/* ==========================================================================
   Root Variables & Reset
   ========================================================================== */
:root {
  --bg-dark: #05070d;
  --card-bg: rgba(255, 255, 255, 0.04);
  --card-border: rgba(255, 255, 255, 0.08);
  --accent-cyan: #38bdf8;
  --accent-blue: #3b82f6;
  --text-main: #e5e7eb;
  --text-muted: #9ca3af;
  --radius: 14px;
  --max-width: 1100px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg-dark);
  color: var(--text-main);
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-family: 'Outfit', 'Inter', sans-serif;
  font-weight: 700;
  margin: 0;
}

p {
  margin: 0;
  color: var(--text-muted);
}

a {
  color: inherit;
}

ul {
  list-style: none;
  margin: 0;
}

img {
  max-width: 100%;
  display: block;
}

/* ==========================================================================
   Background Canvas
   ========================================================================== */
#bg-canvas {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: -2;
  background: radial-gradient(ellipse at top, #0b1120 0%, #05070d 60%);
}

.bg-overlay {
  position: fixed;
  inset: 0;
  z-index: -1;
  background: linear-gradient(180deg, rgba(5, 7, 13, 0) 0%, rgba(5, 7, 13, 0.4) 60%, var(--bg-dark) 100%);
  pointer-events: none;
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(5, 7, 13, 0.75);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--card-border);
}

nav {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1.5rem;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.logo {
  font-family: 'Outfit', sans-serif;
  font-weight: 800;
  font-size: 1.25rem;
  color: #fff;
  text-decoration: none;
  letter-spacing: 0.02em;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  padding: 0;
}

.nav-links a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.92rem;
  font-weight: 500;
  transition: color 0.2s ease;
}

.nav-links a:hover {
  color: var(--accent-cyan);
}

/* ==========================================================================
   Hero
   ========================================================================== */
.hero {
  position: relative;
  z-index: 0;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 5.5rem 1.5rem 4rem;
  text-align: center;
  overflow: hidden;
}

.badge {
  display: inline-block;
  padding: 0.4rem 1rem;
  border-radius: 999px;
  background: rgba(56, 189, 248, 0.1);
  border: 1px solid rgba(56, 189, 248, 0.3);
  color: var(--accent-cyan);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 1.5rem;
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.5rem);
  color: #fff;
  background: linear-gradient(120deg, #fff 30%, var(--accent-cyan) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 1rem;
}

.hero > p {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 700px;
  margin: 0 auto;
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.6rem;
  margin-top: 1.5rem;
}

.pill {
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-muted);
  font-size: 0.8rem;
}

.btn-group {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin-top: 2.25rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.8rem 1.5rem;
  border-radius: 10px;
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.btn-primary {
  background: linear-gradient(120deg, var(--accent-blue), var(--accent-cyan));
  color: #05070d;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(56, 189, 248, 0.35);
}

.btn-secondary {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-main);
}

.btn-secondary:hover {
  transform: translateY(-2px);
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
}

/* ==========================================================================
   Layout Container & Sections
   ========================================================================== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem 5rem;
}

section {
  padding: 3.5rem 0;
  scroll-margin-top: 80px;
}

.section-title {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 1.7rem;
  color: #fff;
  margin-bottom: 1.75rem;
}

.section-title i {
  color: var(--accent-cyan);
  font-size: 1.4rem;
}

.section-sub {
  color: var(--text-muted);
  margin-top: -1.25rem;
  margin-bottom: 1.75rem;
  max-width: 720px;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 2rem;
  backdrop-filter: blur(10px);
}

/* ==========================================================================
   Topics Grid
   ========================================================================== */
.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.5rem;
}

.topic-item {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  backdrop-filter: blur(10px);
  transition: transform 0.3s ease, border-color 0.3s ease;
}

.topic-item:hover {
  transform: translateY(-4px);
  border-color: var(--accent-cyan);
}

.topic-item h3 {
  font-size: 1.05rem;
  color: #fff;
  display: flex;
  align-items: center;
  gap: 0.55rem;
  margin-bottom: 0.6rem;
}

