body {
	background-color: #1f2937;
	color: #fff;
}

.centering {
	display: flex;
	flex-direction: column;
	align-items: center;
}

#main {
	display: grid;
	grid-template-columns: repeat(2, max-content);
	grid-template-rows: repeat(2, max-content);
	gap: 2em;
}

.row {
	margin-top: 0;
	margin-bottom: 0;
}

.invalid {
	color: red;
}

.correct {
	background-color: lime;
}

.wrong-position {
	background-color: yellow;
	color: #000;
}

.cell {
	padding: 0.5em;
	display: inline-block;
	width: 1em;
	height: 1em;
	font-family: monospace;
	font-size: xx-large;
	border: 1px solid #bbb;
	vertical-align: top;
}