#stacks_in_2 {
	background-color: rgba(0, 0, 0, 0.30);
	margin:  20px;
}

#stacks_in_4 {
	background-color: rgba(0, 0, 0, 0.30);
	margin:  20px;
}

#stacks_in_6 {
	background-color: rgba(0, 0, 0, 0.30);
	margin:  20px;
}