.topic-item h3 i {
  color: var(--accent-cyan);
}

.topic-item p {
  font-size: 0.92rem;
}

/* ==========================================================================
   Schedule / Timeline
   ========================================================================== */
.schedule-list {
  display: flex;
  flex-direction: column;
  gap: 0;
  padding: 0;
}

.schedule-row {
  display: grid;
  grid-template-columns: 150px 1fr;
  gap: 1rem;
  padding: 1rem 0;
  border-bottom: 1px solid var(--card-border);
  align-items: baseline;
}

.schedule-row:last-child {
  border-bottom: none;
}

.schedule-time {
  color: var(--accent-cyan);
  font-weight: 600;
  font-size: 0.9rem;
  white-space: nowrap;
}

.schedule-desc {
  color: var(--text-main);
  font-weight: 500;
}

.note {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: 1.25rem;
  font-style: italic;
}

/* ==========================================================================
   Dates List
   ========================================================================== */
.dates-list {
  padding: 0;
}

.date-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 1rem 0;
  border-bottom: 1px solid var(--card-border);
}

.date-row:last-child {
  border-bottom: none;
}

.date-label {
  color: var(--text-main);
  font-weight: 600;
}

.date-val {
  color: var(--accent-cyan);
  font-weight: 600;
}

/* ==========================================================================
   Footer
   ========================================================================== */
footer {
  text-align: center;
  padding: 3rem 1.5rem;
  border-top: 1px solid var(--card-border);
  color: var(--text-muted);
  font-size: 0.9rem;
}

.contact-line {
  margin-top: 0.75rem;
}

.contact-line a {
  color: var(--accent-cyan);
  text-decoration: none;
}

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

/* ==========================================================================
   Profile Cards (Speakers, Organizers & PC)
   ========================================================================== */
.profile-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
}

.pc-grid {
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
}

.profile-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  text-align: center;
  backdrop-filter: blur(10px);
  transition: transform 0.3s ease, border-color 0.3s ease;
}

.profile-card:hover {
  transform: translateY(-4px);
  border-color: var(--accent-cyan);
}

.profile-card.compact {
  padding: 1rem;
}

.profile-img {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  object-fit: cover;
  margin: 0 auto 1rem;
  border: 2px solid var(--accent-cyan);
}

.profile-img-sm {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  object-fit: cover;
  margin: 0 auto 0.75rem;
  border: 2px solid var(--accent-blue);
}

.profile-haoyan {
  object-position: 50% 32%;
}

.profile-card h3 {
  font-size: 1.2rem;
  color: #fff;
  margin-bottom: 0.25rem;
}

.profile-card h4 {
  font-size: 1rem;
  color: #fff;
}

.profile-name-link {
  color: inherit;
  text-decoration: none;
  transition: color 0.2s ease;
}

.profile-name-link:hover,
.profile-name-link:focus-visible {
  color: var(--accent-cyan);
}

.affiliation {
  color: var(--accent-cyan);
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 0.5rem;
}

.bio {
  color: var(--text-muted);
  font-size: 0.85rem;
  line-height: 1.4;
}

/* Guidelines List & Links */
.sub-title {
  font-size: 1.2rem;
  color: var(--accent-cyan);
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.guidelines-list {
  padding-left: 1.25rem;
  color: var(--text-muted);
}

.guidelines-list li {
  margin-bottom: 0.75rem;
  line-height: 1.5;
}

.guidelines-list strong {
  color: #fff;
}

.link-highlight {
  color: var(--accent-cyan);
  text-decoration: none;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-top: 0.25rem;
}

.link-highlight:hover {
  text-decoration: underline;
}

/* ==========================================================================
   Responsive
   ========================================================================== */
@media (max-width: 640px) {
  nav {
    flex-direction: column;
    align-items: flex-start;
  }

  .nav-links {
    gap: 0.5rem 1rem;
    font-size: 0.85rem;
  }

  .schedule-row {
    grid-template-columns: 1fr;
    gap: 0.25rem;
  }

  .date-row {
    flex-direction: column;
    gap: 0.25rem;
  }
}