.header-bottom {
    height: 4.3rem;
}

.header header {
    background-color: rgba(21, 53, 178, .9);
}

.banner {
    position: relative;
    width: 100%;
    height: 31.25rem;
    padding-top: 11.25rem;
    text-align: center;
    background: url('http://static.web3di.com/img/6_pic1@2x.png') no-repeat center;
    background-size: 100% 100%;
    color: #ffffff;
}

.banner h4 {
    font-size: 3.125rem;
    color: #ffffff;
}
.all-content{
    display: flex;
    width:88.75rem;
    margin:0 auto;
}
.all-content .content-left{
    width:68.75rem;
}
.problem {
    padding: 2.5rem 0;
    background: #f9f9f9;
} 
.problem-title h4{
    text-align: center;
    font-size: 2.1875rem;
    color: #000000;
    margin-bottom: 3.75rem;
}
.problem-content {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    background:rgba(255,255,255,1)
}
.problem-item{
    width: 31.25rem;
    height: 4rem;
    line-height: 4rem;
    border-bottom:1px solid rgba(232,232,232,1);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.problem-item a {
    font-size: 1rem;
    color: #666666;
}
.problem-item span {
    display: none;
}
.recommend-content{
    margin-top:2rem;
}
@media screen and (max-width: 750px) {
    .banner {
        width: 46.875rem;
        height: 15rem;
        padding-top: 4.25rem;
    }
   
    .banner h4 {
        margin-bottom: 2.25rem;
    }
    .problem-content {
        width: 41.875rem;
    }
    .problem {
        padding:2.875rem 0;
    } 
    .problem-title {
        margin-bottom: 2.125rem;
    }
    .problem-item span {
        display: inline-block;
    }
    .problem-item{
        width:100%;
    }
}