*{
    margin: 0px;
}
.topnav{
    background: #123;
    overflow: hidden;
}

.topnav a{
    color: white;
    text-decoration: none;
    font-size: 18px;
    padding: 15px 20px;
    text-align: center;
    display: block;
    float: left;
}
.topnav a:hover{
    color: black;
    background: #ddd;

}

.topnav a.active{
    background: #00aa00;
}

.topnav .icon{
    display: none;
}

@media screen and (max-width:600px){
    .topnav a:not(:first-child) {
        display: none;
    }
    .topnav a.icon{
        float: right;
        display: block;
    }

    .topnav.responsive{
        position: relative;
        } 
    .topnav.responsive a.icon{
        position: absolute;
        top: 0px;
        right: 0px;
    } 
    .topnav.responsive a{
        display: block;
        float:none;
        text-align: left;
    } 
    
}