If you want to get rounded corners on an hbox, instead of
:first-child {
border-top-left-radius: 5px;
border-bottom-left-radius: 5px;
}
:last-child {
border-top-right-radius: 5px;
border-bottom-right-radius: 5px;
}
you now need to write:
:first-child, :last-child:dir(rtl) {
border-top-left-radius: 5px;
border-bottom-left-radius: 5px;
}
:last-child, :first-child:dir(rtl)
{
border-top-right-radius: 5px;
border-bottom-right-radius: 5px;
}