.back-to-top {
  position: fixed;
  right: 1.5rem;
  bottom: 1.5rem;
  z-index: 250;

  display: flex;
  align-items: center;
  justify-content: center;

  width: 56px;
  height: 56px;

  border: 1px solid var(--color-border);
  border-radius: 999px;

  background-color: rgba(13, 13, 13, 0.92);
  backdrop-filter: blur(10px);

  color: var(--color-white);
  font-size: 1.4rem;
  line-height: 1;

  cursor: pointer;

  opacity: 0;
  visibility: hidden;
  transform: translateY(16px);

  transition:
    opacity var(--transition-fast),
    visibility var(--transition-fast),
    transform var(--transition-fast),
    background-color var(--transition-fast);
}

.back-to-top:hover {
  background-color: var(--color-accent);
  transform: translateY(0) scale(1.05);
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 4px;
}

@media (max-width: 768px) {
  .back-to-top {
    right: 1rem;
    bottom: 1rem;

    width: 48px;
    height: 48px;

    font-size: 1.2rem;
  }
}