/* ============================================================================
   Accessibility Add-On Layer
   WCAG AAA enhancements layered on top of style.css
   ============================================================================ */

:root {
  --a11y-focus-color: #000000;
}

/* In dark mode a black ring disappears into the background, so flip it to
   white — still distinct from the lighter blue accent thanks to the offset. */
:root[data-theme="dark"] {
  --a11y-focus-color: #ffffff;
}

/* Skip to main content link - moved off-screen until focused. Offset
   horizontally rather than with a height-matched negative top, so it can't
   leave a sliver visible if padding/border/line-height change. */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  background: var(--bg);
  color: var(--fg);
  padding: 0.6rem 1rem;
  border: 2px solid var(--a11y-focus-color);
  border-radius: 4px;
  text-decoration: none;
  font-weight: 700;
}
.skip-link:focus {
  left: 0.5rem;
  top: 0.5rem;
}

/* Focus indicator: solid black, distinct from the accent blue used by
   links/buttons so the ring never blends into the element it outlines. */
:focus-visible {
  outline: 3px solid var(--a11y-focus-color);
  outline-offset: 2px;
}

/* Current page in primary nav: relies on more than color alone */
.site-header nav a[aria-current="page"] {
  text-decoration: underline;
  text-underline-offset: 0.25rem;
  font-weight: 700;
}

/* Respect reduced-motion preference */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Forced/high-contrast mode: thicken borders and underlines */
@media (prefers-contrast: more) {
  a { text-decoration-thickness: 2px; }
  .site-header, .site-footer, .page-nav { border-width: 2px; }
  article.note th, article.note td { border-width: 2px; }
}

/* Print: show link destinations, hide the skip link */
@media print {
  a { text-decoration: underline; }
  a[href^="http"]::after { content: " (" attr(href) ")"; }
  .skip-link { display: none; }
}

/* Display settings toolbar: collapsed to a small toggle button by default so
   it never sits on top of page content; the panel only opens on demand. */
.a11y-toolbar {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  z-index: 200;
  font-size: 0.8rem;
}
.a11y-toolbar__toggle {
  min-width: 2.75rem;
  min-height: 2.75rem;
  padding: 0.4rem 0.6rem;
  border: 2px solid var(--fg);
  border-radius: 50%;
  background: var(--bg);
  color: var(--fg);
  font: inherit;
  font-weight: 700;
  font-size: 1rem;
  cursor: pointer;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}
.a11y-toolbar__toggle[aria-expanded="true"] {
  background: var(--fg);
  color: var(--bg);
}
.a11y-toolbar__panel {
  position: absolute;
  right: 0;
  bottom: calc(100% + 0.5rem);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  align-items: flex-start;
  background: var(--bg);
  color: var(--fg);
  border: 2px solid var(--fg);
  border-radius: 8px;
  padding: 0.75rem;
  white-space: nowrap;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}
/* The [hidden] attribute loses to the class's `display: flex` above unless
   restated here — author CSS always beats the UA stylesheet's [hidden] rule. */
.a11y-toolbar__panel[hidden] {
  display: none;
}
.a11y-toolbar__label {
  font-weight: 700;
}
.a11y-toolbar__group {
  display: flex;
  gap: 0.3rem;
}
.a11y-toolbar__btn {
  min-width: 2.25rem;
  min-height: 2.25rem;
  padding: 0.25rem 0.5rem;
  border: 2px solid var(--fg);
  border-radius: 4px;
  background: var(--bg);
  color: var(--fg);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}
.a11y-toolbar__btn[aria-pressed="true"] {
  background: var(--fg);
  color: var(--bg);
}

/* Visually hide content but keep it available to screen readers */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}