style.css

body {
  font-family: 'Montserrat', sans-serif;
  background: #bba7b3;
}
#container {
  background-color: #bba7b3;
  margin: 20px auto;
}
#calculator {
  width: 320px;
  height: 520px;
  margin: 0 auto;
  top: 20px;
  position: relative;
  border-radius: 19px;
  background: #ad9ba6;
  box-shadow:  -50px 50px 58px #9f8f99, 50px -50px 58px #bba7b3;
}
#result {
  height: 120px;
}
#keyboard {
  height: 400px;
}
#history{
  text-align: right;
  height: 20px;
  margin: 0 20px;
  padding-top: 20px;
  font-size: 15px;
  color: #334944;
}
#output {
  text-align: right;
  height: 20px;
  margin: 10px 20px;
  font-size: 30px;
}
.operator, .number, .empty{
	width: 50px;
	height: 50px;
	margin: 15px;
	float: left;
	border-radius: 50%;
	border-width: 0;
	font-weight: bold;
	font-size: 15px;
}
.number, .empty{
	background: none;
}
.number, .operator{
	cursor: pointer;
}
.operator:active, .number:active{
	font-size: 13px;
}
.operator:focus, .number:focus, .empty:focus{
	outline: 0;
}
button:nth-child(4){
	font-size: 20px;
	background-color: #20b2aa;
}
button:nth-child(8){
	font-size: 20px;
	background-color: #ffa500;
}
button:nth-child(12){
	font-size: 20px;
	background-color: #f08080;
}
button:nth-child(16){
	font-size: 20px;
	background-color: #7d93e0;
}
button:nth-child(20){
	font-size: 20px;
	background-color: #9477af;
}