<div class="calendar">
    <div class="calendar__title">
        October 2019
    </div>
    <div class="calendar__wrapper">
        <div class="calendar__inner">
            <span class="calendar__item calendar__week_day">Mon</span>
            <span class="calendar__item calendar__week_day">Tue</span>
            <span class="calendar__item calendar__week_day">Wed</span>
            <span class="calendar__item calendar__week_day">Thu</span>
            <span class="calendar__item calendar__week_day">Fri</span>
            <span class="calendar__item calendar__week_day">Sat</span>
            <span class="calendar__item calendar__week_day">Sun</span>
            <span class="calendar__item"></span>
            <span class="calendar__item"></span>
            <span class="calendar__item"></span>
            <span class="calendar__item"></span>
            <span class="calendar__item"></span>
            <span class="calendar__item">1</span>
            <span class="calendar__item">2</span>
            <span class="calendar__item">3</span>
            <span class="calendar__item">4</span>
            <span class="calendar__item">5</span>
            <span class="calendar__item">6</span>
            <span class="calendar__item">7</span>
            <span class="calendar__item">8</span>
            <span class="calendar__item">9</span>
            <span class="calendar__item">10</span>
            <span class="calendar__item">11</span>
            <span class="calendar__item">12</span>
            <span class="calendar__item">13</span>
            <span class="calendar__item">14</span>
            <span class="calendar__item">15</span>
            <span class="calendar__item">16</span>
            <span class="calendar__item calendar__item_active">17</span>
            <span class="calendar__item calendar__item_between-active">18</span>
            <span class="calendar__item calendar__item_between-active">19</span>
            <span class="calendar__item calendar__item_between-active">20</span>
            <span class="calendar__item calendar__item_between-active">21</span>
            <span class="calendar__item calendar__item_active">22</span>
            <span class="calendar__item">23</span>
            <span class="calendar__item">24</span>
            <span class="calendar__item">25</span>
            <span class="calendar__item">26</span>
            <span class="calendar__item">27</span>
            <span class="calendar__item">28</span>
            <span class="calendar__item">29</span>
            <span class="calendar__item">30</span>
            <span class="calendar__item">31</span>
        </div>
    </div>

</div>
                            

.calendar {
    box-sizing: border-box;
    background: var(--main-bg-color);
    border: 1px solid var(--grey-3);
    border-radius: 0.5em;
    padding: 1.5em 1.625em 1.5em 1.625em;

    max-width: 304px;
    width: 100%;
    display: inline-block;
}

.calendar__wrapper {
    position: relative;
    padding-bottom: 100%;
}

.calendar__title {
    font-family: 'Inter', sans-serif;
    font-style: normal;
    font-weight: 600;
    font-size: 1.2em;
    line-height: 1.5em;
    color: var(--dark-blue);
    text-align: center;
    margin-bottom: 1.5em;
}

.calendar__item {
    display: flex;
    justify-content: center;
    align-items: center;
    font-family: 'Source Sans Pro', sans-serif;
    font-style: normal;
    font-weight: 400;
    font-size: 1em;
    line-height: 1.25em;
    color: var(--dark-blue);
}

.calendar__week_day {
    padding-bottom: 0.5em;
    font-family: 'Inter', sans-serif;
    font-size: 0.875em;
    color: var(--grey-6);
}

.calendar__inner {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    grid-template-rows: repeat(7, 1fr);
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}

.calendar__item_active {
    background: var(--ligth-blue);
    color: var(--main-bg-color);
}

.calendar__item_between-active {
    background: rgba(160, 177, 245, 0.2);
}

.calendar_main-page-preview {
    font-size: 10px;
    max-width: 202px;
}

@media screen and (max-width: 768px) {
    .calendar_component_page {
        font-size: 15px;
        max-width: 250px;
    }

    .calendar_main-page-preview {
        font-size: 9px;
        max-width: 164px;
        padding: 0.9em 1.1em 0 1.1em;
        border: transparent;
        transform: scale(0.89);
        transform-origin: top;
    }
}