So, digging through the website git repo a bit, some basic facts:

* The project started almost 11 years ago, in 2015.

* It can be both a build-system generator like CMake, or a 'builder' like Make or ninja.

* Code is almost exclusively by one person, waruqi: https://github.com/waruqi , with several other people making a few contribution.

* Prima facie, the API seems to be less flexible/rich than CMake's, but I'm not sure.

* It supports quite a few languages, despite saying "C/C++" on the website.

* It has a built-in REPL.

As @MobiusHorizons points out, a comparison with other build system generators would be appropriate, mostly CMake, but I did not find it.