/* ============================================================================
   Burton v7 — Reading progress
   ----------------------------------------------------------------------------
   Thin progress rail at the top of the viewport on single articles.
   Updated by main.js as the reader scrolls. Gracefully hidden when JS is
   disabled (no default fill).
   ========================================================================= */

.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: transparent;
  z-index: calc(var(--z-header) + 1);
  pointer-events: none;
}

.reading-progress__fill {
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--color-accent) 0%, #5EEAD4 100%);
  transition: width 80ms linear;
  transform-origin: left;
  box-shadow: 0 0 8px rgba(6, 182, 212, 0.3);
}

/* When the header becomes sticky (on scroll), the progress bar slides beneath it. */
body.is-scrolled .reading-progress {
  top: 64px;
}