盒子产品图不固定产品尺寸正方形布局

.selected_topics a {
position: relative;
display: inline-block;
width: 100%;
height: 0;
padding-bottom: 100%;
vertical-align: top;
overflow: hidden;
}

.selected_topics a img {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
.selected_topics ul {
display: flex;
display: -webkit-flex;
flex-flow: row wrap;
justify-content: space-between;
}