We had no need for the Player class since this recipe uses the built-in runtime class called PlayerPrefs, which is provided by Unity.
Unity's PlayerPrefs runtime class is capable of storing and accessing information (the string, int, and float variables) in the user's machine. Values are stored in a plist file (Mac) or the registry (Windows), in a similar way to web browser cookies, which means they are remembered between game application sessions.
Values for the total correct and incorrect scores are stored by the Start() methods in the IncrementCorrectScore and IncrementIncorrectScore classes. These methods use the PlayerPrefs.GetInt("") method to retrieve the old total, add 1 to it, and then store the incremented total using the PlayerPrefs.SetInt("") method.
These correct and incorrect totals are then read each time the scene0_mainMenu scene is loaded, and the score...