:root {
  --bg: #ffffff;
  --bg-alt: #f5f7fa;
  --card: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --brand: #2563eb;
  --accent: #d97706;
  --border: rgba(0, 0, 0, 0.12);
}

* { box-sizing: border-box; }

/* Smooth scrolling for better navigation */
html {
  scroll-behavior: smooth;
}

html, body { height: 100%; }

body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  background: #ffffff;
}

/* Skip Links for Accessibility */
.skip-links {
  position: absolute;
  top: -100px;
  left: 0;
  z-index: 1000;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 8px;
  padding: 8px 16px;
  background: var(--brand);
  color: white;
  text-decoration: none;
  border-radius: 4px;
  font-weight: 600;
  transition: all 0.3s ease;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.skip-link:focus {
  top: 8px;
  outline: 2px solid #ffffff;
  outline-offset: 2px;
}

.skip-link + .skip-link {
  margin-left: 120px;
}

/* Focus styles for better accessibility */
*:focus {
  outline: 2px solid var(--brand);
  outline-offset: 2px;
}

button:focus,
a:focus {
  outline: 2px solid var(--brand);
  outline-offset: 2px;
}

/* Reduced motion for users who prefer it */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  
  html {
    scroll-behavior: auto;
  }
}

.container {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
  font-size: 18px;
}

.nav-toggle {
  display: none;
  background: #ffffff;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 10px;
}

.nav-list {
  display: flex;
  gap: 18px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-list a {
  color: var(--muted);
  text-decoration: none;
  font-weight: 600;
}

.nav-list a:hover { color: var(--text); }

.section {
  padding: 56px 0;
}

.section-alt {
  background: #f9fafb;
}

/* Alternate section backgrounds: odd -> white, even -> grey */
main > section:nth-of-type(odd) { background: #ffffff; }
main > section:nth-of-type(even) { background: #f5f7fa; }

.hero {
  padding-top: 80px;
  padding-bottom: 48px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr 280px;
  align-items: center;
  gap: 24px;
}

.hero-logo {
  display: flex;
  align-items: center;
  justify-content: center;
}

.hero-logo img {
  width: 100%;
  max-width: 380px;
  height: auto;
  filter: none;
}

h1 {
  margin: 0 0 8px 0;
  font-size: 40px;
}

.subtitle {
  margin: 0 0 16px 0;
  color: var(--muted);
  font-size: 18px;
}

.highlight {
  display: inline-block;
  background: rgba(31, 111, 235, 0.08);
  color: var(--brand);
  padding: 6px 10px;
  border: 1px solid rgba(31, 111, 235, 0.25);
  border-radius: 10px;
  font-weight: 700;
}

.meta { margin-top: 16px; }
.meta p { margin: 6px 0; }
.note { color: var(--muted); }

h2 { margin-top: 0; }

.bullets {
  padding-left: 18px;
}

.placeholder-card {
  margin-top: 16px;
  padding: 16px;
  border-radius: 12px;
  background: var(--card);
  border: 1px solid var(--border);
  color: var(--muted);
  box-shadow: 0 1px 2px rgba(0,0,0,0.04);
}

.program-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 16px;
}

.talk {
  display: grid;
  grid-template-columns: 120px 1fr;
  align-items: start;
  gap: 14px;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #ffffff;
}

.talk-break { background: #fbfbfb; }

.talk-time {
  font-weight: 700;
  color: var(--muted);
}

.talk-title {
  font-weight: 700;
  color: var(--text);
}

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

.committee-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 16px;
  margin-top: 16px;
}

.committee-member {
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #ffffff;
  box-shadow: 0 1px 2px rgba(0,0,0,0.04);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  opacity: 0;
}

.committee-member:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.12);
}

.member-name {
  font-weight: 700;
  color: var(--text);
  margin-bottom: 4px;
}

.member-name a {
  color: var(--brand);
  text-decoration: none;
}

.member-name a:hover {
  text-decoration: underline;
}

.member-affiliation {
  color: var(--muted);
  font-size: 14px;
}

.contact-note {
  margin-top: 20px;
  padding: 12px 16px;
  background: rgba(31, 111, 235, 0.08);
  border: 1px solid rgba(31, 111, 235, 0.25);
  border-radius: 10px;
  color: var(--text);
}

