父：
display: flex;
flex-direction: row/column;
flex-wrap: nowrap/wrap; 是否换行
flex-flow: direction wrap; 简写

justify-content:
flex-start/flex-end/center/space-between/space-around 水平
align-items:
flex-start/flex-end/center/baseline/stretch 垂直
align-content:
flex-start/flex-end/center/baseline/stretch 每行的个性化，一行时无效

子:
align-self:
auto/flex-start/flex-end/center/baseline/stretch 相对父，在垂直方向个性化
flex-grow: 拉伸 不接受负值 0
flex-shrink: 收缩 不接受负值 1
flex-basis: 伸缩的基准值 不接受负值
flex: grow shrink basis 简写