html, body {
    height: 100%;
}
#nav {
    width: 250px;
    background-color: #4B4B4B;
    height: 100%;
    left: 0;
    top: 0;
}

#nav_title {
    background-color: #3BAFFA;
    font-size: 1.4rem;
    text-align: center;
    color: white;
    padding: 0.5rem;
    margin: 0;
}

#nav_list{
    list-style: none;
    font-size: 1.5rem;
    color: #FFFFFF;
    border: 0;
    margin: 0;
}

#nav_list > li {
    margin-left: -2.5rem;
    height: 4rem;
}

#nav_list li:hover {
    background-color: #333333;
}


.nav_img {
    margin-top: 1rem;
    margin-left: 1rem;
    display: block;
    float: left;
}

.first_level_text{
    display: block;
    float: left;
    margin-left: 1.2rem;
    font-size: 1.4rem;
    margin-top: 1rem;
}

.up_down {
    display: block;
    float: right;
    margin-right: 3rem;
    margin-top: 1.5rem;
}

.secend_level {
    list-style: none;
    border: 0;
    margin: 0 0 0 -5rem;
    font-size: 1.2rem;
    text-align: center;
    display: none;
}

.secend_level > li {
    height: 3rem;
    font-size: 1.2rem;
    line-height: 3rem;
}

.show {
    display: block;
}