*
{
	margin:0;
	padding:0;
}
body
{
	width:33%;
	height:500px;
	display: flex;
	flex-direction: column;
	margin:auto;
}

#res
{
	background-color:lightgray;
	border: 2px solid black;
	height:48px;
	font-size:20px;
	width:99%;
	padding:10px 0;
}

.btns
{
	padding:auto;

}

#btn0,
#btn1
{
	background-color:lightgreen;
	color:brown;
}

#btnClr,
#btnEql
{
	background-color:darkgreen;
	color:white;
}

#btnSum,
#btnSub,
#btnMul,
#btnDiv
{
	background-color:black;
	color:red;
}

.btn
{
	width:25%;
	height: 36px;
	font-size:18px;
	margin:0;
	float:left;
	text-align: center;
	font-weight: bold;
	border-style:inset;
}