The premise is this: You and an opponent represent cats and dogs in a race to claim more territory. You play on a grid. Cats go first, then alternating. Once a cat is set on a grid square, a dog can't be 1 square away from the cat (including diagonals). Whoever claims more territory in the end wins.
My implementation is a bit crude, but it should work on all OSes
Source Code
Compilation: use g++ (Linux/MacOS)/MSYS2 (Windows) for compilation. stdc=17.