.container {
    max-width: 400px;
    margin: 0 auto;
    padding: 20px;
  }
  
  h1, h2 {
    text-align: center;
  }
  
  form {
    margin-bottom: 20px;
  }
  
  label {
    display: block;
    margin-bottom: 5px;
  }
  
  input[type="number"] {
    width: 100%;
    padding: 5px;
    margin-bottom: 10px;
  }
  
  input[type="submit"] {
    width: 100%;
    padding: 10px;
    background-color: #4CAF50;
    color: white;
    border: none;
    cursor: pointer;
  }
  
  .hidden {
    display: none;
  }