.calculator {
    max-width: 200px;
    margin: 0 auto;
    text-align: center;
  }
  
  #result {
    width: 100%;
    height: 40px;
    margin-bottom: 10px;
    font-size: 20px;
    text-align: right;
  }
  
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 5px;
  }
  
  button {
    width: 100%;
    height: 40px;
    font-size: 18px;
  }