Sprite with LESScss from smashing mag

spriteHelpers.less

.spriteHelper(@image, @x, @y, @spriteX, @spriteY) {
   background: url("img/@{image}.png") no-repeat;
   background-position: -(@x*@spriteX) -(@y*@spriteY);
}
.sprite(@image, @x, @y) when (@image = sprite1), (@image = sprite3){
   @spriteX: 32px;
   @spriteY: 16px;
   .spriteHelper(@image, @x, @y, @spriteX, @spriteY);
}
.sprite(@image, @x, @y) when (@image = sprite2){
   @spriteX: 64px;
   @spriteY: 32px;
   .spriteHelper(@image, @x, @y, @spriteX, @spriteY);
}