BottomNav.css

/* ─── Mobile-first bottom navigation ─────────────────────────────────────────
 *
 * Design tokens from `src/index.css` and `src/utils/tokens.ts`.
 * Responsive: hidden above 768 px (`--bp-mobile`), fixed to viewport bottom.
 *
 * Accessibility:
 * - All touch targets ≥ 44 × 44 px (WCAG 2.5.5).
 * - Active state uses colour + top-border + icon weight (not colour alone).
 * - Focus-visible ring uses the shared `--focus-ring-color` token.
 * - `aria-current="page"` is set on the active link by NavLink.
 *
 * Reduced motion:
 * - The slide-up entrance animation is suppressed under
 *   `@media (prefers-reduced-motion: reduce)` and
 *   `[data-motion="reduced"]`.
 */

/* ── Config ──────────────────────────────────────────────────────────────── */

:root {
  --bottom-nav-height: 64px;
  --bottom-nav-bg: var(--surface, #161b22);
  --bottom-nav-border: var(--border, #30363d);
  --bottom-nav-accent: var(--accent, #58a6ff);
  --bottom-nav-text: var(--muted, #8b949e);
  --bottom-nav-text-active: var(--text, #e6edf3);
}

/* ── Nav bar ─────────────────────────────────────────────────────────────── */

.bottom-nav {
  /* hidden on desktop by default; shown via media query */
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 900;
  height: var(--bottom-nav-height);
  padding: 0 env(safe-area-inset-right, 0) env(safe-area-inset-bottom, 0) env(safe-area-inset-left, 0);
  background: var(--bottom-nav-bg);
  border-top: 1px solid var(--bottom-nav-border);
  box-shadow: 0 -2px 12px rgba(0, 0, 0, 0.25);

  /* Flex layout for evenly spaced items */
  display: flex;
  align-items: stretch;
  justify-content: space-around;

  /* Entrance animation */
  animation: bottom-nav-enter 0.3s ease-out both;
}

/* Show only on viewports ≤ 768 px */
@media (min-width: 769px) {
  .bottom-nav {
    display: none !important;
  }
}

/* ── Nav link ────────────────────────────────────────────────────────────── */

.bottom-nav__link {
  flex: 1 1 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  min-height: 44px;               /* WCAG 2.5.5 touch target */
  min-width: 44px;
  padding: 4px 6px;
  text-decoration: none;
  color: var(--bottom-nav-text);
  border: none;
  background: transparent;
  cursor: pointer;
  position: relative;              /* positioning context for the active ::before indicator */
  border-radius: 0;
  transition: color 0.2s ease, background 0.2s ease;
  -webkit-tap-highlight-color: transparent;
}

.bottom-nav__link:hover {
  color: var(--bottom-nav-text-active);
  background: rgba(88, 166, 255, 0.06);
}

.bottom-nav__link:active {
  transform: translateY(1px);
}

/* Focus ring — matches the shared .focus-ring pattern */
.bottom-nav__link:focus-visible {
  outline: 2px solid var(--focus-ring-color, var(--accent, #58a6ff));
  outline-offset: -3px;           /* inset so it's visible inside the bar */
  border-radius: 4px;
}

/* ── Active state ────────────────────────────────────────────────────────── */

.bottom-nav__link--active {
  color: var(--bottom-nav-accent);
}

.bottom-nav__link--active::before {
  content: '';
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 24px;
  height: 2px;
  background: var(--bottom-nav-accent);
  border-radius: 0 0 2px 2px;
}

/* ── Icon ────────────────────────────────────────────────────────────────── */

.bottom-nav__icon {
  display: block;
  flex-shrink: 0;
  transition: stroke-width 0.2s ease;
}

/* ── Label ───────────────────────────────────────────────────────────────── */

.bottom-nav__label {
  font-size: 0.65rem;
  font-weight: 500;
  line-height: 1.2;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

/* ── Animation ────────────────────────────────────────────────────────────── */

@keyframes bottom-nav-enter {
  from {
    transform: translateY(100%);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

/* ── Reduced motion ──────────────────────────────────────────────────────── */

@media (prefers-reduced-motion: reduce) {
  .bottom-nav {
    animation: none;
  }

  .bottom-nav__link {
    transition: none;
  }

  .bottom-nav__icon {
    transition: none;
  }
}

/* Reduced Motion Override (set via ReducedMotionContext) */
[data-motion="reduced"] .bottom-nav {
  animation: none;
}

[data-motion="reduced"] .bottom-nav__link {
  transition: none;
}

[data-motion="reduced"] .bottom-nav__icon {
  transition: none;
}

/* ── High contrast override ──────────────────────────────────────────────── */

[data-contrast="high"] .bottom-nav {
  border-top-width: 2px;
  border-top-color: var(--border, #ffffff);
  box-shadow: none;
}

[data-contrast="high"] .bottom-nav__link--active::before {
  height: 3px;
  background: var(--accent, #7dd3fc);
}

/* ── Forced-colours mode (Windows High Contrast) ─────────────────────────── */

@media (forced-colors: active) {
  .bottom-nav {
    border-top: 2px solid ButtonText;
  }

  .bottom-nav__link--active::before {
    background: Highlight;
  }
}

/* ── Compact screens (≤ 480 px) — hide labels, show only icons ──────────── */

@media (max-width: 480px) {
  .bottom-nav__label {
    display: none;
  }

  .bottom-nav__link {
    gap: 0;
  }
}

/* ── Landscape phones ────────────────────────────────────────────────────── */

@media (max-height: 480px) and (orientation: landscape) {
  :root {
    --bottom-nav-height: 52px;
  }

  .bottom-nav__link {
    flex-direction: row;
    gap: 4px;
    min-height: 40px;
  }

  .bottom-nav__label {
    display: inline;
    font-size: 0.7rem;
  }
}