/* Scroll-to-top button */
.scroll-to-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 40px;
  height: 40px;
  background-color: var(--primary-color, #111111);
  color: #ffffff;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
  box-shadow: 0 2px 5px var(--shadow-color, rgba(0, 0, 0, 0.2));
  cursor: pointer;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.3s, transform 0.3s, background-color 0.3s;
  z-index: 1000;
}

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

.scroll-to-top:hover {
  background-color: var(--accent-color, #b65333);
  transform: translateY(-3px);
  box-shadow: 0 4px 8px var(--shadow-color, rgba(0, 0, 0, 0.3));
}