.contact-note a {
  color: var(--brand);
  text-decoration: none;
}

.contact-note a:hover {
  text-decoration: underline;
}

details a {
  color: var(--brand);
  text-decoration: none;
}

details a:hover {
  text-decoration: underline;
}

/* FAQ Details Styling */
details {
  margin-bottom: 16px;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--card);
  transition: all 0.2s ease;
}

details:hover {
  border-color: var(--brand);
  box-shadow: 0 2px 8px rgba(37, 99, 235, 0.1);
}

details summary {
  font-weight: 600;
  cursor: pointer;
  padding: 4px 0;
  color: var(--text);
  transition: color 0.2s ease;
  list-style: none;
  position: relative;
}

details summary::-webkit-details-marker {
  display: none;
}

details summary::before {
  content: "▶";
  display: inline-block;
  margin-right: 8px;
  transition: transform 0.2s ease;
  color: var(--brand);
}

details[open] summary::before {
  transform: rotate(90deg);
}

details summary:hover {
  color: var(--brand);
}

details p {
  margin: 12px 0 0 0;
  padding-top: 12px;
  border-top: 1px solid var(--border);
  line-height: 1.6;
}

details ul {
  margin: 12px 0 0 0;
  padding-top: 12px;
  border-top: 1px solid var(--border);
}

details ul li {
  margin-bottom: 8px;
}

/* Sponsors Section */
.sponsors-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
  margin: 24px 0;
}

.sponsor-item {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  transition: all 0.2s ease;
}

.sponsor-item:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.08);
  border-color: var(--brand);
}

.sponsor-logo {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.sponsor-logo img {
  max-width: 200px;
  max-height: 100px;
  width: auto;
  height: auto;
  object-fit: contain;
}

.sponsor-info h3 {
  margin: 0;
  font-size: 20px;
  font-weight: 600;
  color: var(--text);
}

.sponsor-info p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.sponsor-note {
  margin-top: 32px;
  padding: 16px;
  background: var(--bg-alt);
  border-radius: 8px;
  text-align: center;
}

.sponsor-note p {
  margin: 0;
  font-style: italic;
  color: var(--muted);
}

.sponsor-note a {
  color: var(--brand);
  text-decoration: none;
}

.sponsor-note a:hover {
  text-decoration: underline;
}

/* Font Awesome icon styling */
.fab.fa-x-twitter {
  margin-right: 2px;
  color: inherit;
}

.fab.fa-twitter {
  margin-right: 2px;
  color: inherit;
}

/* Ensure icons display inline with text */
i.fab {
  display: inline;
  font-style: normal;
}

/* BIU Sponsor specific styling */
.sponsor-item:nth-child(2) {
  background: #0A4128;
}

.sponsor-item:nth-child(2):hover {
  background: #0A4128;
  border-color: #ffffff;
}

@media (max-width: 720px) {
  .talk { grid-template-columns: 1fr; }
}

.site-footer {
  border-top: 1px solid var(--border);
  background: #f5f7fa;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 20px 0;
}

.footer-links { display: flex; gap: 16px; }

.footer-links a { color: var(--muted); text-decoration: none; }
.footer-links a:hover { color: var(--text); }

/* Back to Top Button */
.back-to-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 50px;
  height: 50px;
  background: var(--brand);
  color: white;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
  transition: all 0.3s ease;
  z-index: 100;
}

.back-to-top:hover {
  background: #1d4ed8;
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.4);
}

.back-to-top.visible {
  display: flex;
  animation: fadeInUp 0.3s ease;
}

/* Loading animations */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* Page load animation */
.section {
  animation: fadeIn 0.6s ease-in-out;
}

@media (max-width: 720px) {
  .nav-toggle { 
    display: inline-block;
    padding: 12px;
    font-size: 18px;
    background: none;
    border: 1px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
    min-width: 44px;
    min-height: 44px;
  }
  
  .nav-toggle:hover {
    background: var(--bg-alt);
    border-color: var(--brand);
  }
  
  .nav-list { 
    display: none; 
    position: absolute; 
    right: 20px; 
    top: 64px; 
    flex-direction: column; 
    background: #ffffff; 
    border: 1px solid var(--border); 
    border-radius: 10px; 
    padding: 16px; 
    box-shadow: 0 8px 24px rgba(0,0,0,0.12);
    min-width: 200px;
    animation: fadeInUp 0.2s ease;
  }
  
  .nav-list.open { 
    display: flex; 
  }
  
  .nav-list li {
    margin: 0;
  }
  
  .nav-list a {
    display: block;
    padding: 12px 16px;
    margin: 4px 0;
    border-radius: 6px;
    transition: all 0.2s ease;
    min-height: 44px;
    display: flex;
    align-items: center;
  }
  
  .nav-list a:hover {
    background: var(--bg-alt);
    color: var(--brand);
  }
  
  .hero-grid { 
    grid-template-columns: 1fr; 
  }
  
  .back-to-top {
    bottom: 16px;
    right: 16px;
    width: 48px;
    height: 48px;
  }
  
  /* Better touch targets on mobile */
  .committee-member a {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
  }
  
  .contact-note a {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    padding: 4px 0;
  }
  
  /* Mobile sponsors styling */
  .sponsors-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }
  
  .sponsor-item {
    padding: 16px;
  }
  
  .sponsor-logo img {
    max-width: 200px;
    max-height: 100px;
  }
}