th[data-sort]::after {
    content: ' ↕';
    opacity: .3;
    font-size: .85em;
}

th[data-sort][data-order="asc"]::after {
    content: ' ↑';
    opacity: .9;
}

th[data-sort][data-order="desc"]::after {
    content: ' ↓';
    opacity: .9;
}