相关属性flex-direction:column1.justify-content:flex-start (紧贴红线顶部)2. justify-content: center (在红线上垂直居中)3. justify-content: flex-end(在红线上垂直居中)4. justify-content: space-between (沿红线均匀撑开)5. justify-content: space-around (沿红线均匀分布)1. flex-wrap: wrap (装不下就换行)对比flex-wrap: nowrap (默认死活不换行)2. flex-grow: 1 (平分剩余空间)对比flex-grow 比例分配 (1:2:3)3. flex-shrink 演示 (空间不够时的退让)对比第三个盒子拒绝收缩 (flex-shrink: 0)flex-direction:row交叉轴方向