:root {
  font-family: 'Segoe UI', system-ui, -apple-system, BlinkMacSystemFont, 'Helvetica Neue', sans-serif;
  color: #1f2933;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background: linear-gradient(135deg, #fdf0d5, #f9f5ff);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
}

.landing-container {
  background: #ffffff;
  border-radius: 18px;
  box-shadow: 0 30px 60px rgba(15, 23, 42, 0.15);
  width: min(960px, 100%);
  display: grid;
  gap: 1.5rem;
  padding: 2.5rem;
}

.sponsor-row {
  background-color: #ff8a00;
  color: #1f2933;
  border-radius: 12px;
  padding: 1rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-weight: 600;
  transition: background-color 0.3s ease;
}

.sponsor-row button {
  border: none;
  background: #1f2933;
  color: #ffffff;
  padding: 0.5rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  font-weight: 600;
  transition: transform 0.2s ease, opacity 0.2s ease;
}

.sponsor-row button:hover {
  transform: translateY(-1px);
  opacity: 0.85;
}

.sponsor-row.toggled {
  background-color: #E20074;
  color: #fff;
}

.section-heading h1 {
  font-size: 1.6rem;
  letter-spacing: 0.02em;
  color: #0f172a;
  text-align: center;
}

.workbook-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.5rem;
}

.workbook-card {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
  text-align: center;
  align-items: center;
}

.workbook-card a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  min-height: 220px;
  padding: 1rem;
  border-radius: 16px;
  background-color: #fff;
  overflow: hidden;
  box-shadow: 0 15px 35px rgba(15, 23, 42, 0.15);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.workbook-card a:hover,
.workbook-card a:focus-visible {
  transform: translateY(-6px);
  box-shadow: 0 20px 45px rgba(15, 23, 42, 0.25);
}

.workbook-card img {
  display: block;
  width: 100%;
  aspect-ratio: 1 / 1;
  max-height: 25vh;
  max-width: 25vh;
  object-fit: cover;
  margin: 0 auto;
}

.workbook-card figcaption {
  font-size: 0.95rem;
  color: #475467;
  line-height: 1.4;
}

@media (max-width: 640px) {
  .landing-container {
    padding: 1.5rem;
  }

  .sponsor-row {
    flex-direction: column;
    gap: 0.75rem;
    text-align: center;
  }
}