Hi-res Sprite Sheet Mixin, integrating with Sass Breakpoint

sprite.scss

@mixin sprite($icon-name, $important: '') {
    
    @if $important != '' {
        // @1x resolution screens
        background-image: sprite-url($sprite-pri) !important;
        background-position: sprite-position($sprite-pri, $icon-name) !important;
        
        // @2x resolution screens
        @include breakpoint($hi_res) {
            background-image: sprite-url($sprite-pri--2x) !important;
            @include background-size(rem(sprite-width($sprite-pri--2x) / 2) rem(sprite-height($sprite-pri--2x) / 2));
            background-position: round(nth(sprite-position($sprite-pri--2x, '#{$icon-name}@2x'), 1) / 2) round(nth(sprite-position($sprite-pri--2x, '#{$icon-name}@2x'), 2) / 2) !important;
        }
        
        // Print out the icon dimensions
        width: rem(image-width('sprite--pri/#{$icon-name}.png')) !important;
        height: rem(image-height('sprite--pri/#{$icon-name}.png')) !important;
    }
    
    @else {
        // @1x resolution screens
        background-image: sprite-url($sprite-pri);
        background-position: sprite-position($sprite-pri, $icon-name);
        
        // @2x resolution screens
        @include breakpoint($hi_res) {
            background-image: sprite-url($sprite-pri--2x);
            @include background-size(rem(sprite-width($sprite-pri--2x) / 2) rem(sprite-height($sprite-pri--2x) / 2));
            background-position: round(nth(sprite-position($sprite-pri--2x, '#{$icon-name}@2x'), 1) / 2) round(nth(sprite-position($sprite-pri--2x, '#{$icon-name}@2x'), 2) / 2);
        }
        
        // Print out the icon dimensions
        width: rem(image-width('sprite--pri/#{$icon-name}.png'));
        height: rem(image-height('sprite--pri/#{$icon-name}.png'));
    }
}