/*样式*/
.m-bg {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-repeat: no-repeat;
    background-position: center center;
    -webkit-background-size: cover;
    background-size: cover;
    -webkit-transition: all .5s;
    -o-transition: all .5s;
    transition: all .5s;
    -webkit-transform: translate3d(0,0,0);
    transform: translate3d(0,0,0);}

.pic2 {
    padding-top: 70%;
    position: relative;
    overflow: hidden;}