Summary
Drupal provides theming as a means of controlling the visual display of a Drupal application. Themes exist for both frontend and administrative visuals and adding them is a non-trivial development task. This chapter covered the major aspects of a theme in CSS, JS, Twig templates, and the expected Drupal directories and configuration. Best practices were covered for development, debugging, and so on. Emerging concepts such as single-file directories and community-related contributions also can help address specific use cases.
The next chapter covers Drupal’s features tied to web service APIs that enable decoupled and headless application use cases.
