Tutorials
The book offers a set of tutorials of how to write a game of specific genre using the engine. Every tutorial starts from mild difficulty and keep increasing the difficulty until the end. All tutorials are very well-structured, and you shouldn't be able to lost in them.
Source code for every tutorial can be found here.
All tutorials in the book are ordered from simplest to hardest, and each chapter in each tutorial is also ordered in the same way.
Code snippets in all tutorials does not include required imports, you should use a good IDE (Visual Studio Code + rust-analyzer, IntelliJ IDEA + Rust Plugin, RustRover, etc.) that can import all missing stuff for your project. Alternatively, you can always look at the source code of all tutorials in the link above. This is intentional, to reduce the size of all tutorials; to prevent them from bloating with useless information.