.btn {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: none;
  background: #466aff;
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 12px rgba(70, 106, 255, 0.4);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease, transform 0.3s ease;
  z-index: 999;
}

.visible {
  opacity: 1;
  visibility: visible;
}

.btn:hover {
  transform: scale(1.1);
  box-shadow: 0 4px 16px rgba(70, 106, 255, 0.6);
}

[data-theme='dark'] .btn {
  background: #466aff;
  box-shadow: 0 2px 12px rgba(70, 106, 255, 0.3);
}

@media (max-width: 768px) {
  .btn {
    bottom: 1.2rem;
    right: 1.2rem;
    width: 40px;
    height: 40px;
  }
}
