body {
    background-color: #222;
}



body > .header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background-color: #222;
}

body > .header > .header-top-nav {
    display: flex;
    justify-content: space-between;
    align-content: center;
    flex-wrap: nowrap;
    align-items: stretch;
}