table {
    border-collapse: collapse;
}

th, td{
    border: 3px solid;
    width: 45px;
    text-align: center;
}

td:hover {
    background-color: gray;
    transition: 0.5s;
}

.not_current_month {
    opacity: 0.3;
}

#current_day {
    background-color: gray;
    color: white;
}

#merging_cells_table td{
    width: 100px;
    height: 100px;
    font-size: 50px;
    font-weight: bold;
}