XenevaOS: a custom operating system with networking and graphical desktop environment

Xeneva is an operating system for both x86_64 and ARM64 architectures, built from the ground up. The Kernel is known as Aurora' with hybrid kernel design and the entire operating system is known as Xeneva'.

XenevaOS GitHub page

It's remarkably complete, with driver loading and linking, up to SSE 3 support, USB3 and Intel HD audio support, networking, and a whole lot more of the basics that make up a modern complete operating system. On top of all this, it also has a compositing window manager, a desktop environment, a terminal with VT100 support, Freetype2 font rendering, and much more. It also comes with a few basic applications like a file manager, calculator, audio player, and so on.

It's written in C (and some C++), and uniquely, can only be built in a Windows environment, something you don't see very often. It definitely looks quite impressive.