gap is flow relative, meaning it changes dynamically based on the direction of content flow. For example, gap will automatically adjust for the different writing-mode or direction values that you set for your international users. This significantly eases the burden of spacing challenges for the component and CSS author. Less code scaling further.
Gap demonstrating localization support, as it handles changes to direction and writing-mode: Codepen | Tweet
Before gap was in Flexbox, strategies involved negative margins, complex selectors, :last or :first type pseudo-class selectors, or other means to manage the space of a dynamically layed-out and wrapping set of children.
The above are not a full replacement for gap though, and often need @media or :lang() adjustments to account for wrapping scenarios, writing modes or direction. Adding one or two media queries doesn't seem so bad, but they can add up and lead to complicated layout logic.
What the above author really intended was to have none of the child items touch.
In the first 2 examples (without Flexbox gap), the children are targeted and assigned spacing from other elements. In the antidote gap example, the container owns the spacing. Each child can relieve itself of the burden, while also centralizing the spacing ownership. Simplifying consistency. Reorder, change viewports, remove elements, append new elements, etc. and spacing remains consistent. No new selectors, no new media queries, just space.
With Flexbox gap, we unlock more than convenience. We unlock powerful, perfectly spaced, intrinsic layouts. In the video and following code sample below, Grid cannot achieve the layout that Flexbox can. Grid must have equal rows and columns, even if they're intrinsically assigned.
Also, notice how dynamic the spacing between children is when they wrap intrinsically like that. Media queries can't detect wrapping like that to make intelligent adjustments. Flexbox gap can, and will, do it for you across all internationalizations.
