Koala Free Gift BOGO Upsell

I was looking for an app that would add a product when customers purchased a product from a collection. I wanted the offer to apply as many times as qualifying products were purchased and remove it if they removed it. I tried around 7 apps before finding Koala. It increases as they add more and also removes the free items as they remove the qualifying product. I haven't tried any of the other promotions yet, but it works perfectly for this one!