Thanks for your feedback.

Actually Bootstrap v4 provides an opinion to use flex box instead of the traditional grid. http://v4-alpha.getbootstrap.com/getting-started/flexbox/

I would say your suggestion is good. I don't have a convincing reason that `container-side` being a part of the framework. I'll consider to remove it.

What kind of content is never visible on mobile? `Scan the QRCode to view on mobile` and `Go to top` is a kind of this content.

Why does it have to be on the side? I think it's a good design to guide people to view on mobile. Or where do you think it can be?

Thanks!