I often set gaps between elements to 1rem or more. Coloring the gap wouldn’t be the same as adding a rule.

My “theory of layout” is that no element should have any styling that relates to its relationship with other elements. Gap is very useful for establishing spacing.

Perhaps with margin: auto your :gap element can sit in the middle of the “gap space”?

I think we’re getting into kludge territory there. Might as well have an explicit property that can be autocompleted/stumbled upon via spec or docs than an implicit behavior born of a little trick.

Knowing how CSS tries to support direction agnostic layouts the pseudo elements would be:

:gap ( -[inline\block] ( -[start/end] ) )

You know how the shorthands work elsewhere, so this just replicates that.

Isn't it (technically, officially) two colons for a pseudo-element? ::gap instead of :gap.

I believe that was deprecated for reasons I don't understand, but admittedly, I'm too lazy to check since I'm on my phone.

I think a `gap-image`, similar to `border-image` would be more flexible.

Came here to make the exact same comment, just being able to specify a border feels a little shortsighted.

Came here to say this too, the flexibility of having something like :after would mean not having to consider all the potential ways people are going to want to use this.

Not sure about content: though, that could get weird.