body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #f0f2f5;
    font-family: Arial, sans-serif;
    background: linear-gradient(black, white, blue);
    
  }
  
  .calculator {
    background: black;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
    width: 350px;
    
  }
  
  #display {
    width: 95%;
    height: 70px;
    font-size: 24px;
    text-align: right;
    margin-bottom: 15px;
    padding: 10px;
    border: 2px solid #ccc;
    border-radius: 8px;
    
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    
  }
  
  button {
    padding: 20px;
    font-size: 18px;
    border:2px solid blue ;
    border-radius: 10px;
    background: white;
    cursor: pointer;
    transition: background 0.3s ease;
    
   

  }
  
  button:hover {
    background: blue;
    color: white;
    
  }
  
  .zero {
    grid-column: span 2;
  }