.main-bg {
    background-image: url('../images/bg-mb.png');
    background-size: cover;
    padding-bottom: 60px;
}
@media screen and (min-width: 640px) {
    .main-bg {
        background-image: url('../images/bg-pc.png');
    }
}

.factory-tour {
    padding-top: 120px;
}
.about-img {
    width: 75%;
    margin: 0 auto;
}
@media screen and (min-width: 1200px) {
    .about-img {
        width: 40%;
        max-width: 600px;
    }
    .about-introduce:nth-of-type(odd) .about-img {
        float: left;
        margin: 0 40px 20px 0;
    }
    .about-introduce:nth-of-type(even) .about-img {
        float: right;
        margin: 0 0 20px 40px;
    }
}

.technical-introduction .about-introduce {
    margin-bottom: 30px;
}
@media screen and (min-width: 1200px) {
    .technical-introduction .about-introduce {
        margin-bottom: 60px;
    }
}
.technical-introduction .about-introduce:last-child {
    margin-bottom: 0px;
}

@media screen and (min-width: 1200px) {
    .about-introduce {
        min-height: 300px;
    }
}


@media screen and (min-width: 1200px) {
    .about-content {
        width: 100%;
        padding-top: 10px;
    }
    .about-content .brd-l-title {
        font-size: 24px;
    }
}
@media screen and (min-width: 1200px) {
    .about-description {
        padding-top: 30px;
        line-height: 1.9;
    }
}