#scroll-top-button-mobile {
  position: fixed;
  z-index: 99;
  right: 16px;
  bottom: 18px;
  min-width: 42px;
  min-height: 42px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 10px;
  border: 1px solid rgba(148, 163, 184, 0.22);
  background: var(--board-bg-color);
  color: var(--sec-text-color);
  box-shadow: 0 10px 26px rgba(0, 0, 0, 0.18);
  opacity: 0;
  transform: translateY(16px);
  pointer-events: none;
  transition: opacity 0.18s ease, transform 0.18s ease, background-color 0.18s ease, border-color 0.18s ease;
}

#scroll-top-button-mobile i {
  font-size: 28px;
  line-height: 1;
}

#scroll-top-button-mobile.is-visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

@media (min-width: 768px) {
  #scroll-top-button-mobile {
    display: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  #scroll-top-button-mobile {
    transition: none;
  }
}