/* ==========================================================================
   ENHANCEMENTS - Mejoras visuales adicionales
   ========================================================================== */

/* Botón volver arriba */
#back-to-top {
  position: fixed;
  bottom: var(--spacing-xl);
  right: var(--spacing-xl);
  width: 50px;
  height: 50px;
  border-radius: 50%;
  background-color: var(--primary-color);
  color: white;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  box-shadow: var(--shadow-lg);
  transition: all var(--transition-base);
  opacity: 0;
  visibility: hidden;
  z-index: var(--z-sticky);
}

#back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

#back-to-top:hover {
  background-color: var(--primary-dark);
  transform: translateY(-4px);
  box-shadow: var(--shadow-xl);
}

/* Efectos de carga para imágenes */
.card-image.loading {
  background: linear-gradient(90deg, var(--gray-200) 25%, var(--gray-100) 50%, var(--gray-200) 75%);
  background-size: 200% 100%;
  animation: loading 1.5s infinite;
}

@keyframes loading {
  0% {
    background-position: 200% 0;
  }
  100% {
    background-position: -200% 0;
  }
}

/* Mejoras de accesibilidad */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Enfoque accesible */
:focus-visible {
  outline: 3px solid var(--primary-color);
  outline-offset: 2px;
  border-radius: var(--border-radius-sm);
}

/* Estilos de selección de texto */
::selection {
  background-color: var(--primary-color);
  color: white;
}

.dark-mode ::selection {
  background-color: var(--accent-color);
  color: var(--gray-900);
}

/* Mejoras para impresión */
@media print {
  .footer,
  #reading-progress,
  #back-to-top {
    display: none !important;
  }
  
  body {
    color: black;
    background-color: white;
  }
  
  .card {
    box-shadow: none;
    border: 1px solid #ddd;
  }
}