article {
	text-align : center;
}
.board > div {
	display : flex;
}
article .board {
	display : inline-block;
}
.board  span {
	display: inline-block;
	vertical-align:baseline;
	width: 50px;
	height: 50px;
	/*padding : 1em;*/
	margin : 0.1em;
	cursor: pointer;
	border: 1px solid #444;
	/*background: radial-gradient(rgb(150,250,150), #00ee00);*/
}
.board span:hover {
	background: #3AB903;
	background: radial-gradient(rgb(66, 255, 66), #065006);
}

.board span.on {
    background: #009900;
}