.calculator {
  max-width: 300px;
  margin: 0 auto;
  padding: 20px;
  border: 1px solid #ccc;
  border-radius: 5px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

#display {
  width: 100%;
  margin-bottom: 10px;
  padding: 10px;
  font-size: 20px;
  text-align: right;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 5px;
}

button {
  padding: 20px;
  font-size: 18px;
  border: 1px solid #ccc;
  border-radius: 5px;
  background-color: #f9f9f9;
  cursor: pointer;
}

button:hover {
  background-color: #e9e9e9;
}