.marker-cluster {
    border-radius: 20px;
    padding: 5px;
    background-color: rgba(179, 0, 0, .6);
}

.marker-cluster div {
    background-color: #b30000;
    color: #fff;
    text-align: center;
    width: 30px;
    height: 30px;
    line-height: 30px;
    border-radius: 15px;
    font-size: 12px;
    font: 12px;
}