I developed this sudoku in a week as a technical test to enter HomaGames. The key points were the UI, the generation algorithm for the matrices, and the tests. They did not ask me for test cases but I added them as my demonstration of knowledge about Test Driven Development and Unit Tests.
Use some tactical patterns like Action corresponding to Domain Driven Design. Also use Model View Presenter and Factory.
I didn't have more time to implement a corresponding difficulty progression but you can find them in the ScriptableObjects To further improve, I would take the coupling between the game matrix and the game controller itself.
I hope you like it!
