In Drupal 8 theming and templating are quite different than in Drupal 7. But D8 is providing very seamless options and lots of addons to make theming easy.
One of the power tool which helps to debugging and theming is Kint. Kint is a powerful and modern PHP debugging tool. Kint wisely detects what kind of data is being displayed and provides nicely formated data.
Twig is a flexible template engine for PHP. In Drupal Twig is using as default template engine. Twig is flexible, fast, and secure. Here we are going to discuss how we can integrate twig in Drupal 8. We will go through how to use twig template and how we can add new template for a block.
It has been three years since Drupal 8 is released. Even Drupal community has providing seamless support through forum and other resources(eg: IRC) still people are struggling during D8 development. So I'm sharing my D8 development experience here.
Majority will agree that most difficult part in Drupal development is theming. As Drupal is rendering html with its own containers and attributes achieving the exact design provided by UI developers in Drupal feels like a challenge to the developers.