* { box-sizing: border-box; }

body {
	margin: 0;
	font-family: Arial, sans-serif;
	background: #f2f2f2;
}

.container {
	max-width: 360px;
	margin: 40px auto;
	padding: 16px;
}

.title {
	text-align: center;
	font-size: 20px;
	margin: 0 0 12px;
}

.calculator {
	background: #fff;
	border: 1px solid #ddd;
	border-radius: 10px;
	padding: 14px;
}

.display {
	width: 100%;
	height: 50px;
	font-size: 22px;
	text-align: right;
	padding: 8px 10px;
	border: 1px solid #ccc;
	border-radius: 8px;
	margin-bottom: 12px;
}

.keys {
	display: grid;
	grid-template-columns: repeat(4, 1fr);
	gap: 10px;
}

button {
	height: 46px;
	font-size: 18px;
	border: 1px solid #ccc;
	background: #eee;
	border-radius: 8px;
	cursor: pointer;
}

button:active {
	background: #e0e0e0;
}

.zero {
	grid-column: span 2;
}

.equals {
	background: #3b82f6;
	color: white;
	border-color: #2563eb;
}

.note {
	text-align: center;
	font-size: 12px;
	color: #666;
	margin: 10px 0 0;
}