panel > border > plate btn:active > border { line-height : 17px; border: 1px #ccc inset; }
panel > border > plate btn:active { border      : 1px #888 inset; }
panel > border > plate btn {
    line-height : 16px;
    background: linear-gradient(178deg, #ccc, #888);  
}

panel > border > plate btn:active {
    line-height : 17px;
    background: linear-gradient(2deg, #ccc, #888);  
}