Castagne's main goal is to be a flexible engine for making various types of fighting games. It tries to impose as little restrictions as possible, while trying to help the user by reducing their workload through good tools.
In order to achieve this, Castagne is composed of three main parts:
These are the parts most users are going to interact with. Castagne does the link between the behavior you want, its modules, and the underlying Godot engine so that you may focus as much as possible on the game itself, while online or optimization are taken care of as much as possible behind the scenes.
To give you an intuition of Castagne's commitment to flexibility, very few assumptions are built into the engine, and all functionality is done through modules, meaning you can write another physics system and have it still work with Castagne. All the actual behavior is written in the fighter scripts, meaning that if you don't like how the movement works, or how rounds end, you can change it, and all of that is readable directly from the editor. This also means that, by design, Castagne is made to be able to handle different types of games beyond regular fighting games.
If you want to learn more about those subparts, you may want to read these parts once you're done with the tutorial: