Target Sizes and Contrast

- Never shrink interactive controls below the minimum threshold on touch devices.

## Color Contrast Ratios (WCAG 2.1 AA)

- **Normal Text (< 18 pt or < 14 pt bold)**: Contrast ratio must be at least **4.5:1** against the background.
- **Large Text (≥ 18 pt or ≥ 14 pt bold)**: Contrast ratio must be at least **3.0:1** against the background.
- **UI Components and Icons**: Functional icons and borders must have at least **3.0:1** contrast against adjacent colors.
- **Color Blindness / Dual Encoding**: Never convey critical state or instructions with color alone. Pair color cues with text labels, distinct icons, or patterned styling.

## Text Scaling and Dynamic Type

- Support `TextScaler` scaling up to 200% without clipping, truncation, or layout overflow.
- Avoid fixed heights on containers containing text (`SizedBox(height: 50)`).
- Allow text to wrap or use `SingleChildScrollView` / `Expanded` when large text scale is active.
- Ensure buttons and list tiles expand vertically when text scales.

## Testing Guidelines

Run Flutter's built-in accessibility matchers in widget tests:
```dart
testWidgets('A11y guidelines check', (tester) async {
  final handle = tester.ensureSemantics();
  await tester.pumpWidget(const MyApp());
  await expectLater(tester, meetsGuideline(textContrastGuideline));
  await expectLater(tester, meetsGuideline(androidTapTargetGuideline));
  handle.dispose();
});