This chapter introduced you to the world of OOP. You saw how to send messages between objects. You learned how to combine objects together to form more complex objects. You were introduced to inheritance, the process of creating new classes based on existing ones. You saw how to extend a derived class by adding new methods. You also saw how to override inherited methods. You learned how to write and import your own modules. You were shown an example of how to sketch out your classes before you begin a project. And finally, you saw all of these concepts come together in the creation of a multiplayer, casino-style card game.