/* ---------- Reset & base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  color: #1c2230;
  background: #ffffff;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

:root {
  --navy:        #0b2545;
  --navy-deep:   #061a36;
  --navy-soft:   #13315c;
  --accent:      #c8553d;   /* warm IJCAI-style accent */
  --accent-soft: #e07a5f;
  --gold:        #d4a437;
  --ink:         #1c2230;
  --muted:       #5b6478;
  --line:        #e3e6ec;
  --bg-alt:      #f5f7fb;
  --bg-soft:     #fafbfd;
  --radius:      10px;
  --maxw:        1100px;
}

img { max-width: 100%; display: block; }
a { color: var(--navy-soft); text-decoration: none; transition: color .15s ease; }
a:hover { color: var(--accent); }

h1, h2, h3, h4 {
  font-family: 'Source Serif 4', Georgia, 'Times New Roman', serif;
  color: var(--navy-deep);
  line-height: 1.2;
  margin: 0 0 .6em;
  font-weight: 700;
  letter-spacing: -0.01em;
}

p { margin: 0 0 1em; }

.container {
  width: 100%;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255,255,255,0.92);
  backdrop-filter: saturate(180%) blur(10px);
  -webkit-backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  height: 72px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--navy-deep);
}
.brand:hover { color: var(--navy-deep); }
.brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px; height: 40px;
  background: var(--navy);
  color: #fff;
  border-radius: 8px;
  font-weight: 700;
  font-size: 13px;
  letter-spacing: 0.04em;
}
.brand-text { display: flex; flex-direction: column; line-height: 1.15; }
.brand-title { font-weight: 600; font-size: 14px; color: var(--navy-deep); }
.brand-sub { font-size: 12px; color: var(--muted); }

.site-nav { display: flex; }
.nav-list {
  display: flex;
  gap: 8px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-list a {
  display: inline-block;
  padding: 8px 14px;
  font-size: 14px;
  font-weight: 500;
  color: #2c3346;
  border-radius: 6px;
}
.nav-list a:hover { background: var(--bg-alt); color: var(--navy-deep); }

.nav-toggle {
  display: none;
  background: none;
  border: 0;
  cursor: pointer;
  padding: 8px;
  flex-direction: column;
  gap: 4px;
}
.nav-toggle span {
  display: block;
  width: 22px; height: 2px;
  background: var(--navy-deep);
  border-radius: 2px;
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  background:
    radial-gradient(1200px 500px at 80% -200px, rgba(212,164,55,0.12), transparent 60%),
    radial-gradient(900px 400px at -10% 110%, rgba(200,85,61,0.10), transparent 60%),
    linear-gradient(180deg, var(--navy-deep) 0%, var(--navy) 100%);
  color: #f1f4fb;
  padding: 24px 0 88px;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.04) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse at center, #000 30%, transparent 75%);
  -webkit-mask-image: radial-gradient(ellipse at center, #000 30%, transparent 75%);
  pointer-events: none;
}
.hero-inner { position: relative; }
.eyebrow {
  display: inline-block;
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--gold);
  border: 1px solid rgba(212,164,55,0.4);
  padding: 6px 12px;
  border-radius: 999px;
  margin-bottom: 24px;
}
.hero h1 {
  color: #fff;
  font-size: clamp(2rem, 4.4vw, 3.25rem);
  max-width: 22ch;
  margin-bottom: 20px;
}
.lede {
  font-size: clamp(1.05rem, 1.4vw, 1.2rem);
  max-width: 60ch;
  color: #d6def0;
  margin-bottom: 32px;
}
.hero-meta {
  list-style: none;
  margin: 0 0 36px;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  max-width: 720px;
}
.hero-meta li {
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: var(--radius);
  padding: 14px 16px;
  font-size: 14px;
  color: #d6def0;
}
.hero-meta strong {
  display: block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gold);
  margin-bottom: 4px;
}
.hero-cta { display: flex; flex-wrap: wrap; gap: 12px; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-block;
  padding: 12px 22px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 14px;
  letter-spacing: 0.01em;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform .12s ease, background .15s ease, color .15s ease, border-color .15s ease;
}
.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover { background: var(--accent-soft); color: #fff; transform: translateY(-1px); }
.btn-ghost {
  background: transparent;
  color: #fff;
  border-color: rgba(255,255,255,0.35);
}
.btn-ghost:hover { background: rgba(255,255,255,0.08); color: #fff; border-color: #fff; }

/* ---------- Sections ---------- */
.section {
  padding: 88px 0;
}
.section-alt {
  background: var(--bg-alt);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.section-title {
  font-size: clamp(1.6rem, 2.4vw, 2.1rem);
  margin-bottom: 12px;
  position: relative;
  padding-bottom: 14px;
}
.section-title::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 56px; height: 3px;
  background: var(--accent);
  border-radius: 2px;
}
.section-intro {
  color: var(--muted);
  font-size: 1.05rem;
  max-width: 60ch;
  margin-bottom: 36px;
}
.prose p, .prose ul { color: #2c3346; }
.prose ul { padding-left: 1.2em; margin: 0 0 1em; }
.prose li { margin-bottom: 6px; }
.prose h3 {
  font-size: 1.15rem;
  margin-top: 8px;
  margin-bottom: 10px;
}

