:root {
  --dark: #172a3a;
  --blue: #1f6f8b;
  --teal: #2a9d8f;
  --orange: #e76f51;
  --light: #f6f9fb;
  --text: #243447;
  --muted: #607080;
  --card: #ffffff;
  --border: #d9e2ec;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
  color: var(--text);
  background: var(--light);
}

/* Homepage hero */

.hero {
  background:
    linear-gradient(rgba(19, 41, 61, 0.78), rgba(19, 41, 61, 0.78)),
    url("assets/Virus-Hannover.png");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  color: white;
  min-height: 70vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 5rem 1.5rem;
  text-align: center;
}

.hero-content {
  max-width: 960px;
  margin: 0 auto;
}

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.85rem;
  font-weight: 700;
  opacity: 0.85;
}

h1 {
  font-size: clamp(2.3rem, 6vw, 4.5rem);
  line-height: 1.05;
  margin: 0.5rem 0 1rem;
}

.subtitle {
  font-size: 1.2rem;
  max-width: 780px;
  margin: 0 auto;
  opacity: 0.95;
}

/* Top homepage details: date, venue, fee */

.hero-details {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  max-width: 960px;
  margin: 2rem auto 0;
}

.hero-details div {
  background: rgba(255, 255, 255, 0.14);
  border: 1px solid rgba(255, 255, 255, 0.24);
  border-radius: 16px;
  padding: 1rem;
}

.hero-details div:last-child {
  background: rgba(231, 111, 81, 0.32);
  border-color: rgba(255, 255, 255, 0.42);
}

.hero-details strong,
.hero-details span {
  display: block;
}

.hero-details strong {
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.8rem;
  opacity: 0.85;
}

.hero-details span {
  margin-top: 0.35rem;
  font-size: 1.1rem;
  font-weight: 700;
}

.hero-actions {
  margin-top: 2rem;
}

.small-note {
  margin-top: 1rem;
  font-size: 0.95rem;
  opacity: 0.8;
}

/* Buttons */

.button {
  display: inline-block;
  padding: 0.85rem 1.25rem;
  border-radius: 999px;
  text-decoration: none;
  font-weight: 750;
  margin: 0.3rem;
  transition: transform 0.15s ease, opacity 0.15s ease;
}

.button:hover {
  transform: translateY(-1px);
  opacity: 0.92;
}

.button.primary {
  background: var(--teal);
  color: white;
}

.button.secondary {
  background: var(--orange);
  color: white;
}

/* Navigation */

.nav {
  position: sticky;
  top: 0;
  z-index: 10;
  background: white;
  border-bottom: 1px solid var(--border);
  text-align: center;
  padding: 0.85rem 1rem;
}

.nav a {
  color: var(--dark);
  text-decoration: none;
  font-weight: 700;
  margin: 0 0.65rem;
  white-space: nowrap;
}

/* Main layout */

main {
  max-width: 960px;
  margin: 2rem auto;
  padding: 0 1rem;
}

.card {
  background: var(--card);
  padding: 1.7rem;
  margin-bottom: 1.25rem;
  border-radius: 18px;
  border: 1px solid var(--border);
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.06);
}

.card h2 {
  margin-top: 0;
  color: var(--dark);
  font-size: 1.7rem;
}

/* Important dates */

.date-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.date-grid div {
  background: #f0f5f8;
  padding: 1rem;
  border-radius: 14px;
}

.date-grid strong,
.date-grid span {
  display: block;
}

.date-grid span {
  margin-top: 0.35rem;
  color: var(--muted);
}

/* Generic grids */

.info-grid,
.feature-grid,
.programme-preview-grid,
.speaker-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.info-box,
.feature-box,
.programme-preview-box,
.speaker-card {
  background: #f0f5f8;
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1rem;
}

.info-box h3,
.feature-box h3,
.programme-preview-box h3,
.speaker-card h3 {
  margin-top: 0;
  margin-bottom: 0.4rem;
  color: var(--dark);
}

.info-box p,
.feature-box p,
.programme-preview-box p,
.speaker-card p {
  margin: 0.25rem 0;
}

.speaker-meta {
  color: var(--muted);
  font-weight: 600;
}

.speaker-session {
  margin-top: 0.6rem;
  font-size: 0.95rem;
}

.programme-preview-box ul {
  margin-bottom: 0;
  padding-left: 1.2rem;
}

/* Programme page */

.programme-session {
  margin-bottom: 1.5rem;
}

.programme-session h3 {
  margin-bottom: 0.7rem;
  color: var(--dark);
}

.programme-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 0.5rem;
}

.programme-table td {
  padding: 0.75rem;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}

.programme-table td:first-child {
  width: 150px;
  font-weight: 700;
  color: var(--blue);
  white-space: nowrap;
}

.programme-break {
  background: #f0f5f8;
  border-left: 5px solid var(--teal);
  padding: 0.85rem 1rem;
  margin: 1rem 0 1.5rem;
  border-radius: 10px;
  font-weight: 700;
}

/* Forms */

.page-header {
  background: linear-gradient(135deg, var(--dark), var(--blue));
  color: white;
  padding: 3rem 1.5rem;
  text-align: center;
}

.page-header h1 {
  margin: 0;
  font-size: clamp(2rem, 5vw, 3.5rem);
}

.page-header p {
  margin: 0.5rem 0 0;
  opacity: 0.9;
}

.form-card {
  padding: 0.5rem;
  overflow: hidden;
}

.form-card iframe {
  display: block;
  border: none;
  width: 100%;
}

/* Registration fee note inside page sections */

.fee-note {
  background: #f0f5f8;
  border-left: 4px solid var(--teal);
  padding: 0.9rem 1rem;
  border-radius: 10px;
}

/* Sponsors */

.sponsor-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}

.sponsor-card {
  background: #f6f9fb;
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1rem;
  text-align: center;
}

.sponsor-card img {
  max-width: 160px;
  max-height: 80px;
  width: 100%;
  height: 80px;
  object-fit: contain;
  margin-bottom: 0.75rem;
}

.sponsor-card h3 {
  margin: 0.4rem 0 0.2rem;
  font-size: 1rem;
  color: var(--dark);
}

.sponsor-card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

/* Footer */

footer {
  text-align: center;
  padding: 2rem 1rem;
  color: var(--muted);
}

/* Mobile layout */

@media (max-width: 850px) {
  .sponsor-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 700px) {
  .hero {
    padding: 3.5rem 1rem;
  }

  .hero-details {
    grid-template-columns: 1fr;
  }

  .nav {
    overflow-x: auto;
    text-align: left;
  }

  .date-grid,
  .info-grid,
  .feature-grid,
  .programme-preview-grid,
  .speaker-grid {
    grid-template-columns: 1fr;
  }

  .button {
    display: block;
    max-width: 280px;
    margin: 0.5rem auto;
  }

  .programme-table td {
    display: block;
    width: 100%;
    padding: 0.5rem 0.75rem;
  }

  .programme-table td:first-child {
    width: 100%;
    padding-top: 1rem;
  }
}

@media (max-width: 520px) {
  .sponsor-grid {
    grid-template-columns: 1fr;
  }
}