Drupal themes can be as simple or as complex as you need them to be. Themes have the final say and ultimate control over almost every aspect of each page. Like Drupal itself, themes are flexible and powerful. Admittedly, taking full advantage of Drupal's theme layer means overcoming a rather steep learning curve, and without a general understanding of what's going on under the hood, it is easy to make mistakes early on.
In this chapter, you will learn about the basic aspects of Drupal's theme layer. You'll learn how to go about making customizations and changes in a sustainable way and best practices for common tasks. You will be well on your way to creating flexible and sustainable custom Drupal themes in no time! The next chapter will build on this one and will cover the more advanced intricacies of Drupal themes.
Some of the examples you'll find throughout this chapter and the next can be found in the DGD7 theme. It's available at https://github.com/jacine/dgd7 for download if you'd like to follow along.