header {
    background-repeat: no-repeat;
    background-size: cover;
    background-image: url("../img/joinIn/banner_1.png");
    color: #fff;
    position: relative;
    height: 500px;
}
.header {
    position: absolute;
    top: 0px;
    left: 0px;
    text-align: center;
    width: 100%;
    height: 100%;
    background-color: rgba(60, 143, 207, 0.4);
}
.page {
    width: 1200px;
    margin-top: 50px;
    margin-bottom: 50px;
    margin: 50px auto;
}
.title {
    font-size: 24px;
    font-weight: bold;
    color: #333333;
    text-align: center;
}
.item-content {
    margin: 50px 0;
    text-align: left;
    font-size: 16px;
    line-height: 40px;
    text-indent: 2rem;
}
.nav-case {
    display: flex;
    justify-content: left;
    font-weight: bold;
    color: #333333;
}
.nav-case > li {
    width: 100px;
    margin: 0 10px;
    padding: 10px;
    text-align: center;
}
.nav-case-active {
    border-bottom: 3px solid #3c8fcf;
    color: #3c8fcf;
}

.case-list {
    margin: 30px 0;
}

#list {
    display: flex;
    justify-content: flex-start;
    flex-wrap: wrap;
    align-content: start;
    margin-top: 20px;
}

#list li {
    margin: 0 30px 30px 0;
    position: relative;
    font-size: 18px;
    text-align: center;
    color: #333333;
    cursor: pointer;
}

#list .item-text {
    margin-top: 10px;
}
#list li .item-mask {
    position: absolute;
    background-color: rgba(0, 153, 255, 0.4);
    left: 0;
    top: 0;
    margin-top: 0;
    width: 360px;
    height: 240px;
}
#list li:hover .item-mask {
    display: none;
}
.list-image {
    width: 360px;
    height: 240px;
}