table.dataTable td.dt-control {
    text-align: center;
    cursor: pointer;
}

table.dataTable td.dt-control:before {
    display: inline-block;
    color: rgba(0, 0, 0, 0.5);
    content: "►";
}

table.dataTable tr.shown td.dt-control:before {
    content: "▼";
}