#chart {
    width: 600px;
    margin: 0 auto;
  }
  
  .bar {
    fill: steelblue;
    transition: fill 0.2s ease;
  }
  
  .bar:hover {
    fill: orange;
  }
  
  .tooltip {
    position: absolute;
    background: #333;
    color: #fff;
    padding: 6px 10px;
    font-size: 12px;
    border-radius: 4px;
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.2s;
  }