/* back-to-top component */
.back-to-top {
  position: fixed;
  right: 16px;
  bottom: calc(22px + env(safe-area-inset-bottom)); /* default, will be adjusted by JS if chat exists */
  width: 48px;
  height: 48px;
  border-radius: 50%;
  /* 60% opacity background */
  background: rgba(255,138,0,0.6);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 6px 18px rgba(0,0,0,0.12);
  border: none;
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transform: translateY(6px);
  transition: opacity .2s ease, transform .2s ease, box-shadow .12s ease;
  z-index: 1000;
}

.back-to-top svg { width: 60%; height: 60%; display:block; }

.back-to-top.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: none;
}

.back-to-top:hover,
.back-to-top:focus {
  transform: translateY(-2px) scale(1.04);
  box-shadow: 0 10px 25px rgba(0,0,0,0.18);
  outline: none;
}

.back-to-top:focus-visible {
  box-shadow: 0 0 0 3px rgba(255,138,0,0.18), 0 10px 25px rgba(0,0,0,0.18);
}

@media (max-width: 375px) {
  .back-to-top { right: 12px; bottom: calc(80px + env(safe-area-inset-bottom)); width: 44px; height: 44px; }
  .back-to-top svg { width: 20px; height: 20px; }
}

@media (prefers-reduced-motion: reduce) {
  .back-to-top, .back-to-top.is-visible { transition: none; }
}