Throughout this chapter, you should have gained a basic understanding of object-oriented programming. We have looked at several examples of how to put the encapsulation, polymorphism, abstraction, and inheritance into practice and how they allow us to make scalable applications. The SOLID principles helped us to outline how our classes should be designed. We are now going to put these concepts into use over the next few chapters. We will be developing an interactive drawing application with TypeScript and a little bit of HTML in Chapter 5, Creating a Simple Drawing Application.