style.css

   body {
      font-family: Arial, sans-serif;
      margin: 0;
      padding: 0;
      background-color: #f5f5f5;
    }
    
    .container {
      max-width: 600px;
      margin: 50px auto;
      padding: 20px;
      border: 1px solid #ccc;
      border-radius: 5px;
      background-color: #fff;
      box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    }
    
    h1 {
      text-align: center;
      color: #007bff;
    }
    
    label {
      display: block;
      margin-bottom: 5px;
      color: #555;
    }

    input[type="number"] {
      width: 100%;
      padding: 10px;
      border: 1px solid #ccc;
      border-radius: 5px;
      margin-bottom: 10px;
      font-size: 16px;
    }

    select {
      width: 100%;
      padding: 10px;
      border: 1px solid #ccc;
      border-radius: 5px;
      margin-bottom: 10px;
      font-size: 16px;
    }

    button {
      display: block;
      width: 100%;
      padding: 12px;
      background-color: #007bff;
      color: #fff;
      border: none;
      border-radius: 5px;
      cursor: pointer;
      transition: background-color 0.3s ease;
    }

    button:hover {
      background-color: #0056b3;
    }

    .result {
      margin-top: 20px;
      font-size: 18px;
    }