Drupal 8 Theme Development

The Drupal Theme System:
-- Creating new themes
-- Integrating standard Drupal elements (navigation menus, content, blocks)
-- Adding CSS and Javascript libraries
-- Creating and overriding template files
-- Declaring custom theme regions
-- Overriding CSS and Javascript from Drupal core and contributed modules.

The Twig Template Language:
-- Overriding Twig template files
-- Rendering and debugging content variables
-- Formatting content with filters and functions
-- Using conditionals and loops
-- Combining template files together by including and extending

Advanced Drupal Theming:
-- Theming Views
-- Adding custom javascript to themes
-- Using preprocess functions
-- Creating custom templates
-- Implementing responsive designs
-- Using the Responsive Images module