Not apparent at first, but this is a TypeScript to c++ compiler at the core (https://github.com/geastack/compiler), with bindings for various platforms.
Each platform has its native bindings. For graphics, you write CSS and HTML canvas API as well as JSX, it renders to native components and their alignments, the canvas API is converted to native surfaces, whatever the platform uses.
In the docs of the repo of their TS to C++ compiler. https://github.com/geastack/compiler