html, body {
    width: 100%;
    height: 100%;
}

@media only screen and (min-width: 800px) {
    section {
        background-color: white;
        /*padding-top: 50px;*/
        width: 100%;
        margin-top: -20px;
    }

    .about_top {
        background: url("../images/about_bg_s.jpg") no-repeat center center;
        background-size: cover;
        height: 46rem;
        background-repeat: no-repeat;
    }

    .top_title {
        padding-top: 15rem;
        color: #ecfffc;

    }

    .top_title > h2 {
        font-size: 1.5rem;
        text-align: center;
        line-height: 2rem;
        font-weight: 600;
        letter-spacing: 5px;
    }

    .top_title > p {
        text-align: center;
        font-size: 20px;
        line-height: 1.5rem;
        font-weight: 700;
        padding-top: 1rem;
    }

    .com_intro {
        padding: 8rem 0;
    }

    .intro_title > h2 {
        margin: 0;
        text-align: center;
        font-size: 1.5rem;
        font-weight: 700;
    }

    .intro_title > i {
        text-align: center;
        display: block;
        font-size: .8rem;
        line-height: 2rem;
    }

    .intro_content {
        padding: 2% 20% 0 20%;
    }

    .intro_content > p {
        color: #474a4d;
        font-size: .8rem;
        text-align: justify;
        margin: 0;
    }

    .history {
        background-image: url("../images/history.jpg");
        background-size: cover;
        padding: 2% 0;
    }

    .history_title > h2 {
        text-align: center;
        font-size: 1.5rem;
        font-weight: bold;
        color: whitesmoke;
    }

    .contact {
        padding: 5% 0 1% 0;
        background-color: whitesmoke;
    }

    .contact_title {
        font-weight: 600;
        font-size: 1.5rem;
        text-align: center;
        color: #409EFF;
    }

    .contact_top > p {
        text-align: center;
        color: #909399;
    }

    .mdn-footer > span {
        display: block;
        padding: 10px 0;
        color: #909399;
    }

    .certificate_inner > span {
        display: block;
        font-size: 1.5rem;
        text-align: center;
        font-weight: 600;
        letter-spacing: 5px;
    }

}

@media only screen and (max-width: 800px) {
    section {
        background-color: white;
        /*padding-top: 50px;*/
        width: 100%;
        margin-top: -20px;
    }

    .about_top {
        background: url("../images/m_about_bg.jpg") no-repeat center center;
        background-size: cover;
        height: 20rem;
        background-repeat: no-repeat;
    }

    .top_title {
        padding-top: 50%;
        color: #ecfffc;

    }

    .top_title > h2 {
        font-size: 1.2rem;
        text-align: center;
        line-height: 1.5rem;
        font-weight: 600;
    }

    .br_2 {
        display: none;
    }

    .top_title > p {
        text-align: center;
        font-size: .6rem;
        line-height: 1rem;
        font-weight: 700;
        padding-top: 1rem;
    }

    .com_intro {
        padding: 2rem 0;
    }

    .intro_title > h2 {
        margin: 0;
        text-align: center;
        font-size: 1rem;
        font-weight: 700;
    }

    .intro_title > i {
        text-align: center;
        display: block;
        font-size: .5rem;
        line-height: 1rem;
    }

    .intro_content {
        padding: 2% 10%;
    }

    .intro_content > p {
        color: #474a4d;
        font-size: .6rem;
        text-align: justify;
        margin: 0;
    }

    .history {
        display: none;
    }

    .contact {
        background: whitesmoke;
        padding: 8% 0 0 0;
        margin-bottom: -15%;
    }

    .contact_title {
        font-size: 1rem;
        text-align: center;
        font-weight: 600;
        color: #409EFF;;
    }

    .contact_top > p {
        text-align: center;
        color: #909399;
        font-size: .5rem;
        padding-top: 2%;
        margin-bottom: -20px;
    }

    .mdn-footer > span {
        display: block;
        padding-top: 10px;
        color: #909399;
        font-size: .6rem;
    }
}