display:flex;/*flex块级,inline-flex:行内快*/
justify-content:space-around;/*center:水平居中,flex-start:靠左;flex-end:靠右;space-between:两边的向两边靠,中间等分;space-around:完美的平均分配*/
align-items:stretch;/*center:垂直居中、flex-start:至顶、flex-end:至底、space-between、space-around*/
flex-direction: row;/*column从上向下的排列,column-reverse、row:从左到右,row-reverse:从右向左*/
flex-wrap:wrap;/*wrap多行显示(父容器不够显示的时候,从上到下)、nowrap(当容器不够宽的时候,子元素会平分父容器的宽或者高)、wrap-reverse:从下向上*/
/*flex-flow是flex-direction、flex-wrap的缩写*/
补:常用的组合是 : flex-direction: column;justify-content: space-between;
补:应用justify-content:center;justify-content:space-bettween时通常与padding:0 20px来使页面美观