.topnav {
    overflow: hidden;
    background-color: dimgray;
    margin-bottom: 8px;
}

.topnav a {
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    padding: 4px 4px;
    text-decoration: none;
    font-size: 17px;
}

    .topnav a:hover {
        background-color: #ddd;
        color: black;
    }

.active {
    background-color: #4CAF50;
    color: white;
}

.topnav .icon {
    display: none;
}

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

    .topnav a.icon {
        float: right;
        display: block;
    }
}

@media screen and (max-width: 600px) {
    .topnav.responsive {
        position: relative;
    }

        .topnav.responsive .icon {
            position: absolute;
            right: 0;
            top: 0;
        }

        .topnav.responsive a {
            float: none;
            display: block;
            text-align: left;
        }
}