/* ── Custom Properties ──────────────────────────────────────────── */
:root {
  /* Primary palette */
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #dbeafe;
  --color-primary-text: #ffffff;

  /* Neutrals */
  --color-gray-50: #f9fafb;
  --color-gray-100: #f3f4f6;
  --color-gray-200: #e5e7eb;
  --color-gray-300: #d1d5db;
  --color-gray-400: #9ca3af;
  --color-gray-500: #6b7280;
  --color-gray-600: #4b5563;
  --color-gray-700: #374151;
  --color-gray-800: #1f2937;
  --color-gray-900: #111827;

  /* Semantic */
  --color-bg: #f9fafb;
  --color-surface: #ffffff;
  --color-text: #1f2937;
  --color-text-secondary: #6b7280;
  --color-border: #e5e7eb;

  /* Category colors */
  --cat-relational: #2563eb;
  --cat-key-value: #15803d;
  --cat-document: #a16207;
  --cat-vector: #7c3aed;
  --cat-graph: #dc2626;
  --cat-olap: #c2410c;
  --cat-time-series: #0f766e;
  --cat-search: #db2777;
  --cat-multi-model: #4f46e5;
  --cat-mobile: #6b7280;

  /* Sizing */
  --max-width: 1280px;
  --sidebar-width: 260px;
  --card-min-width: 280px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-pill: 9999px;

  /* Shadows */
  --shadow-card: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-card-hover: 0 4px 12px rgba(0,0,0,0.1), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-focus: 0 0 0 3px rgba(37,99,235,0.25);

  /* Transitions (reduced-motion safe) */
  --transition-fast: 150ms ease;
  --transition-normal: 200ms ease;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
                 "Helvetica Neue", Arial, "Noto Sans", sans-serif,
                 "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
               "Liberation Mono", monospace;
}

/* ── Reset / Base ────────────────────────────────────────────────── */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-primary-dark);
  text-decoration: underline;
}

img, svg {
  display: block;
  max-width: 100%;
}

/* ── Skip link ────────────────────────────────────────────────────── */
.skip-link {
  position: absolute;
  top: -100%;
  left: 0.75rem;
  z-index: 1000;
  padding: 0.625rem 1.25rem;
  background: var(--color-primary);
  color: #fff;
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 0;
  outline: 2px solid var(--color-primary-dark);
  outline-offset: 2px;
}

/* ── Focus ───────────────────────────────────────────────────────── */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* Card receives visible focus when navigated via keyboard
   (cards are treated as composite widgets) */
.db-card:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-card-hover);
}

/* Filter chips: explicit focus-visible */
.filter-chip:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Nav buttons: focus-visible */
.nav-btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Compare toggle button: focus-visible */
.compare-toggle:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Tree choice buttons: focus-visible (overrides generic outline
   in favor of box-shadow to avoid clipping) */
.tree-choice-btn:focus-visible {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--shadow-focus);
}

/* Tree nav buttons: focus-visible */
.tree-back-btn:focus-visible,
.tree-skip-btn:focus-visible,
.tree-results-btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Compare remove button: focus-visible */
.compare-remove-btn:focus-visible {
  outline: 2px solid #dc2626;
  outline-offset: 1px;
}

/* Active filter pill remove button: focus-visible */
.active-filter-pill button:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 1px;
}

/* Empty / error state buttons */
.empty-state .btn:focus-visible,
.error-state .btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Back to browse button in compare */
.back-browse-btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Filter toggle button (mobile) */
.filter-toggle-btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}