In this book, we’ll focus on the customization part - build your own Bootstrap theme. At the time of
writing this book, Bootstrap 4 is still in its alpha version, by “Bootstrap” here we are referring to

Bootstrap 3. We will start with preparing a development workbench, and introducing Less (a CSS pre-
processor Bootstrap uses), then walk through Bootstrap’s source code which will help us first get

familiar with its code structure and later build themes by reusing it. Moreover, we will learn how to
make additional styles and use plugins to polish our themes. Lastly we will touch on Bootstrap 4 a little
and see how to use and customize it.

To learn something new, you need to practice, sometimes a lot. In this book I am following the “learn
by doing” methodology: in most of chapters, I’ll put a “Practice” section. Usually those sections ask
you to go to this book’s code repository (see the next section), open some files and learn the code
inside. Some chapters will also contain a “Challenge” section, which will suggest you to make changes
to the code we learned in that chapter. Those challenges usually are not hard to solve, and there for you
to get your hands dirty, and help you have a better understanding.