 Custom properties are a new addition to CSS. They're better known under a different name, CSS Variables. In the past, web developers have used preprocessors like Sass, Les or Stylist to have this functionality. The advantage of using the standardized custom properties is that you can change their values during runtime using media queries, JavaScript or dev tools and immediately see the effect of your changes. With this in place, it makes sense to make a lot of your values dependent on custom properties. In this example, the size of the ribbon as well as the ribbon flap have been defined using custom properties and are used in many calc expressions to position and size other elements. I can change these properties in dev tools to find the ideal value for my layout. It's especially useful to define a padding variable that is used as a base unit whenever you're defining a gutter, margin or padding. This way, you have a single lever to make a design feel more or less spacious. More patterns will probably evolve in the new future around custom properties as they become best practice, but even now, they are widely supported and allow you to make rapid changes and keep your design much more flexible. Good stuff, innit? See you next time. I mean, we all know that Supercharged is clearly the best, but we do other series as well, which you should totally watch and for that reason, you should subscribe to this YouTube channel. And if you want to see the most recent Supercharged live stream, you can click it over there.