The main game system works around a dependency injection framework: https://github.com/modesttree/Zenject Variables, references, and scriptable objects inspired by https://youtu.be/6vmRwLYWNRo.
Most of the scripts have a single responsibility and no circular dependencies involved, the scripts are simple enough to duplicate them and assign new variables and it should work.
WASD to move.
Move close to the NPC to interact.
Buy/Sell items with a discount.
Inventory: Switch item on drag, equip/consume on click.
Check Assets/Scripts/Installers for a quick dependencies overview.