中级 难度星级:☆☆★★★
知识点:交叉用9根火柴,怎样摆放,才能摆出6个正方形? yyQ1dgrk5X3oO7TsG5AmgL8fHYT1unqVsAnIw1O2rLNDB31AmGZVKjsJyIZkR4rw