.calculator {
  max-width: 300px;
  margin: 0 auto;
  padding: 20px;
  background-color: #f9f9f9;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

input[type="text"] {
  width: calc(100% - 10px);
  padding: 15px;
  margin-bottom: 20px;
  border: 2px solid #ccc;
  border-radius: 10px;
  font-size: 24px;
  text-align: right;
  outline: none;
}

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

button {
  padding: 20px;
  font-size: 20px;
  background-color: #4CAF50;
  color: #fff;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.3s ease;
}

button:hover {
  background-color: #45a049;
}

button.clear {
  background-color: #f44336;
}

button.clear:hover {
  background-color: #d32f2f;
}