    # File lib/compass/sass_extensions/functions/sprites.rb, line 146
      def sprite_position(map, sprite = nil, offset_x = ZERO, offset_y = ZERO)
        assert_type offset_x, :Number
        assert_type offset_y, :Number
        sprite = convert_sprite_name(sprite)
        verify_map(map, "sprite-position")
        unless sprite && sprite.is_a?(Sass::Script::String)
          raise Sass::SyntaxError, %Q(The second argument to sprite-position must be a sprite name. See http://beta.compass-style.org/help/tutorials/spriting/ for more information.)
        end
        image = map.image_for(sprite.value)
        unless image
          missing_image!(map, sprite)
        end
        if offset_x.unit_str == "%"
          x = offset_x # CE: Shouldn't this be a percentage of the total width?
        else
          x = offset_x.value - image.left
          x = Sass::Script::Number.new(x, x == 0 ? [] : ["px"])
        end
        y = offset_y.value - image.top
        y = Sass::Script::Number.new(y, y == 0 ? [] : ["px"])
        Sass::Script::List.new([x, y],:space)
      end