.envelope {
    display: inline-block;
    margin: 10px;
    width: 150px;
    height: 200px;
    border: 1px solid #ccc;
    border-radius: 10px;
    text-align: center;
    position: relative;
  }
  
  .envelope img {
    width: 100px;
    height: 120px;
    margin-top: 10px;
  }
  
  .envelope-number {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 48px;
    font-weight: bold;
    color: red;
    text-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
    z-index: 1;
  }
  
  .envelope-content {
    display: none;
  }
  
  .taken {
    background-color: #ccc;
    pointer-events: none;
  }

  /* .envelope-number {
    font-size: 48px;
    font-weight: bold;
    color: red;
    text-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
    z-index: 1;
  } */
  
  .taken img {
    filter: grayscale(100%);
  }