re `order`: for a usage you probably hadn't considered, that I'm sure you would agree is purely presentational and not application logic, check out:

https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexibl...

tldr:

desktop viewport:

    _header____
    nav|article

mobile viewport:

    header
    article
    nav

can be done really easily with flexbox and `order`.