.reading-progress {
  position: fixed;
  z-index: 9999;
  inset-block: 12vh;
  inset-inline-end: 4px;
  width: 3px;
  border-radius: 3px;
  background: rgba(170, 160, 180, .22);
  pointer-events: none;
}
.reading-progress[hidden] { display: none; }
.reading-progress::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: var(--reading-accent, #05d5f4);
  transform: scaleY(var(--reading-position, 0));
  transform-origin: top;
}