We want to include a less technical description of how the project is structured for people that are interested, but are less familiar with code. It will also help us work on making the project more understandable and improve our ability to explain it to others.
The app you are using is written in Kotlin, and the backend that supports it is in Rust. We had some previous experience with Android development, but are completely new to Rust.
Both are growing and used by more and move developers (stackoverflow survey) and we decided to use these languages based on reputation and oportunity to learn.
You can also take a look at the code for the android app, backend and website on Github.