Great job demonstrating how SOLID principles can be effectively applied in a Flutter context! The way you structured the notification system using abstraction and clean separation of responsibilities makes the concepts easy to follow and directly applicable. The real-world example with Notifier, EmailNotifier, and SMSNotifier is especially helpful for understanding Dependency Inversion and Interface Segregation. This kind of architecture lays the groundwork for scalable and testable Flutter apps. Thanks for sharing such a practical walkthrough!