* {
      box-sizing: border-box;
      font-family: "Poppins", sans-serif;
    }

    body {
      background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
      height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
      margin: 0;
    }

    .calculator {
      background-color: #1b1b1b;
      border-radius: 20px;
      box-shadow: 0 4px 25px rgba(0, 0, 0, 0.4);
      padding: 25px;
      width: 350px;
      text-align: center;
      color: #fff;
    }

    h1 {
      color: aqua;
      text-transform: uppercase;
      letter-spacing: 2px;
      margin-bottom: 20px;
    }

    #display {
      background-color: #222;
      color: #0ff;
      font-size: 2.2rem;
      border-radius: 12px;
      padding: 15px;
      text-align: right;
      overflow-x: auto;
      margin-bottom: 20px;
      min-height: 50px;
    }

    .button-grid {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 10px;
    }

    button {
      background-color: #333;
      border: 2px solid #00ffff;
      border-radius: 12px;
      color: #fff;
      font-size: 1.3rem;
      padding: 15px;
      cursor: pointer;
      transition: 0.2s;
    }

    button:hover {
      background-color: #00ffff;
      color: #000;
      transform: scale(1.05);
    }

    .operator {
      color: #00ffff;
      font-weight: bold;
    }

    .equals {
      background-color: #00ffff;
      color: #000;
      font-weight: bold;
      grid-column: span 2;
    }

    .clear {
      background-color: #ff4757;
      grid-column: span 2;
      border-color: #ff4757;
    }

    .delete {
      background-color: #ffa502;
      color: #000;
    }

    @media (max-width: 400px) {
      .calculator {
        width: 90%;
      }
    }