[tompazourek]

> In terms of what you can't do with plain old inline CSS?

AFAIK you cannot do responsive stuff (media queries) in the style attribute.

[Semiapies]

I don't see than you can really work with arbitrary media queries in this, either. There are just some combinations of widths and orientations baked in, which is nothing new.

[tompazourek]

You're right that you still cannot do arbitrary media queries there. But from my experience (I'm not a designer though), staying within a set of predefined breakpoints (xs, sm, md, lg, xl) is often enough for most web pages.

The style attribute doesn't allow you to do anything responsive at all on the other hand.

[Semiapies]

That's what classes are for. (Which this also reinvents.)