+ background-position -(@width) y
+// see sprites-rollover
+sprites(image, height, count, h-offset = 0)
+ height: unit(height, px)
+ background: transparent url(image) top left no-repeat;
+ for n in (1..count)
+ &.n{n}
+ y = - (@height * ( n - 1)) - h-offset
+ background-position 0 y