#calculator {
  width: 300px;
  margin: 0 auto;
  text-align: center;
  border: 1px solid #ccc;
  border-radius: 5px;
}

#result {
  width: 85%;
  margin-top: 10px;
  margin-bottom: 10px;
  padding: 10px;
  font-size: 20px;
  text-align: right;
  border: 1px solid #ccc;
  border-radius: 5px;
}

input[type="button"] {
  width: 60px;
  height: 60px;
  margin: 5px;
  font-size: 20px;
  border: none;
  border-radius: 5px;
  background-color: #eee;
  cursor: pointer;
}

input[type="button"]:hover {
  background-color: #ddd;
}

input[value="="] {
  background-color: #f90;
  color: #fff;
}