Drupal core comes with a few base themes: Stable, Stable 9, Classy, and Stark. Each one has a different intended use case. And all of them are useful as a reference for building your own themes.

In this tutorial we'll:

• Learn what each of the base themes included in Drupal core is intended to be used for
• Compare the output from the base themes with a focus on Stable and Classy

By the end of this tutorial you'll be able to explain the use case for each of the base themes included with Drupal core and make an informed decision about which, if any, to use when creating your own custom themes.

It's time to create the bare-bones structure for a new theme on your site. You should try to complete this exercise based what you've learned from the tutorial prerequisites listed below. In this exercise, we'll:

• Create an info file that describes a custom theme to Drupal with the regions listed below (we're going to name ours "reboot").
• Enable, and view, a bare-bones custom theme.

By the end of this exercise, you should feel comfortable starting a theme using several methods.

The available dynamic tokens or variables vary from template to template. Each page is built from a set of templates.

In this exercise, we'll:

• Override and name the node template file so that it will only affect Article nodes on our Drupal site.
• Inspect the available variables.
• Customize the markup.
• Use the Twig filter without.

We recommend that you try to work through the exercise yourself, and refer to the video if you need help.

Themes define the regions that are available for site administrators to place blocks in, creating a layout framework within which the components that compose a page can be placed. As a theme developer you'll need to determine what regions are necessary to accommodate your design's layout, while also ensuring it'll work with the way Drupal uses blocks to place content onto the page. Deciding what regions to create requires knowledge of how Drupal works and a clear vision of the design you're trying to achieve.

In this tutorial we'll:

• Explain what regions are and how they relate to themes
• Describe how regions are handled internally within Drupal
• Demonstrate things to keep in mind when planning the regions for your custom theme

By the end of this tutorial you should be able to describe what a region is, explain how Drupal themes use regions to place content, and get started dissecting your own designs into regions.

Stark is one of the themes bundled with Drupal. It is intentionally bare bones and its purpose is to help Drupal theme and module developers get to the heart of Drupal's system templates. In this tutorial, we'll explore Stark and its primary features and discuss the various reasons for utilizing the Stark theme.

Some, but not all, themes come with administrator-configurable settings that you can change through the UI. These might allow you to upload your own logo, choose between a couple of different pre-defined layouts, or turn features of a theme on or off. In this tutorial we’ll look at where you can find these theme settings if they exist, and how to go about changing them.

To add CSS or JavaScript files or libraries to your site, you can attach them as asset libraries in your theme. In this exercise, you'll create 2 asset libraries and attach them globally via your theme's info file. In this tutorial, we'll pull in the CSS and JavaScript from the popular Bootstrap framework so that we can make use of its layout utility classes later on. We'll also add a custom CSS file that contains global styles for our site, like setting the page background color.

If you want to try and complete this on your own first you'll need to:

• Add the Bootstrap CSS and JavaScript files to your theme.
• Define an asset library using a THEMENAME.libraries.yml file in your theme.
• Tell Drupal to attach your asset library so that the CSS and JavaScript files it represents are included in the page.

Once that's done your site won't look all that different. But if you view the page source, or look closely, you should see that the Bootstrap files are included along with any CSS rules you placed into your custom style sheet.

Note: Since this course is focused on teaching the Drupal aspects of theme development, and not on writing CSS, we're using the Bootstrap CSS. Feel free to use the framework or library of your choice if you don't want to use Bootstrap.

You should try to complete the exercise steps on your own and use the video to help guide you if you get stuck.

At the end of this exercise, you'll find a video walk-through of the solution.

In order to change Drupal's default markup you need to override template files. The page template controls the overall layout of your theme, including the placement of regions. You should practice the exercise following the written instructions below. Use the video walk-through to help if you get stuck.

In this exercise, we'll:

• Override the currently used page.html.twig template file.
• Modify the content of the file to include the regions defined in the theme's .info.yml file.
• Wrap the regions in the page template file with HTML markup using CSS classes from Bootstrap to achieve the example layout.

By the end of this tutorial, you'll gain practice creating a custom layout in a page template file.

Knowing how to clear Drupal's cache is an important skill for any developer. You'll likely find yourself doing it frequently in order to get Drupal to register the changes you make to your code, or other updates you make via the UI. It is also a good first step to trouble shooting problems with your Drupal site: Clear the cache before you do any other debugging to ensure it's not just a bad cache entry.

Drupal comes with all of its caching features enabled by default. This improves response time, but can be frustrating for themers as it makes it harder to preview the changes you make to template files.

In this tutorial we'll look at:

• Why these features are enabled by default
• How the theme layer leverages Drupal's caches
• Why you should learn to disable them when doing development