body {
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background: linear-gradient(135deg, #e3f2fd, #bbdefb);
      height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      margin: 0;
}

.calculator-container {
      background: white;
      padding: 30px 40px;
      border-radius: 16px;
      box-shadow: 0 4px 20px rgba(0,0,0,0.15);
      width: 340px;
      text-align: center;
}

.calculator-container h1 {
      margin-bottom: 25px;
      color: #1976d2;
      font-size: 26px;
}

input {
      width: calc(100% - 20px);
      padding: 10px;
      margin: 8px 0;
      font-size: 16px;
      border: 1px solid #ccc;
      border-radius: 8px;
      outline: none;
      transition: 0.3s;
}

    input:focus {
      border-color: #1976d2;
      box-shadow: 0 0 4px rgba(25, 118, 210, 0.4);
    }

.button-container {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 12px;
      margin-top: 12px;
}

button {
      background: #1976d2;
      color: white;
      font-size: 18px;
      border: none;
      border-radius: 8px;
      padding: 12px;
      cursor: pointer;
      transition: 0.25s;
}

button:hover {
      background: #1565c0;
      transform: scale(1.05);
}

.result-container {
      margin-top: 18px;
      font-size: 18px;
      color: #333;
      font-weight: bold;
      min-height: 24px;
}

#result {
      font-size: 18px;
      color: #777;
      margin-top: 20px;
}