.tab {
     background-color: none;
     font-size: var(--fs-sm);
     height:100%;
     display: inline-block;
     padding:1em;
    vertical-align:middle;
}

.tab:hover:not(.selected-tab) {
    background-color: #223; 
}

.header {
    position:fixed;
    top:0;
    width:100%;
    opacity:1;
    z-index:1000;
    background-color: #223;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    display: flex;
    flex-wrap:nowrap;
    overflow-x:auto;
    overflow-y:hidden;
    -webkit-overflow-scrolling: touch;
}

.header > * {
    flex: 0 0 auto;
    white-space: nowrap;
}

.tab:first-of-type { padding-left:1em }

.selected-tab {
    background-color: #55f;
}