Comment by cr0sh

For future explorers:

I found this:

https://winworldpc.com/product/sunos/4x

Download the file "SunOS 4.1.4 Solaris 1.1.2 Source" - go to the "demos" directory and a bit of searching you can find the "suncube.c" file.

Lots of dependencies on "suncore" graphics libs and such, but the code is there. Also - check out the /games folder - it has C source in it for "adventure", "hack" (nethack), and "trek" (star trek).