说明：  产生一个固定大小没有边界的游戏区域，蛇从区域的中心开始，由玩家通过键盘控制蛇的运动方向，用蛇头去吃随机分布在游戏区域内的食物； 蛇的运动限制在游戏区域内，游戏区域没有边界，所以蛇在区域内作循环运动； 蛇的运动方向为直线运动，只走横和竖的方向，不走斜线； 蛇的运动速度由游戏的难度来控制，难度越高，速度越快，游戏难度分为9个等级； 蛇身体的长度从1开始每吃掉一份食物就增加一个长度； 食物的出现安照随机分布的原则，蛇吃掉一份后随即在游戏区域内放一份新的食物； 每吃掉一份食物得分为10*游戏的难度，游戏结束后统计全部的得分； 游戏结束的条件为：在控制蛇的过程中蛇头碰到蛇的身体的任何部位
(Generating a fixed size no boundary game region, snakes from the beginning of the center of the region, by the players on the direction of movement of the keyboard control snake with snakeheads eat food randomly distributed within the game region restrict the movement of the snake in the area of ​ ​ the game, the game region no boundary in the region, so the snake for circulating motion the direction of the movement of the snake into linear motion only go in the direction of the horizontal and vertical, do not take a slash snake speed of movement is controlled by the difficulty of the game, the higher the degree of difficulty, the speed faster the difficulty of the game is divided into nine grades snake body length from 1 to start each eat a food on an additional length the food appear Yasuteru random distribution principle, immediately after the snake eats a play area conditions of the end of the game: snakeheads encounter snakes snake control any part of the body to pu)