.blank_cell {
    border: none;
}

td {
    transition: background-color 2s linear;
}


.correct-answer {
    animation-duration: 0.5s;
    animation-name: correct_answer;
}

@keyframes correct_answer {
    from {
        background-color: transparent;
    }

    25% {
        background-color: green;
    }

    to {
        background-color: transparent;
    }
}

#fret_board tr td {
    min-width: 30px;
    /* remove caret*/
    color: transparent;text-shadow: 0 0 0 white;
}

#fret_board tr {
    height: 60px;
}