[ImHereToVote]

If you are gonna use shaders. Why not create the whole boxes as meshes? Why bother with the CSS at all?

[ZachSaucier]

The author creates art using their own custom library that uses CSS-like syntax to render HTML, SVG, and more recently shaders. The point isn't that this is the best way to do it. It's simply a trick that the author used to do something with their own bespoke library that they were trying to do.