This is Tic-Tac-Toe programmed in x86 Assembly so that it can run without the operating system. It is also possible to run it under DOS. The DOS program version is smaller because it can delegate some responsibility, but even the program that runs by itself is only 512 bytes!
The game include perfect AI with some variation so that it doesn't always make the same response to a series of moves (though it will never lose).
386 or Compatible
64 KB RAM
CGA Graphics Adapter or Compatible