#btn-know:hover {
    border: none;
    background-color: #76ff7b42;
    color: #4CAF50
}

#btn-dont-know:hover {
    border: none;
    background-color: rgba(235, 235, 0, 0.203);
    color: rgb(185, 185, 0);
}

#btn-hard:hover {
    border: none;
    background-color: rgba(255, 0, 0, 0.277);
    color: red;
}
.btn-know {
    border: none;
    background-color: #76ff7b42;
    color: #4CAF50
}

.btn-dont-know {
    border: none;
    background-color: rgba(235, 235, 0, 0.203);
    color: rgb(185, 185, 0);
}

.btn-hard {
    border: none;
    background-color: rgba(255, 0, 0, 0.277);
    color: red;
}