VIP26/day22/css/9.demo.css

.container {
    display: flex;
    height: 220px;
    overflow-x: scroll;
    /* overflow-y: scroll; */
}
.main {
    flex: 1;
    display: flex;
}
#box {
    width: 200px;
    height: 200px;
    background: #f00;
    margin-left: 20px;
}