html, body {
    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;
    /* margin-top:; */
}
#description_div
{
    /* background-image: url('picture/HD_Text_BG.png'); */
    /* background-repeat: no-repeat; */
    max-width:560px;
    max-height:280px;
    height: 280px;
    float:right;
    padding-top: 23%;
    padding-left: 150px;
    /* padding-top: 50%;
    padding-left: 50%; */
    /* margin-top:30%;
    margin-left:30%;  */
    color: black;
}
#identity_div
{
    /* padding-left:20%; */
    width:500px; 
    /* float: left; */
    /* height:100%; */
    /* margin-left: 100%; */
    margin-top:60%;
    margin-right: 30%;
}
#role{
    max-width: fit-content;
    margin-top:0px;
    margin-left: auto;
    margin-right: auto;
}
#teacher_btn
{
    background-color: #0071BC;
    padding-left:60px;
    padding-right:60px;
    font-size: 28px;
    color: white;
}

#student_btn
{
    background-color: #29ABE2;
    padding-left:60px;
    padding-right:60px;
    font-size: 28px;
    color: white;
}

.language_link
{
    font-size:20px;
}

/* #decription_text
{
    width: -moz-fit-content;
    width: fit-content;
} */


/* phone size */
@media all and (max-width: 480px) 
{
    #description_div
    {
        width: 100%;
        /* margin-top:0%;
        padding-left: 0%;
        padding-top:10%;
        padding-bottom:10%; */
    }

    #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:0px;
        margin-left: auto;
        margin-right: auto;
        flex-wrap: wrap;
    }
    h1{
        font-size:30px;
    }

    h4{
        font-size:20px;
    }

    .language_link
    {
        font-size:15px;
    }
}

/* tablet size */
@media all and (max-width: 780px)
{
    #description_div
    {
        /* width: 100%; */
        margin-left: auto;
        margin-right: auto;
        margin-bottom: auto;
        /* margin-top:0%;
        padding-left: 0%;
        padding-top:20%;
        padding-bottom:20%; */
    }
    #identity_div
    {
        width: 100%;
        margin-left: 0%;
        margin-top:400px;
        /* margin-bottom:10%; */ 
    }
    #role{
        max-width: fit-content;
        margin-top:0px;
        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:0px;
    }
}