The document describes the rules of Tic-Tac-Toe (OOXX) game. It is a 3x3 grid game where two players take turns marking spaces with "O" or "X" symbols. The first player to mark 3 of their symbols in a row (horizontal, vertical or diagonal) wins. If all 9 spaces are filled without a winner, the game ends in a draw. The document then provides code for a C# OOXX game program that implements these rules.