App Interface Guideline: Feedback — Loading Indicators. Keywords: activity indicator skeleton. Platform: iOS/Android/React Native. Description: Show visible feedback during network operations. Do: Use ActivityIndicator or skeleton for >300ms operations. Don't: Leave button and screen frozen. Good Example: {loading ? <ActivityIndicator /> : <Button title="Save" />}. Bad Example:  "<Button title=""Save"" onPress={submit} /> // no loading". Severity: High.