body,
html {
    min-height: 100%
}

#logo {
    margin-top: 1%;
    margin-left: 1%;
    z-index: -1
}

#left-div {
    display: flex;
    flex-wrap: nowrap;
    padding-right: 100px
}

#background {
    background-image: url(picture/HD_BG_2.png);
    background-repeat: no-repeat;
    background-position: center;
    width: 1200px;
    height: 900px;
    background-size: cover
}

#description_div {
    max-width: 560px;
    max-height: 280px;
    height: 280px;
    float: right;
    padding-top: 23%;
    padding-left: 150px;
    color: #000
}

#identity_div {
    width: 500px;
    margin-top: 60%;
    margin-right: 30%
}

#role {
    max-width: fit-content;
    margin-top: 0;
    margin-left: auto;
    margin-right: auto
}

#teacher_btn {
    background-color: #0071bc;
    padding-left: 60px;
    padding-right: 60px;
    font-size: 28px;
    color: #fff
}

#student_btn {
    background-color: #29abe2;
    padding-left: 60px;
    padding-right: 60px;
    font-size: 28px;
    color: #fff
}

.language_link {
    font-size: 20px
}

@media all and (max-width:480px) {
    #description_div {
        width: 100%
    }

    #identity_div {
        width: 100%;
        margin-top: 10%
    }

    #background {
        background-image: url(picture/HD_BG_2.png);
        background-size: cover
    }

    #role {
        max-width: fit-content;
        margin-top: 0;
        margin-left: auto;
        margin-right: auto;
        flex-wrap: wrap
    }

    h1 {
        font-size: 30px
    }

    h4 {
        font-size: 20px
    }

    .language_link {
        font-size: 15px
    }
    .footer {
        min-width: 100%;
        overflow: visible;
        bottom: 0
    }
}

@media all and (max-width:1375px) {
    #description_div {
        margin-left: auto;
        margin-right: auto;
        margin-bottom: auto
    }

    #identity_div {
        width: 100%;
        margin-left: 0;
        margin-top: 400px
    }

    #role {
        max-width: fit-content;
        margin-top: 0;
        margin-left: auto;
        margin-right: auto;
        flex-wrap: wrap
    }

    #background {
        background-image: url(picture/HD_BG_2.png);
        background-size: cover;
        max-width: 100%;
        height: fit-content;
        padding-top: 0;
        padding-bottom: 0;
        display: flex;
        flex-wrap: wrap
    }

    h1 {
        font-size: 30px
    }

    h4 {
        font-size: 20px
    }

    .language_link {
        font-size: 15px
    }

    .footer {
        min-width: 100%;
        overflow: visible;
        bottom: 0
    }
}