#startStopBtn{
    color:#FFFFFF;
    background-color:#91c644;
    border:0.15em solid #91c644;
    margin-bottom:1em;
}
#startStopBtn:before{
    content:"Démarrer";
}
#startStopBtn.running:before{
    content:"Annuler";
}
div.testArea{
    margin: 1em;
}