How should you design a custom widget's public constructor parameters to make it flexible and genuinely reusable across many different contexts, without becoming overly complicated?

Designing a genuinely reusable custom widget involves carefully thinking through which specific aspects of its appearance and behavior actually need to be customizable by whoever uses it, exposing those specific aspects as clearly named constructor parameters with sensible default values where a reasonable default genuinely exists, while deliberately avoiding exposing every single conceivable internal detail as a separate parameter, since a widget with an excessive number of parameters becomes confusing and genuinely difficult to actually use correctly, so striking the right balance between flexibility and simplicity is an important, deliberate design consideration.

class AppCard extends StatelessWidget {
  final Widget child;
  final EdgeInsets padding;
  const AppCard({required this.child, this.padding = const EdgeInsets.all(16)});
}