你玩过“拉灯”游戏吗？25盏灯排成一个5x5的方形。每一个灯都有一个开关，游戏者可以改变它的状态。每一步，游戏者可以改变某一个灯的状态。游戏者改变一个灯的状态会产生连锁反应：和这个灯上下左右相邻的灯也要相应地改变其状态。-You played " pull light"　games? 25 lights arranged in a 5x5 square. Each lamp has a switch, the game can change its state. Each step, players can change the status of a lamp. Game to change the status of a lamp will have a ripple effect: and the lamp lights up and down about adjacent to a corresponding change in their status.