> don’t rely heavily on a superset of JS or CSS and instead focus heavily on web standards that work across browsers and platforms Worth keeping in mind that t

> don’t rely heavily on a superset of JS or CSS and instead focus heavily on web standards that work across browsers and platforms Worth keeping in mind that this is not really the dichotomy. The supersets of JS and CSS do work across browsers and platforms, because they are compiled down to JS and CSS. If you're just wondering what to do to learn responsive design, first step would just be to read docs for the @media query [1]. Also, learn flexbox. Maybe you will want to learn some of the other new CSS constructs (grid, columns) if you don't care too much about backwards compatibility. If you've done all that and still want to learn more, next step would probably be to deconstruct an existing library like Bootstrap or something that targets the platforms you want to. [1] https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Using_media_queries https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queri...