If you haven't memorized everything, or if some of the code seemed a bit too in-depth, then you have still succeeded.
If you just understand that OOP is about writing reusable, extendable, and efficient code through encapsulation, inheritance, and polymorphism, then you have the potential to be a Kotlin master.
Simply put, OOP enables us to use other people's code, even when those other people were not aware of exactly what we would be doing at the time they did the work.
All you have to do is keep practicing, because we will constantly be using these same concepts over and over again throughout the book, so you do not need to have even begun to master them at this point.
In the next chapter, we will be revisiting some concepts from this one, as well as looking at some new aspects of OOP and how it enables our Kotlin code to interact with our XML layouts.