/* ---------- Cards (overview) ---------- */
.cards {
  margin-top: 40px;
  display: grid;
  grid-template-columns: repeat(3, minmax(0,1fr));
  gap: 20px;
}
.card {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  position: relative;
  transition: transform .15s ease, box-shadow .15s ease, border-color .15s ease;
}
.card::before {
  content: "";
  position: absolute;
  left: 24px; top: 0;
  width: 36px; height: 3px;
  background: var(--accent);
  border-radius: 0 0 2px 2px;
}
.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 28px -18px rgba(11,37,69,0.35);
  border-color: #d6dbe4;
}
.card h3 {
  font-size: 1.1rem;
  margin-top: 12px;
  margin-bottom: 8px;
}
.card p { color: var(--muted); margin: 0; font-size: 0.95rem; }

/* ---------- Outline ---------- */
.outline {
  display: grid;
  gap: 28px;
  grid-template-columns: repeat(2, minmax(0,1fr));
}
.outline-part {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 28px 8px;
}
.outline-part-head {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 18px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--line);
}
.part-tag {
  display: inline-block;
  background: var(--navy);
  color: #fff;
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding: 4px 10px;
  border-radius: 999px;
  font-weight: 600;
}
.outline-part-head h3 {
  font-size: 1.2rem;
  margin: 0;
}
.lecture {
  display: grid;
  grid-template-columns: 44px 1fr;
  gap: 18px;
  padding: 18px 0;
  border-bottom: 1px dashed var(--line);
}
.lecture:last-of-type { border-bottom: 0; }
.lecture-num {
  width: 44px; height: 44px;
  border-radius: 8px;
  background: linear-gradient(135deg, var(--navy) 0%, var(--navy-soft) 100%);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
  letter-spacing: 0.04em;
}
.lecture-body h4 {
  font-family: 'Inter', sans-serif;
  font-size: 1rem;
  font-weight: 600;
  margin: 4px 0 8px;
  color: var(--navy-deep);
}
.lecture-body p {
  margin: 0;
  font-size: 0.95rem;
  color: #404a60;
}

/* ---------- Audience ---------- */
.grid-2 {
  display: grid;
  gap: 40px;
  grid-template-columns: repeat(2, minmax(0,1fr));
}

/* ---------- Presenters ---------- */
.presenters {
  display: grid;
  gap: 20px;
  grid-template-columns: 1fr;
}
.presenter {
  display: grid;
  grid-template-columns: 80px 1fr;
  gap: 24px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  align-items: start;
}
.presenter-avatar {
  width: 64px; height: 64px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--navy) 0%, var(--accent) 130%);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 18px;
  letter-spacing: 0.05em;
}
.presenter-body h3 {
  font-size: 1.15rem;
  margin: 0 0 4px;
}
.presenter-aff {
  color: var(--muted);
  font-size: 0.92rem;
  margin-bottom: 12px;
}
.presenter-body p { font-size: 0.95rem; color: #2c3346; }
.links {
  list-style: none;
  padding: 0;
  margin: 14px 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.links a {
  display: inline-block;
  padding: 4px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-size: 13px;
  background: var(--bg-soft);
}
.links a:hover {
  background: var(--navy-deep);
  color: #fff;
  border-color: var(--navy-deep);
}

/* ---------- Contact ---------- */
.contact-list {
  list-style: none;
  margin: 0; padding: 0;
  display: grid;
  gap: 12px;
  grid-template-columns: repeat(3, minmax(0,1fr));
}
.contact-list li {
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 20px;
}
.contact-name {
  display: block;
  font-weight: 600;
  color: var(--navy-deep);
  margin-bottom: 4px;
  font-size: 0.95rem;
}
.contact-list a { font-size: 0.9rem; word-break: break-all; }

/* ---------- Footer ---------- */
.site-footer {
  background: var(--navy-deep);
  color: #b9c2d4;
  padding: 36px 0;
  margin-top: 0;
}
.footer-inner p { margin: 0 0 4px; font-size: 0.9rem; }
.site-footer a { color: #fff; text-decoration: underline; text-underline-offset: 3px; }
.site-footer a:hover { color: var(--gold); }
.footer-fine { color: #7d88a0; font-size: 0.82rem !important; }

/* ---------- Responsive ---------- */
@media (max-width: 880px) {
  .cards,
  .outline,
  .grid-2,
  .contact-list { grid-template-columns: 1fr; }
  .hero-meta { grid-template-columns: 1fr; }
  .section { padding: 64px 0; }
  .hero { padding: 72px 0 64px; }
}

@media (max-width: 720px) {
  .nav-toggle { display: flex; }
  .nav-list {
    display: none;
    position: absolute;
    top: 72px;
    left: 0; right: 0;
    background: #fff;
    border-bottom: 1px solid var(--line);
    flex-direction: column;
    gap: 0;
    padding: 8px 16px 16px;
  }
  .site-nav.open .nav-list { display: flex; }
  .nav-list a {
    padding: 12px 12px;
    border-bottom: 1px solid var(--line);
    border-radius: 0;
  }
  .nav-list li:last-child a { border-bottom: 0; }
  .brand-title { font-size: 13px; }
  .brand-sub { font-size: 11px; }
}

@media (max-width: 480px) {
  .presenter { grid-template-columns: 1fr; }
  .presenter-avatar { width: 56px; height: 56px; font-size: 16px; }
  .hero h1 { font-size: 1.85rem; }
}