Introduction - If you have any usage issues, please Google them yourself
/* in the begin,there is only a snake head,and it will have to eat food*/
/* to become stronger,and it eat a piece of food each time,it will*/
/* lengthen it s body,with the number of food the snake eats going up,it*/
/* will become long more and more,and the score will goes up also.*/
/* there is always useful information during the game process.*/
/* if the path by which the snake goes to eat food is the shortest,the*/
/* score will add up a double.