hugo-theme-next/assets/css/_common/components/reading-progress.scss

@if $reading_progress_enable {
  .reading-progress-bar {
    --progress: 0;
    background: convert($reading_progress_color);
    height: convert($reading_progress_height);
    position: fixed;
    z-index: $zindex-5;

    @if $reading_progress_reversed {
      width: calc(100% - var(--progress));
    } @else {
      width: var(--progress);
    }

    @if $reading_progress_start == 'right' {
      right: 0;
    } @else {
      left: 0;
    }

    @if $reading_progress_position == 'bottom' {
      bottom: 0;
    } @else {
      top: 0;
    }
  }
}