:root {
  --bg: #ffffff;
  --bg-soft: #f4f9fc;
  --text: #1b3f61;
  --title: #0f3557;
  --muted: #5e7a91;
  --primary: #1c76bc;
  --secondary: #28a7df;
  --line: rgba(15, 53, 87, 0.12);
  --shadow: 0 14px 28px rgba(15, 53, 87, 0.07);
  --radius-lg: 22px;
  --radius-md: 16px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Avenir Next", "Segoe UI", Helvetica, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
}

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

a {
  color: inherit;
  text-decoration: none;
}

a:hover {
  color: var(--primary);
}

.container {
  width: min(1340px, 92vw);
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
}

.nav {
  min-height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.brand {
  font-weight: 700;
  color: var(--title);
  letter-spacing: 0.02em;
  white-space: nowrap;
  flex: 0 0 auto;
}

.nav nav {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: nowrap;
  justify-content: flex-end;
  min-width: 0;
  flex: 1 1 auto;
  overflow-x: auto;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.nav nav::-webkit-scrollbar {
  display: none;
}

.nav nav a {
  color: var(--muted);
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid transparent;
  transition: all 0.2s ease;
  white-space: nowrap;
  font-size: 0.9rem;
}

.nav nav a:hover {
  border-color: rgba(28, 118, 188, 0.22);
  background: rgba(28, 118, 188, 0.07);
  color: var(--title);
}

.hero {
  padding: 56px 0 42px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 28px;
  align-items: center;
}

.eyebrow {
  margin: 0 0 12px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--primary);
  font-weight: 700;
  font-size: 0.82rem;
}

h1,
h2,
h3 {
  margin: 0;
  color: var(--title);
  line-height: 1.2;
}

h1 {
  font-size: clamp(2rem, 4.5vw, 3.35rem);
  letter-spacing: -0.02em;
}

h2 {
  font-size: clamp(1.55rem, 3.2vw, 2.2rem);
}

h3 {
  font-size: 1.2rem;
}

.subtitle {
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 1.08rem;
}

.meta {
  margin: 22px 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.meta span {
  padding: 8px 14px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: #fff;
  box-shadow: var(--shadow);
  font-size: 0.94rem;
  color: var(--title);
}

.actions {
  margin-top: 24px;
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn {
  padding: 10px 18px;
  border-radius: 999px;
  font-weight: 650;
  transition: transform 0.2s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  background: var(--title);
  color: #fff;
}

.btn-secondary {
  border: 1px solid rgba(28, 118, 188, 0.24);
  background: rgba(28, 118, 188, 0.06);
  color: var(--title);
}

.hero-image-card {
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 18px;
  background: linear-gradient(180deg, rgba(244, 249, 252, 0.9), #ffffff);
  box-shadow: var(--shadow);
}

.section {
  padding: 72px 0;
}

.muted-bg,
.organizer-bg {
  background: var(--bg-soft);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.section-intro {
  margin: 14px 0 0;
  color: var(--muted);
}

.about-intro {
  margin: 14px 0 0;
  color: var(--muted);
  max-width: 920px;
}

.topic-grid {
  margin-top: 22px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.topic-card {
  padding: 18px;
}

.topic-card h3 {
  font-size: 1.08rem;
}

.topic-list {
  margin: 12px 0 0;
  padding-left: 18px;
  color: var(--muted);
}

.topic-list li + li {
  margin-top: 8px;
}

.tags {
  margin: 20px 0 0;
  padding: 0;
  list-style: none;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.tags li {
  padding: 8px 14px;
  border: 1px solid rgba(28, 118, 188, 0.24);
  border-radius: 999px;
  background: rgba(28, 118, 188, 0.05);
  color: var(--title);
  font-weight: 600;
}

.date-grid {
  margin-top: 22px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.date-card {
  padding: 16px 18px;
}

.date-label {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.date-value {
  margin: 6px 0 0;
  color: var(--title);
  font-weight: 650;
}

.challenge-grid {
  margin-top: 28px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}

.card {
  border-radius: var(--radius-md);
  border: 1px solid var(--line);
  background: #fff;
  box-shadow: var(--shadow);
}

.challenge-card {
  padding: 22px;
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 20px;
  align-items: stretch;
}

.challenge-card p {
  margin: 12px 0 0;
  color: var(--muted);
}

.challenge-media {
  border-radius: 14px;
  border: 1px solid var(--line);
  overflow: hidden;
  background: #fff;
}

