:root {
  --bg-body-dark: #5c768d;
  --header-light: #a0bccc;
  --salvador-blue: #0047AB;
  --bone-white: #f7f4ef;
  --border-color: #cbd5e1;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body { background-color: var(--bg-body-dark); font-family: -apple-system, sans-serif; display: flex; flex-direction: column; min-height: 100vh; }
header { background-color: var(--header-light); text-align: center; padding: 1.5rem; border-top: 4px solid var(--salvador-blue); }
.logo { font-family: "Times New Roman", Times, serif; font-size: 3.5rem; line-height: 1; color: #000; text-decoration: none; letter-spacing: -1px; white-space: nowrap; }
.logo .digital-es { font: inherit; line-height: inherit; color: #ffffff; background: none; padding: 0; border-radius: 0; display: inline; letter-spacing: inherit; margin: 0; transform: none; vertical-align: baseline; }
nav { background-color: #FFFFFF; display: flex; justify-content: center; align-items: center; gap: 1.2rem; padding: 0.85rem 1rem; border-bottom: 1px solid var(--border-color); flex-wrap: wrap; }
nav a, nav span { color: #334155; text-decoration: none; font-size: 0.9rem; font-weight: 600; }
nav a:hover { color: var(--salvador-blue); }
main { max-width: 1100px; width: 100%; margin: 2rem auto; padding: 0 1rem; flex: 1; }
.alphabet-section { background-color: #F8FAFC; border-radius: 12px; padding: 3rem 2rem; box-shadow: 0 4px 12px rgba(0,0,0,0.08); margin-bottom: 2rem; text-align: center; }
.alphabet-title { font-family: "Times New Roman", Times, serif; font-weight: bold; font-size: 1.8rem; color: #0f172a; margin-bottom: 1rem; }
.alphabet-section p { color: #475569; }
.book-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 1rem; text-align: left; }
.book-card { display: block; background-color: #F8FAFC; border: 1px solid #E2E8F0; border-radius: 12px; box-shadow: 0 4px 12px rgba(0,0,0,0.08); color: #0f172a; padding: 1rem; text-decoration: none; font-weight: 700; transition: transform 0.2s, box-shadow 0.2s; }
.book-card:hover { transform: translateY(-4px); box-shadow: 0 8px 16px rgba(0,0,0,0.15); }
.libro .autor, .autor { display: block; font-size: 0.88rem; font-weight: 400; color: #6b7280; margin-top: 4px; line-height: 1.2; }
footer { background: var(--bone-white); text-align: center; padding: 1.5rem; color: #64748b; margin-top: auto; border-top: 1px solid var(--border-color); }

@media (max-width: 600px) {
  .logo { font-size: 2.8rem; }
  .alphabet-section { padding: 2rem 1.25rem; }
  .book-grid { grid-template-columns: 1fr; }
}