.tooltip-chart {
    position: absolute;
    width: 40px;
    height: 20px;
    padding: 5px;
    background-color: white;
    opacity: 0.7;
    border-radius: 5px;
    border: 1px solid #000;
    pointer-events: none;
    display: none;
    font-family:  "PT Sans", Arial, Helvetica, sans-serif; 
    font-size: 15px;
    font-weight: bold;
    text-align: center;
}