.challenge-media img {
  width: 100%;
  height: 100%;
  min-height: 180px;
  object-fit: cover;
}

.challenge-content {
  display: flex;
  flex-direction: column;
}

.challenge-card .dataset {
  color: var(--title);
  font-weight: 650;
}

.schedule-wrap {
  margin-top: 22px;
  overflow-x: auto;
}

.schedule-table {
  width: 100%;
  border-collapse: collapse;
}

.schedule-table th,
.schedule-table td {
  padding: 12px 14px;
  text-align: left;
  border-bottom: 1px solid var(--line);
}

.schedule-table thead th {
  background: rgba(28, 118, 188, 0.08);
  color: var(--title);
  font-weight: 700;
}

.schedule-table tbody tr:last-child td {
  border-bottom: none;
}

.schedule-table tbody td:first-child {
  white-space: nowrap;
  color: var(--title);
  font-weight: 600;
}

.links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.links a,
.speaker-actions a {
  padding: 7px 12px;
  border-radius: 999px;
  border: 1px solid rgba(28, 118, 188, 0.2);
  background: rgba(28, 118, 188, 0.06);
  font-size: 0.9rem;
  font-weight: 600;
}

.speaker-list {
  margin-top: 28px;
  display: grid;
  gap: 16px;
}

.speaker-card {
  padding: 18px;
  display: grid;
  grid-template-columns: 148px 1fr;
  gap: 18px;
  align-items: start;
}

.speaker-card img {
  width: 148px;
  height: 148px;
  object-fit: cover;
  border-radius: 16px;
  border: 1px solid var(--line);
}

.affiliation {
  margin: 6px 0 0;
  color: var(--muted);
}

.talk-title {
  margin: 10px 0 0;
}

.speaker-actions {
  margin: 12px 0 0;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.organizer-grid {
  margin-top: 26px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 22px 16px;
}

.organizer {
  text-align: center;
}

.organizer a {
  min-height: 210px;
  padding: 14px 10px;
  border-radius: 14px;
  border: 1px solid transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  transition: all 0.2s ease;
}

.organizer a:hover {
  border-color: rgba(28, 118, 188, 0.2);
  background: rgba(255, 255, 255, 0.8);
  box-shadow: 0 10px 20px rgba(15, 53, 87, 0.06);
}

.organizer img {
  width: 112px;
  height: 112px;
  margin: 0 auto;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid #fff;
  box-shadow:
    0 0 0 1px rgba(28, 118, 188, 0.2),
    0 10px 24px rgba(15, 53, 87, 0.08);
}

.organizer p {
  margin: 12px 0 0;
}

.organizer-name {
  color: var(--title);
  font-weight: 600;
}

.organizer-affiliation {
  margin-top: 4px;
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.35;
}

.sponsor-grid {
  margin-top: 24px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.sponsor-card {
  min-height: 170px;
}

.sponsor-card a {
  height: 100%;
  padding: 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
}

.sponsor-card img {
  max-height: 64px;
  width: auto;
  max-width: 80%;
  object-fit: contain;
}

.sponsor-card p {
  margin: 0;
  color: var(--title);
  font-weight: 600;
}

.sponsor-dark {
  background: #153d61;
  border-color: rgba(21, 61, 97, 0.7);
}

.sponsor-dark p {
  color: #ffffff;
}

.related-list {
  margin: 22px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 10px;
}

.related-item {
  padding: 14px 16px;
}

.related-item a {
  display: block;
  color: var(--title);
  font-weight: 600;
}

.site-footer {
  padding: 24px 0 34px;
  background: #fff;
}

.footer-inner {
  border-top: 1px solid var(--line);
  padding-top: 20px;
  display: flex;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
  color: var(--muted);
}

@media (max-width: 1000px) {
  .hero-grid {
    grid-template-columns: 1fr;
  }

  .topic-grid {
    grid-template-columns: 1fr;
  }

  .date-grid {
    grid-template-columns: 1fr;
  }

  .challenge-card {
    grid-template-columns: 1fr;
  }

  .challenge-media img {
    min-height: 220px;
  }
}

@media (max-width: 760px) {
  .section {
    padding: 56px 0;
  }

  .nav {
    padding: 12px 0;
    flex-direction: column;
    align-items: flex-start;
  }

  .speaker-card {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .speaker-card img {
    margin: 0 auto;
  }

  .speaker-actions {
    justify-content: center;
  }

  .organizer-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .sponsor-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 460px) {
  .organizer-grid {
    grid-template-columns: 1fr;
  }
}