body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

#calendar {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    
    width: calc(7 * 70px);

    margin-bottom: 5px;
}

.calendar-day {
    width: 70px;
    height: 60px;

    border: 1px solid black;
    border-collapse: collapse;

    box-sizing: border-box;
}

.calendar-day::after {
    content: var(--day);

    padding: 5px;

    color: gray;
}


.calendar-day.active {
    background-color: rgba(255, 255, 0, 0.166);
}

.calendar-day.old {
    opacity: 0;
}