.scroll-rail {
  position: fixed;
  right: 20px;
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  margin: 5px 0;
  background: rgba(0, 0, 0, 0.6);
  color: #fff;
  text-decoration: none;
  border-radius: 50%;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
  transition: opacity 0.2s ease, background 0.2s ease;
}

.scroll-rail.hidden {
  opacity: 0;
  pointer-events: none;
}

.scroll-rail:hover {
  background: rgba(0, 0, 0, 0.8);
}

.scroll-rail.rail-up {
  bottom: 70px;
}

.scroll-rail.rail-down {
  bottom: 20px;
}