//auxiliary functions for buttons first




@function highlight_border ($c) {
	@return lighten($c, 15%);
}
@function shadow_border ($c) {
	@return darken($c, 10%);
}


@mixin relief($bg, $type:raised, $bc:$bg) {
	// draws a raised (default) or sunken surface
	// $bg: background color for the surface
	// $type: either raised (default) or sunken (or any other value, which makes it sunken)
	// $bc: border color: you may want a different border color (such as an active entry); otherwise it equals $bg
	
	// it only sets background and border colors; color or any other property are not set.
	
	background-color: $bg;
	//border-width: $border_width;
	//border-style: solid;
	@if $type==raised {
		border-left-color: highlight_border($bc);
		border-top-color: highlight_border($bc);
		border-right-color: shadow_border($bc);
		border-bottom-color: shadow_border($bc);
	}
	@else { //usually "sunken", but really anything other than "raised"
		border-left-color: shadow_border($bc);
		border-top-color: shadow_border($bc);
		border-right-color: highlight_border($bc);
		border-bottom-color: highlight_border($bc);
	
	}
}