table {
    width: 50%;
    margin: 10px auto 10px auto;
    font-size: 18px;
    font-weight: bold;
    text-align: center;
}
table tr td {
    border: 1px solid black;
}
td {
    padding: 16px;
    cursor: pointer;
}
.not-done:hover {
    background-color: rgba(30, 144, 255, 0.3);
}
.selected {
    background: rgba(30, 144, 255, 1);
}
.correct {
    cursor: default;
    background: rgba(30, 144, 255, 1);
}
.otree-btn-next {
    display: none;
}