For getter properties in Gosu, what should they not do?

Getter properties in Gosu are designed to retrieve a value associated with an object without causing any side effects or modifying the object's state. The key principle behind a getter is that it retrieves data in a way that is predictable and does not change any aspect of the system's state.

When a getter alters data, it can lead to unexpected behavior and makes the property less intuitive for users of the class, who typically expect getters to simply return values. By avoiding any alterations to data within a getter, you maintain the integrity and simplicity of your code, allowing for easier maintenance and a clearer understanding of how the properties interact within the program.

The other options relate to practices that are acceptable for getter properties: they can return computed values, they do not require parameters, and they can be declared as final, depending on the specific design considerations within the class. Each of these aspects contributes to flexibility in implementation but does not compromise the purpose and expected behavior of a getter property in Gosu.