3. Design Principles

The latest Worldwide Developers' Conference at Apple has a link to an hour-long video on 'Essential Design Principles' that does an excellent job of covering these.

I just realised the link requires a developer account at Apple therefore it can't be required viewing for CDG hatchlings, but for those devs with an account, it's great for a review or gentle introduction. more below

The video is available here. https://developer.apple.com/videos/play/wwdc2017/802/