The application is complete, but there are still lots of functionalities that can be added. In this application, we've seen some examples of how Kotlin can be used to simplify Android development. But there are still a lot of solutions to discover. Kotlin simplifies Android development at any level--from common operations such as listener set or view element reference, to high-level functionalities such as functional programming or collection processing.
This book cannot cover absolutely everything about Android development with Kotlin, but it has been designed to show enough to allow everyone to start their own adventure with bags of ideas and feature understanding. The next step is to open Android Studio, create your own project, and start having fun with Kotlin. A big adventure is in front of you.