#calculator {
	width: 400px;
	height: 400px;
	background-color: #607D8B;
	margin-left: auto;
	margin-right: auto;
}

#show_expression {
	max-width: 300px;
	width: 300px;
	font-size: 25px;
	height: 50px;
	line-height: 25px;
	text-align: right;
	color: #FFFFFF;
}

#show_result {
	width: 300px;
	font-size: 20px;
	height: 30px;
	line-height: 20px;
	text-align: right;
	color: #FFFFFF;
}
.cal_key {
	width: 30px;
	height: 30px;
	background-color: #90A4AE;
	text-align: center;
}