Interesting, they flipped the problem around.

The UI toolkits in game engine usually suck hard, so here they started from a good UI toolkit and made it possible to make relatively performant games.

There's more info at https://www.reddit.com/r/programming/comments/1r0lx9g/fluori...

Qt Quick 3D in Qt is I guess a similar value prop.

They have a fun demo of a 3D shooter in it.