#scrollTopBtn {
  position: fixed;
  right: 20px;
  bottom: 20px;
  width: 44px;
  height: 44px;
  background: #3a3a3a;
  border: 1px solid transparent;
  border-radius: 2px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(10px) scale(0.96);
  transition: opacity 0.45s ease, transform 0.45s ease, background-color 0.25s ease, border-color 0.25s ease, visibility 0s linear 0.45s;
  box-shadow: none;
}

#scrollTopBtn.is-visible {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateY(0) scale(1);
  animation: stt-pop 260ms ease;
  transition-delay: 0s;
}

#scrollTopBtn svg {
  width: 12px;
  height: 18px;
  fill: #ffffff;
  transition: fill 0.2s ease, transform 0.2s ease;
}

#scrollTopBtn:hover {
  background: #ffffff;
  border-color: #2a2a2a;
}

#scrollTopBtn:hover svg {
  fill: #1a1a1a;
  transform: translateY(-1px);
}

@keyframes stt-pop {
  0% {
    opacity: 0;
    transform: translateY(12px) scale(0.92);
  }
  100% {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

@media (max-width: 600px) {
  #scrollTopBtn {
    right: 16px;
    bottom: 16px;
    width: 40px;
    height: 40px;
  }

  #scrollTopBtn svg {
    width: 11px;
    height: 16px;
  }
}