5.30

flex

修改主轴方向 flex-direction

主轴和侧轴仅仅只是方向调换

row

弹性盒子换行 flex-wrap

flex-wrap:wrap;

调整侧轴对齐方式 align-content

设置align-contene前提条件是：必须要先设置flex-wrap:wrap；

align-content:flex-start;

align-content:flex-end;

align-content:center;

align-content:space-around;

align-content:space-between;

align-content:space-evenly;