body {
      display: flex;
      justify-content: center;
      align-items: center;
      height: 100vh;
      background: #f0f0f0;
      font-family: 'Poppins', sans-serif;
    }

    .calculator {
      background: #1e1e1e;
      padding: 30px;
      border-radius: 25px;
      box-shadow: 0 8px 25px rgba(0,0,0,.4);
      width: 340px;
    }

    .display {
      background: #000;
      color: #0f0;
      font-size: 2.2rem;
      text-align: right;
      padding: 20px;
      border-radius: 12px;
      margin-bottom: 25px;
      overflow-x: auto;
    }

    .buttons {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 18px;
    }

    button {
      padding: 22px;
      font-size: 1.4rem;
      border: none;
      border-radius: 14px;
      cursor: pointer;
      transition: .2s;
      font-weight: 700;
    }

    button:hover {
      transform: scale(1.08);
      box-shadow: 0 5px 15px rgba(0,0,0,.3);
    }

    .operator {
      background: #ff9f43;
      color: #fff;
    }

    .equal, .clear {
      background: #ff9f43;
      color: #fff;
    }

    .number {
      background: #000;
      color: #0f0;
    }