* { box-sizing: border-box; margin: 0; padding: 0; }

  html, body {
    width: 100%;
    min-height: 100vh;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: rgba(10, 25, 47, 0.95);
    background-attachment: fixed;
    background-size: cover;
    background-repeat: no-repeat;
    overflow-x: hidden;
  }

  body { display: flex; justify-content: center; align-items: center; padding: 20px; }

  .calculator {
    backdrop-filter: blur(15px);
    background-color: rgba(10, 25, 47, 0.194);
    border-radius: 20px;
    border: 1.2px solid #64ffdb8a;
    box-shadow: 0 0 30px rgba(0, 255, 255, 0.2);
    padding: 20px;
    width: 100%;
    max-width: 400px;
  }

  .calculator-screen {
    width: 100%;
    height: 70px;
    padding: 10px;
    font-size: 2rem;
    background: rgba(4, 41, 96, 0.107);
    border: 1.2px solid #64ffdb8a;
    border-radius: 12px;
    color: #00ffe7;
    text-align: right;
    box-shadow: inset 0 0 5px #00ffff88;
    outline: none;
    margin-bottom: 20px;
  }

  .calculator-keys { display: grid; grid-template-columns: repeat(4, 1fr); gap: 15px; }

  button {
    height: 58px;
    font-weight: 600;
    font-size: 1.2rem;
    border-radius: 15px;
    border: 1.1px solid #00ffee;
    background-color: rgba(10, 25, 47, 0.194);
    color:  #00ffee;
    box-shadow: 0 0 10px #0ff5f9a4, -4px -4px 12px #111;
    transition: all 0.5s ease;
    cursor: pointer;
    width: 98%;
  }

  button:hover { font-weight: 600; background: #00ffe5b9; color: black; font-weight: bold; transform: translateY(-2px); box-shadow: 0 0 15px rgba(0, 255, 255, 0.6); }
  @media screen and (max-width: 480px) {
    .calculator { padding: 15px; border-radius: 15px; }
    .calculator-screen { font-size: 1.5rem; padding: 10px; height: 60px; }
    button { font-size: 1rem; height: 50px; }
    .calculator-keys { gap: 10px; }
  }
  @media screen and (max-width: 320px) { button { font-size: 0.9rem; padding: 6px; } }