The original Rival Chess for MS-DOS C++ Source Code.
There was a time when you had to write your own mouse handling routines and draw your own mouse pointer on the screen. And erase it again. And draw it again. Etc.
This was written between 1988 and 1990 as a way to teach myself C by converting an old Pascal chess program I had written a few years earlier.
It then evolved into a C++ project, developed using the superb Turbo C++ IDE.
It has a mouse-driven DOS GUI. The graphics were created by Russell Newman.