小型的智力游戏（井字游戏）的开发代码。井字游戏又称井字棋、圈圈叉叉等，原本是一个纸笔游戏。这种游戏的变化简单，常成为博弈论和赛局树搜寻的教学例子，同时也是本章选择井字游戏作为开发实例的重要原因之一。可以使读者增强对C#语言的理解，同时对游戏开发的入门学习也起到一定的指导意义。

-Small puzzle game (Tic Tac Toe) development code. Tic-tac-toe game, also known as tic-tac-toe, circle pork on a skewer, which was originally a pen and paper game. Variation of this game is simple, often become a teaching example of game theory and game tree search, but also select the tic-tac-toe game in this chapter as one important reason for the development of examples. Instance learning of this chapter, the reader can make to enhance the understanding of the C# language, started to learn game development at the same time also played a certain significance.