IconVault's CSS reading-flow lab teaches the property that fixes one of the sneakiest accessibility bugs in modern CSS. Reorder cards with flex-direction: row-reverse, column-reverse or the order property, then step through the simulated keyboard walk: with reading-flow: normal focus follows DOM order while your eyes see something else; with flex-visual or flex-flow the Tab path matches the visual layout.

The tool is free and runs fully in your browser. Because reading-flow is still experimental and not in stable browsers, the focus walk simulates the spec algorithm and says so plainly, while the copied snippet applies the real property so your CSS is ready when browsers ship it. You will leave knowing exactly when to reorder the DOM instead.