3.align-items

1.align-itmes:flex-start 则从上到下；

.box{
                width: 200px;
                height: 200px;
                border: 1px solid red;
                margin: 100px auto;
                display: flex;
                flex-direction:row;
                justify-content:space-between;
                align-items:flex-start;                
            }
            .box span{
                display: inline-block;
                width: 30px;
                height: 30px;
                background-color: pink;
                border-radius: 50%;
            }

2.align-itmes:flex-end 从下到上

.box{
                width: 200px;
                height: 200px;
                border: 1px solid red;
                margin: 100px auto;
                display: flex;
                flex-direction:row;
                justify-content:space-between;
                align-items:flex-end;                
            }
            .box span{
                display: inline-block;
                width: 30px;
                height: 30px;
                background-color: pink;
                border-radius: 50%;
            }

3.align-itmes:center 垂直居中

.box{
                width: 200px;
                height: 200px;
                border: 1px solid red;
                margin: 100px auto;
                display: flex;
                flex-direction:row;
                justify-content:space-between;
                align-items:center;                
            }
            .box span{
                display: inline-block;
                width: 30px;
                height: 30px;
                background-color: pink;
                border-radius: 50%;
            }

4.align-items:stretch 拉伸 (不设置高)

.box{
                width: 200px;
                height: 200px;
                border: 1px solid red;
                margin: 100px auto;
                display: flex;
                flex-direction:row;
                justify-content:space-between;
                align-items:stretch;                
            }
            .box span{
                display: inline-block;
                background-color: pink;
            }