body {
      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen,
        Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
      background-color: #fff;
      color: #333;
      padding: 2rem;
      margin: auto;
    }

    h2 {
      margin-top: 0;
    }

    #drop-area {
      border: 1px dashed #ccc;
      padding: 2rem;
      text-align: center;
      transition: background 0.2s ease;
    }

    #drop-area.hover {
      background-color: #f5f5f5;
    }

    #tree-output {
      white-space: pre;
      background-color: #f9f9f9;
      padding: 1rem;
      overflow-x: auto;
      margin-top: 1rem;
      font-family: monospace;
      font-size: 14px;
      line-height: 1.6;
    }

    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      margin-top: 1rem;
      flex-wrap: wrap;
    }

    label {
      font-size: 14px;
    }

    button {
      background-color: transparent;
      border: 1px solid #ccc;
      padding: 0.4rem 0.8rem;
      cursor: pointer;
      font-size: 14px;
      transition: background 0.2s ease;
    }

    button:hover {
      background-color: #eee;
    }