@mixin center($xy:xy) {
	@if $xy == xy {
		position: absolute;
		left: 50%;
		top: 50%;
		bottom: auto;
		right: auto;
		@include transform(translateX(-50%) translateY(-50%));
	}
	@else if $xy == x {
		position: absolute;
		left: 50%;
		right: auto;
		@include transform(translateX(-50%));
	}
	@else if $xy == y {
		position: absolute;
		top: 50%;
		bottom: auto;
		@include transform(translateY(-50%));
	}
}