/* ===================================
   SCROLL TO TOP BUTTON
   =================================== */

#scrollToTopBtn {
  position: fixed;
  right: var(--space-5);
  bottom: var(--space-5);
  z-index: 1000;
  width: var(--space-12);
  height: var(--space-12);
  background-color: var(--color-firmware-primary);
  color: var(--text-inverse);
  border: none;
  border-radius: var(--radius-full);
  box-shadow: var(--shadow-md);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  font-size: var(--font-size-xl);
  line-height: 1;
  cursor: pointer;
  font-family: inherit;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  min-height: 44px;
  min-width: 44px;
  
  /* Animaciones de entrada/salida */
  opacity: 0;
  transform: translateY(20px) scale(0.8) translateZ(0);
  pointer-events: none;
  visibility: hidden;
  
  /* Transiciones */
  transition: opacity var(--transition-normal),
              transform var(--transition-normal),
              visibility var(--transition-normal),
              background-color var(--transition-normal),
              box-shadow var(--transition-normal);
}

/* Estado visible */
#scrollToTopBtn.scroll-visible {
  opacity: 1;
  transform: translateY(0) scale(1) translateZ(0);
  pointer-events: auto;
  visibility: visible;
}

/* Estado activo durante scroll */
#scrollToTopBtn.scroll-active {
  transform: translateY(0) scale(0.95) translateZ(0);
}

/* Estados disabled */
#scrollToTopBtn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

/* Loading state */
#scrollToTopBtn.loading {
  color: transparent;
  position: relative;
}

#scrollToTopBtn.loading::after {
  content: "";
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 16px;
  height: 16px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-top: 2px solid currentColor;
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% { transform: translate(-50%, -50%) rotate(0deg); }
  100% { transform: translate(-50%, -50%) rotate(360deg); }
}

/* Hover solo en dispositivos apropiados */
@media (hover: hover) and (pointer: fine) {
  #scrollToTopBtn:hover {
    background-color: var(--color-firmware-primary);
    box-shadow: var(--shadow-lg);
    transform: translateY(-3px) scale(1.05) translateZ(0);
  }
  
  #scrollToTopBtn.scroll-visible:hover {
    transform: translateY(-3px) scale(1.05) translateZ(0);
  }
}

#scrollToTopBtn:focus-visible {
  background-color: var(--color-firmware-primary);
  box-shadow: var(--shadow-lg), var(--focus-ring);
  transform: translateY(-3px) scale(1.05) translateZ(0);
  outline: 2px solid var(--border-focus);
  outline-offset: 2px;
}

#scrollToTopBtn.scroll-visible:focus-visible {
  transform: translateY(-3px) scale(1.05) translateZ(0);
}

#scrollToTopBtn:active {
  transform: translateY(-1px) scale(0.95) translateZ(0);
  box-shadow: var(--shadow-sm);
}

/* Sombras específicas */
#scrollToTopBtn {
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.2);
}

@media (hover: hover) and (pointer: fine) {
  #scrollToTopBtn:hover {
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.35), 0 4px 6px -4px rgba(0, 0, 0, 0.25);
  }
}

#scrollToTopBtn:focus-visible {
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.35), 0 4px 6px -4px rgba(0, 0, 0, 0.25), var(--focus-ring);
}

#scrollToTopBtn:active {
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.25), 0 1px 2px -1px rgba(0, 0, 0, 0.2);
}

/* ===================================
   RESPONSIVE DESIGN
   =================================== */

/* Tablet */
@media (max-width: 768px) {
  #scrollToTopBtn {
    right: calc(var(--space-4) + env(safe-area-inset-right, 0));
    bottom: calc(var(--space-4) + env(safe-area-inset-bottom, 0));
    width: var(--space-10);
    height: var(--space-10);
    font-size: var(--font-size-lg);
    min-height: 44px;
    min-width: 44px;
    transform: translateY(15px) scale(0.9) translateZ(0);
  }
  
  #scrollToTopBtn.scroll-visible {
    transform: translateY(0) scale(1) translateZ(0);
  }
}

/* Mobile */
@media (max-width: 480px) {
  #scrollToTopBtn {
    right: calc(var(--space-3) + env(safe-area-inset-right, 0));
    bottom: calc(var(--space-3) + env(safe-area-inset-bottom, 0));
    width: var(--space-10);
    height: var(--space-10);
    font-size: var(--font-size-base);
    min-height: 40px;
    min-width: 40px;
    transform: translateY(12px) scale(0.9) translateZ(0);
  }
  
  #scrollToTopBtn.scroll-visible {
    transform: translateY(0) scale(1) translateZ(0);
  }
}

/* Small Mobile */
@media (max-width: 360px) and (min-width: 321px) {
  #scrollToTopBtn {
    right: calc(var(--space-3) + env(safe-area-inset-right, 0));
    bottom: calc(var(--space-3) + env(safe-area-inset-bottom, 0));
    width: calc(var(--space-10) * 0.9);
    height: calc(var(--space-10) * 0.9);
    font-size: calc(var(--font-size-base) * 0.9);
    min-height: 36px;
    min-width: 36px;
    transform: translateY(10px) scale(0.9) translateZ(0);
  }
  
  #scrollToTopBtn.scroll-visible {
    transform: translateY(0) scale(1) translateZ(0);
  }
}

/* Very Small Mobile */
@media (max-width: 320px) {
  #scrollToTopBtn {
    right: calc(var(--space-2) + env(safe-area-inset-right, 0));
    bottom: calc(var(--space-2) + env(safe-area-inset-bottom, 0));
    width: calc(var(--space-8));
    height: calc(var(--space-8));
    font-size: calc(var(--font-size-sm));
    min-height: 32px;
    min-width: 32px;
    transform: translateY(8px) scale(0.85) translateZ(0);
  }
  
  #scrollToTopBtn.scroll-visible {
    transform: translateY(0) scale(1) translateZ(0);
  }
}

/* ===================================
   DARK THEME
   =================================== */

[data-theme="dark"] #scrollToTopBtn {
  box-shadow: var(--shadow-md);
}

[data-theme="dark"] #scrollToTopBtn:hover {
  box-shadow: var(--shadow-lg);
}

[data-theme="dark"] #scrollToTopBtn:focus-visible {
  box-shadow: var(--shadow-lg), var(--focus-ring);
}

[data-theme="dark"] #scrollToTopBtn:active {
  box-shadow: var(--shadow-sm);
}

[data-theme="dark"] #scrollToTopBtn.loading::after {
  border-color: rgba(255, 255, 255, 0.3);
  border-top-color: currentColor;
}

/* ===================================
   ACCESSIBILITY & PERFORMANCE
   =================================== */

/* Versión más suave para usuarios sensibles al movimiento */
@media (prefers-reduced-motion: reduce) {
  #scrollToTopBtn {
    transform: translateZ(0);
    transition: opacity var(--transition-normal),
                visibility var(--transition-normal),
                background-color var(--transition-normal),
                box-shadow var(--transition-normal);
  }
  
  #scrollToTopBtn.scroll-visible {
    transform: translateZ(0);
  }
  
  #scrollToTopBtn:hover,
  #scrollToTopBtn:focus-visible,
  #scrollToTopBtn:active {
    transform: translateZ(0);
  }
  
  #scrollToTopBtn.loading::after {
    animation: none;
  }
}

@media (prefers-contrast: high) {
  #scrollToTopBtn {
    border: 2px solid var(--text-inverse);
    box-shadow: var(--shadow-xl), 0 0 0 1px var(--border-primary);
  }
  
  #scrollToTopBtn:focus-visible {
    outline-width: 3px;
    border-width: 3px;
  }
}