鼠标选择游戏开始、暂停、重新开始

开始后用键盘控制蛇的运动方向，吃到“食物”并且避免碰到自己的尾巴和边界-Mouse to select the game to start, pause, resume after the start of the keyboard to control the direction of movement of the snake, eat " food"　and to avoid hitting its own tail and boundary