Would be better if it weren't for the forced ad breaks. I waste enough time not watching ads to get free items. Also, the ads they show are misleading. I've made the mistake of trying two apps advertised, and they didn't match the ads. (bait and switch) Also, it is sometimes difficult to see exactly where you are dropping items (finger in the way), so sometimes it merges 3, when you are trying to setup a 4 merge. This can be really frustrating. Please add an undo button, or ask for conformation.