.calculator {
  width: 300px;
  margin: 100px auto;
  border: 1px solid #ccc;
  border-radius: 5px;
  padding: 10px;
}

.display {
  width: calc(100% - 20px);
  margin-bottom: 10px;
  padding: 5px;
}

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

button {
  padding: 10px;
  font-size: 16px;
  cursor: pointer;
}

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