index.css

html
{
	height: 100%;
	overflow: hidden;
}

body
{
	display: flex;
	margin: 0px;
	height: 100%;
	flex-direction: column;
}

#game-area
{
	flex: 1;
	width: 100%;
	height: 100%;
}

#controls
{
	background-color: #f2f2f2;
}

.button
{
	display: inline-block;
	width: 13%;
	padding-top: 13%;
}

.up-button
{
	background: transparent url("up.png") no-repeat center/contain;
}

.down-button
{
	background: transparent url("down.png") no-repeat center/contain;
}

.left-button
{
	background: transparent url("left.png") no-repeat center/contain;
}

.right-button
{
	background: transparent url("right.png") no-repeat center/contain;
}

#start-button
{
	background: transparent url("start.png") no-repeat center/contain;
}

#stop-button
{
	background: transparent url("stop.png") no-repeat center/contain;
}

#clear-button
{
	background: transparent url("clear.png") no-repeat center/contain;
}