In this chapter, we created a sub-theme derived from the Bluemarine template included with Drupal 6. After an overview of the theme architecture, we created the Descartes theme. Initially, we made changes using only CSS. Then we added a custom PHPTemplate. To add a little additional functionality, we implemented the theme_breadcrumb() function in our template.php file. And we wrapped up our theme by adding a screenshot. Finally, we took a look at the steps necessary for moving from a sub-theme on to an independent theme.

But this chapter isn't the last time we will hear about themes. As we continue creating new modules, we will make use of our newly-gained theme knowledge to provide default theming for new content and to interact with the theme system from within a module.