Using CSS, we can make nested ordered lists automatically display in a numbered hierarchy—like "1, 1.1, 1.2, 2, 2.1", without any additional HTML markup changes. Here’s how to set it up!
Single-Directory Components (SDC) is the biggest change to Drupal theming since the introduction of Twig. Here's an "unboxxing" walkthrough of how it works.
Drupal currently supports IE11, and will do until Drupal 10 in about a year's time. Here's my proposal for how to support IE11 in a distribution without holding back from modern CSS.
We often end up with a lot of templates when theming, but we should also remember to create "sensible defaults", so before you start theming specifically your site doesn't look broken.