.tit-nav-li:nth-child(4) {
    background-color: #638df9;
}

.tit-nav-li:nth-child(4) a {
    color: white;
}

.ban-tit {
    width: 100%;
    height: 300px;
    background: url("../upload/case.png") no-repeat;
    background-size: 100%;
    overflow: hidden;
    margin-bottom: 30px;
}

.bg-tit {
    width: 300px;
    height: 100px;
    text-align: center;
    margin: 0 auto;
    margin-top: 70px;
}

.bg-tit h2 {
    width: 300px;
    height: 50px;
    line-height: 50px;
    font-size: 36px;
    font-weight: 300;
    color: white;
    letter-spacing: 5px;
}

.bg-tit h3 {
    width: 300px;
    height: 35px;
    line-height: 35px;
    font-size: 18px;
    font-weight: 300;
    color: white;
    letter-spacing: 2px;
}

.trade {
    width: 90%;
    margin: 0 auto;
    margin-bottom: 30px;
}

.trade-list {
    float: left;
    width: 15%;
    height: 40px;
    padding: 5px 0;
    text-align: center;
    line-height: 40px;
    font-size: 20px;
    color: #57acfa;
    border-radius: 5px;
    border: 2px solid #57acfa;
    margin-left: 4%;
    margin-bottom: 15px;
    cursor: pointer;
    overflow: hidden;
}

.trade-list-current {
    background-color: #57acfa;
    color: white;
}

.case-show {
    width: 85%;
    margin: 0 auto;
}

.opt-show {
    display: none;
}

.show-box {
    break-inside: avoid;
    box-sizing: border-box;
    padding: 10px;
    border: 1px solid #ccc;
    margin-bottom: 10px;
}

.show-box-pic {
    margin-bottom: 10px;
}

.show-box-pic img {
    width: 100%;
}

.pic-tit {
    width: 100%;
    text-align: center;
    line-height: 30px;
    font-size: 24px;
    color: black;
}

@media (min-width:480px) {
    .opt-box {
        column-count: 2;
        column-gap: 10px;
    }
}

@media (min-width:960px) {
    .opt-box {
        column-count: 3;
        column-gap: 10px;
    }
}

@media (min-width:1200px) {
    .opt-box {
        column-count: 4;
        column-gap: 10px;
    }
}

@media (min-width:1660px) {
    .opt-box {
        column-count: 5;
        column-gap: 10px;
    }
}