[maxloh]

Maybe add `flex: 1` to the second column?

[eternityforest]

The second column can't always just be a tall column shaped div, because you probably want to reflow 12, 34, 56, 78 on mobile where you don't have room for 2 columns, to something like 12345678, not 13572468

[maxloh]

You can reorder flex children with the CSS `order` property.

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