You made it to the last part of the book, well done! J.R.R. Tolkien, the author of Lord of the Rings, wrote quite a few stories that he never finished during his lifetime. These were completed by his son and published under the name Unfinished Tales.
These last two chapters are a sort of Unfinished Tales for you, the developer, to pick up and develop on your own. Each chapter contains three unfinished projects for you to pick up yourself and keep developing. They are finished in the sense that they all work: you can just type cargo run and start using them. But they are meant to be as short as possible, and that means they only have the most basic functionality. After that, it’s up to you to keep working on them if you feel like it.
These two chapters also use quite a few new crates because the crates used for command-line interfaces (CLIs) and graphical user interfaces (GUIs) are best learned through real use on a computer. The crates used in this chapter won’t work on the Playground because they require access to system resources and the ability to do things like take user input in real time and open new windows.