With some of the videos in the chapter, particularly with those that explain concepts step-by-step by building up a diagram or through animations, a screen is helpful, and in some cases a computer screen rather than a mobile phone will really help too. Other videos are more for listening podcast-style (in the car or on your commute for instance), with visual aids that help, but are not essential.

We'll introduce videos here, but also give hints on where we think the screen is really helpful for understanding, and also say which videos are ok 'just to listen'. Feedback from many was that a listen-only for some lessons would be useful for the car or the commute, so we took that on board.

This is one of those videos you can just listen to.