body {
  font-family: Arial, sans-serif;
  text-align: center;
  background-color: #fafafa;
  padding-top: 50px;
}

#calc {
  display: inline-block;
  border: 2px solid #333;
  padding: 10px;
  border-radius: 10px;
  background: white;
}

#buttons button {
  width: 50px;
  height: 50px;
  margin: 5px;
  font-size: 20px;
}