printScreen：刷新屏幕输出的图像。

Start：用户进入程序时选择开始，退出和求助。

Leave：用户离开程序事提示感谢使用

levelChoice：用户开始之前选择等级

newWord：生成一个新的字母并将其置于首行。

moving：将屏幕上的所有字母向下移动一行

wordHit：判断用户是否输入字母，如果输入，且屏幕上有该字母则将该字母所在位置置空。

result：判断该用户的得分，提示其是否进入下一等级。

main：总体控制以上各函数，判断其是否运行。

-PrintScreen: refreshes the screen output images.

Start: users to program choice to begin, exit and ask for help.

Leave: users Leave things tip thank use program

LevelChoice: before the start of the user choice level

NewWord: create a new letters and placed it in the first line.

Moving: will all the letters on the screen move down the line

WordHit: judge whether the user is input letters, if the input, and the screen this letter will this letter for the position of the empty.

Result: whether the user s score, tip if it into the next level.

Main: overall control of these functions, to judge whether the operation.