stylesheet.css

.calculator{
	text-align: center;
	margin: 0 auto;
	padding-top: 100px;
	width: 400px;
}

.calculator-screen{
	width: 100%;
	height: 100px;
	background-color: #252525;
	color: #fff;
	text-align: right;
	font-size: 36px;
	border: none;
	padding: 0 20px;
	box-sizing: border-box;
}

.calculator-keys{
	width: 100%;
}

.row{
	display: flex;
}

button{
	height: 80px;
	background-color: gray;
	border: 1px solid black;
	font-size: 36px;
	color: #fff;
	width: 100%;
	outline: none;
}

.all-clear, .number.zero-btn {
	width: 50%;
}

.percentage {
	width: 25%;
}

.number, .decimal {
	width: 25%;
}

.operator, .equal-sign {
	width: 25%;
	background-color: orange;
}

button:hover{
	background-color: darkgray;
}

.operator:hover, .equal-sign:hover {
	background-color: darkorange;
}