[Feedback Wanted 🙏] What's a good demo app?

What makes a good demo app for you? One struggle about writing technical guidance is finding the right way to deliver the concepts. In the case of a technical tutorial, the most common way to teach is by asking readers to build something. For you, what would be that “something” that helps you learn? When is a demo app too simple or too complex?

If you were searching for how to add authentication or authorization to an app, would you prefer to be provided with a starter app to practice the security implementation or would you rather have the tutorial quickly build that basic starter app and then go into the details of the security implementation?

Thank you for any feedback on this!