.box_yf ul{
    margin: -4px -2px 0;
}
.box_yf .con{
    display: block;
    overflow: hidden;
    position: relative;
    height: 0;
    padding: 0 0 130%;
    margin: 4px 2px 0;
}
.box_yf .con img{
    width: 100%;
}
.box_yf .con .tit{
    position: absolute;
    bottom: 20px;
    width: 100%;
    text-align: center;
    font-size: 24px;
    color: #fff;
}

@media screen and (max-width: 768px){
    .ul4 li {
        width: 50%;
        float: left;
    }
    .box_yf .con .tit{
        font-size: 18px;
        bottom: 12px;
    }
}