.case {
    width: 79%;
    margin: 0 auto;
    padding-bottom: 20px;
}

.banner {
    width: 100%;
    margin-bottom: 20px;
}
 .banner img {
    width: 100%;
    height: 100%;
}
.case .case_nav {
    width: 100%;
    display: flex;
    justify-content: center;
}
.case .case_nav .nav_item {
    text-align: center;
    box-sizing: border-box;
    cursor: pointer;
    padding:  8px;
    margin-right: 3%;
    color: #999;
    font-size: 18px;
}
.case .case_nav .nav_item:hover {
    color: #E77917;
    border-bottom: 2px solid #E77917;
}
.case .case_nav .active {
    color: #E77917;
    border-bottom: 2px solid #E77917;
}
.case .case_content {
    padding-top: 35px;
    width: 100%;
    display: flex;
    flex-wrap: wrap;
    border-bottom: 2px solid #ccc;
}
.case .case_content .case_item {
    position: relative;
    text-align: center;
    width: 31%;
    margin-right: 3.5%;
    margin-bottom: 40px;
}
.case .case_content .case_item:nth-child(3n) {
    margin-right: 0;
}


.case .case_content .case_item .title {
    box-sizing: border-box;
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 30px;
    line-height: 30px;
    text-align: left;
    padding-left: 15px;
    display: none;
    color: #fff;
    background: rgba(0, 0, 0, .4);
}
.case .case_content .case_item a img {
    width: 100%;

    transition: all .5s;
}
.case .case_content .case_item  .mask {
    overflow: hidden;
    color: #fff;
    position: absolute;
    text-align: center;
    opacity: 0;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%; 
    z-index: 2;
    background: rgba(0, 0, 0, .4);
    transition: all .5s;
}
/* .case .case_content .case_item  .mask:hover {
    opacity: 1;
} */
.case .case_content .case_item  .mask h1 {
    text-align: left;
    width: 85%;
    margin: 10% auto 5%;
    font-size: 22px;
}
.case .case_content .case_item  .mask p {
    width: 85%;
    margin: 0 auto;
    text-align: left;
    display: -webkit-box;
    overflow: hidden;
    -webkit-box-orient: vertical;
    -webkit-line-clamp: 4;
}
.case .case_content .case_item  .mask img {
    margin-top: 20px;
    width: 30px;
    height: 30px;
}
.case .case_floor {
    display: flex;
    justify-content: center;
    padding: 40px 0;
    width: 100%;
}
@media screen and (max-width: 1600px) {
    .case {
        width: 90%;
    }

}
@media screen and (max-width: 1400px) {
  .case .case_content .case_item  .mask h1 {
    margin: 5% auto;

}

}



@media screen and (max-width: 1280px) {
    .banner  {
        height: 35vh;
    }
    .case .case_content .case_item  .mask img {
        margin-top: 10px;
    }
    .case .case_nav .nav_item {
        font-size: 16px;
    }
    .case {
        width: 95%;
    }
    .case .case_content .case_item .mask p {
        overflow: hidden;
        display: -webkit-box;
        -webkit-line-clamp: 4;
        -webkit-box-orient: vertical;
    }
    .case .case_content .case_item  .mask h1 {
        text-align: left;
        width: 85%;
        margin: 5% auto ;
        font-size: 16px;
    }


}
@media screen and (max-width: 1024px) {
    .case .case_content .case_item  .mask h1 {
        text-align: left;
        width: 85%;
        margin: 5% auto 2%;
         }
    header nav .search>img {
        top: 24%;
        right: -5px;
        width: 15px;
        height: 15px;
    }
    header nav .search {
        top: 17px;
    }
    .case .case_content .case_item  .mask p {
        -webkit-line-clamp: 3;
    }

}
@media screen and (max-width: 860px) {
    .case .case_content .case_item {
        width: 49%;
        margin-bottom: 10px;
    }
    /* .case .case_content .case_item:nth-child(3n) {
        margin-right: 2%;
    } */
    .case .case_content .case_item {
        margin-right: 2%;
    }
    .case .case_content .case_item:nth-child(3n) {
        margin-right: 2%;
    }
    .case .case_content .case_item:nth-child(2n) {
        margin-right: 0;
    }


}
@media screen and (max-width: 800px) {
    .case .case_nav .nav_item {
        font-size: 12px;
    }
    header nav .search>img {
        top: 28%;
    }
    .m-style a {
        width: 30px;
        height: 30px;
        line-height: 30px;
    }
}


@media screen and (max-width: 750px) {
    .banner {
        height: 20vh;
    }
    .case .case_content .case_item .title {
        display: block;
    }
     .case .case_content {
        padding-left: 0px;
        
    }
    .case .case_nav .nav_item {
        padding: 5px;
    }
    .case .case_content .case_item  .mask h1 {
        text-align: left;
        width: 85%;
        margin: 10% auto 2%;
        font-size: 18px;
    }
    /* .case .case_content .case_item  .mask h1 {
        display: none;
    }
    .case .case_content .case_item  .mask p {
        display: none;
    } */
}
@media screen and (max-width: 500px) {


    .m-style a {
        width: 20px;
        height: 20px;
        line-height: 20px;
    }
    .m-style .active {
        width: 25px;
        height: 25px;
        line-height: 25px;
    }
    .m-style span {
        width: 25px;
        height: 25px;
        line-height: 25px;
    }
    .case .case_content .case_item .mask h1 {
        margin: 4% auto;
        font-size: 14px;
    }

}
@media screen and (max-width: 375px) {
    .banner img {
       height: 160px;
    }
    .case .case_nav .nav_item {
        padding: 0px;
    }
    .case .case_floor {
        padding: 15px 0;
    }
    .case {
        padding-bottom: 0;
    }
    /* .case .case_content .case_item .mask p {
        overflow: hidden;
        display: -webkit-box;
        -webkit-line-clamp: 3;
        -webkit-box-orient: vertical;
    } */

}