I've been building for the fast/embeddable browser engine niche:

Source: https://github.com/dioxuslabs/blitz

Status: https://blitz.is/status/css

Typical binary sizes are around 10-20mb, although you can go smaller by doing things like excluding features or compiling with `Os`/`Oz`.

There's no JavaScript yet (which can also be a benefit of course!), but people have recently started experimenting, and we may well start on this soon.