.topic-bg img{display: block;overflow: hidden}
.topic-form{width:100%;height: 0;padding-bottom: 312.5%;position: relative;background-image: url('3.jpg');background-repeat: no-repeat;background-size: cover}
.topic-form input{width:58%;height:3%;left:21%;border:0;position: absolute;font-size: 0.28rem;display: flex;justify-content: center;align-items: center;outline: none}
.topic-form input:nth-child(1){top:75.25%}
.topic-form input:nth-child(2){top:80.85%}
.topic-form input:nth-child(3){top:86.3%}
.topic-form a{display: block;position: absolute;width:60%;height:4%;top:91.15%;left:20%}