.contenido {
  max-width: 800px;
  margin: 2rem auto;
  padding: 1rem;
  font-family: 'Arial', sans-serif;
  line-height: 1.6;
  color: #333;
  background-color: rgba(255, 255, 255, 0.85);
  border-radius: 8px;
    margin-top: var(--nav-h); /* pushes content below top bar */

}