1.1rem; }
.talk-meta { margin-bottom: 0.4rem; }
.badge {
  display: inline-block;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-weight: 600;
  padding: 0.2rem 0.55rem;
  border-radius: 4px;
}
.badge-networks { background: #EEF2FF; color: #3730A3; }
.badge-virtual { background: #ECFDF5; color: #047857; }
.badge-location { background: var(--uh-gray-light); color: var(--uh-gray); }

.talk-title {
  font-family: 'Merriweather', serif;
  font-size: 1.15rem;
  margin: 0.2rem 0 0.45rem;
  color: var(--uh-text);
  line-height: 1.3;
}
.talk-speaker {
  color: var(--uh-text-soft);
  font-size: 0.98rem;
  margin-bottom: 0.7rem;
}
.speaker-name { font-weight: 600; color: var(--uh-text); }
.speaker-name.tbd { color: var(--uh-gray); font-weight: 500; }
.speaker-affil { color: var(--uh-text-soft); }
.speaker-affil::before { content: '· '; margin: 0 0.2em; color: var(--uh-gray); }
.event-details { margin: 0.4rem 0 0.8rem; font-size: 0.97rem; line-height: 1.5; }
.event-details p { margin: 0 0 0.35rem; }
.event-details a { color: var(--uh-scarlet-dark); }

.holiday-label {
  font-family: 'Merriweather', serif;
  font-size: 1.15rem;
  color: var(--uh-text);
  padding: 0.7rem 0;
}

/* Abstract */
.talk-abstract {
  margin-top: 0.3rem;
  border-top: 1px solid var(--uh-gray-border);
  padding-top: 0.75rem;
}
.talk-abstract summary {
  cursor: pointer;
  display: inline-flex; align-items: center; gap: 0.4rem;
  color: var(--uh-scarlet);
  font-weight: 600;
  font-size: 0.9rem;
  list-style: none;
  user-select: none;
  padding: 0.25rem 0;
  transition: color 0.15s;
}
.talk-abstract summary::-webkit-details-marker { display: none; }
.talk-abstract summary::before {
  content: '▸';
  transition: transform 0.15s;
  display: inline-block;
}
.talk-abstract[open] summary::before { transform: rotate(90deg); }
.talk-abstract summary:hover { color: var(--uh-scarlet-dark); }
.abstract-content {
  margin-top: 0.7rem;
  padding: 1rem 1.1rem;
  background: var(--uh-scarlet-soft);
  border-radius: 6px;
  border-left: 3px solid var(--uh-scarlet);
  color: var(--uh-text);
  font-size: 0.97rem;
  line-height: 1.65;
}
.abstract-content a { color: var(--uh-scarlet-dark); }

/* Past semester accordions */
.past-section-title {
  font-family: 'Merriweather', serif;
  font-size: 1.5rem;
  margin: 3rem 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--uh-gray-border);
}
details.semester-block.past {
  border: 1px solid var(--uh-gray-border);
  border-radius: 8px;
  margin-bottom: 0.75rem;
  background: var(--uh-white);
  overflow: hidden;
}
details.semester-block.past[open] {
  box-shadow: var(--shadow-md);
  border-color: var(--uh-scarlet);
}
.semester-summary {
  cursor: pointer;
  padding: 1rem 1.25rem;
  font-weight: 600;
  font-size: 1.05rem;
  display: flex; justify-content: space-between; align-items: center;
  list-style: none;
  user-select: none;
  transition: background 0.15s;
}
.semester-summary::-webkit-details-marker { display: none; }
.semester-summary::after {
  content: '+';
  color: var(--uh-scarlet);
  font-size: 1.4rem;
  font-weight: 700;
  line-height: 1;
  transition: transform 0.15s;
}
details[open] .semester-summary::after { content: '–'; }
.semester-summary:hover { background: var(--uh-scarlet-soft); }
.sem-name { color: var(--uh-text); }
.sem-count {
  color: var(--uh-gray);
  font-weight: 500;
}
details.semester-block.past .talks {
  padding: 0 1.25rem 1.25rem;
}

/* Footer */
footer {
  background: var(--uh-text);
  color: var(--uh-white);
  padding: 2rem 1.5rem;
  text-align: center;
  font-size: 0.9rem;
}
footer a { color: var(--uh-white); }
.footer-inner { max-width: 1100px; margin: 0 auto; opacity: 0.9; }

/* Mobile */
@media (max-width: 680px) {
  .talk-card { grid-template-columns: 1fr; }
  .talk-date {
    flex-direction: row; justify-content: flex-start;
    gap: 0.6rem; padding: 0.7rem 1.1rem; text-align: left;
  }
  .date-time { margin-top: 0; }
  .hero { padding: 3rem 1.25rem 2.5rem; }
  .nav-links a { margin-left: 0.8rem; font-size: 0.95rem; }
}