The proposed class hierarchy for different types of "game objects" is exactly the type of hierarchy which will bite you in the ass very soon when adding more features, an entity-component-system would be a better solution for this specific problem (composition instead of inheritance). Newbie programmers should never be taught this "animal - cat - dog" nonsense IMHO because this approach of modelling software after real-world objects doesn't work for anything slightly more complex. For instance, what if you have two different enemy types which both need to implement a common feature but differ in others? Please don't say 'multiple inheritance' ;) This doesn't mean that OOP is bad at all IMHO, just that it shouldn't be treated as a holy grail (applies to all design principles), and doesn't mean that you have to go all-functional. All IMHO of course.