My Time is a simple app, but by building it you've covered a lot of Flutter features. In particular, you've used the GridView layout—a scrollable, 2D array of widgets that you can use to show data to your users in tabular form.
You've seen ways to implement asynchronous programming with Flutter. In particular, you've used a Stream to implement the countdown for the app, and you've used a StreamBuilder to listen to the events that came from the Stream. You've seen that the Streambuilder rebuilds its children at any change of the Stream.
Then, you've used the Navigator class to show different screens to your users, through the push() and pop() methods.
Finally, you've seen that there is a simple and effective way to store data for your apps: the SharedPreferences class, from the shared_preference library. You've also seen...