Author here - it's just 20 videos broken apart into each topic so when you need to come back to reference something, it's quick.

Is flexbox hard to learn? Yes, but it's because it's such a powerful layout tool. There are tons of gripes about Flexbox, but I've found that if you just put in a few hours to learn it, you are going to be way ahead in your CSS and layout game.

We haven't had to learn anything hard in CSS for years and now it's time. Hunker down and get at it!