body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    text-align: center;
    background-color: #f4f4f4;
  }
  
  header {
    background-color: #333;
    color: white;
    padding: 1em 0;
  }
  
  main {
    padding: 2em;
  }
  
  button {
    padding: 0.5em 1em;
    font-size: 1rem;
    cursor: pointer;
  }
  
  /* Popup styles */
  .popup {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
  }
  
  .popup-content {
    background-color: white;
    padding: 2em;
    border-radius: 8px;
    position: relative;
    box-shadow: 0 2px 10px rgba(0,0,0,0.3);
  }
  
  .close {
    position: absolute;
    top: 10px;
    right: 15px;
    font-size: 1.5em;
    cursor: pointer;
  }
  
  .hidden {
    display: none;
  }