@media screen and (max-width: 768px) {
    header {
        display: block;
        flex-direction: column;
        max-height: 1000px;
        transition:all 0.5s;
    }

    .header-menudiv {
        max-height: 0px;
        overflow: hidden;
        margin: 0;
        transition:all 0.4s;
    }

    .header-webtitle {
        margin: 0;
    }

    .header-menubtn {
        display: flex;
        justify-content: center;
        align-items: center;
        width: 50px;
        height: 50px;
        margin: 0 10px 0 0;
    }

    .header-menubtn img {
        width: 80%;
        height: 80%;
    }
}

/* js add class */

.menubtnclick {
    max-height: 1000px;
    overflow: visible;
}