This week, we've added 8 new tutorials to our Drupal 8 Theming Guide on breakpoints, responsive image styles, and core themes Bartik and Stark. In these lessons you will learn about breakpoints and media queries, and how Drupal uses these concepts outside of CSS files. We'll cover breakpoint configuration files and how to create one for your theme or module. Then, we'll dive into the Responsive Image module. We'll explore responsive image style configuration, popular responsive image use cases that you can solve with responsive image styles, and, step-by-step, how to create a responsive image style for a viewport-sizing use case. Finally, we have a pair of tutorials on Bartik and Stark. We'll take a look at these core themes, their purpose, and what you can learn from them.