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

    body {
      min-height: 100vh;
      display: grid;
      place-items: center;
      padding: 20px;
      background: linear-gradient(135deg, #101828, #1d2939);
      color: #f8fafc;
      font-family: "Segoe UI", system-ui, sans-serif;
    }

    .calculator {
      width: min(100%, 340px);
      padding: 22px;
      border: 1px solid rgba(255, 255, 255, 0.14);
      border-radius: 16px;
      background: rgba(255, 255, 255, 0.08);
      box-shadow: 0 24px 70px rgba(0, 0, 0, 0.42);
      backdrop-filter: blur(18px);
    }

    .display {
      width: 100%;
      min-height: 86px;
      display: flex;
      align-items: end;
      justify-content: flex-end;
      overflow: hidden;
      padding: 18px;
      border: 1px solid rgba(255, 255, 255, 0.12);
      border-radius: 12px;
      background: rgba(5, 10, 20, 0.72);
      color: #ffffff;
      font-size: 2rem;
      font-weight: 700;
      word-break: break-all;
    }

    .buttons {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 10px;
      margin-top: 16px;
    }

    button {
      min-height: 58px;
      border: 0;
      border-radius: 12px;
      background: rgba(255, 255, 255, 0.1);
      color: #f8fafc;
      font-size: 1.1rem;
      font-weight: 700;
      cursor: pointer;
      transition: transform 0.18s ease, background 0.18s ease;
    }

    button:hover {
      transform: translateY(-2px);
      background: rgba(255, 255, 255, 0.16);
    }

    button:active {
      transform: translateY(0);
    }

    .operator {
      background: rgba(96, 165, 250, 0.24);
      color: #bfdbfe;
    }

    .clear {
      background: rgba(248, 113, 113, 0.24);
      color: #fecaca;
    }

    .equal {
      grid-column: span 2;
      background: linear-gradient(135deg, #34d399, #60a5fa);
      color: #07111f;
    }

    .zero {
      grid-column: span 2;
    }

    @media (max-width: 380px) {
      .calculator {
        padding: 16px;
      }

      button {
        min-height: 52px;
      }

      .display {
        min-height: 76px;
        font-size: 1.7rem;
      }
    }