Thanks for the feedback!
Merge is when you take three of the same item (such as 3 wood rooms, or 3 ballistae for example) and you create one of tier higher from them. Currently you can access it when you selected the item you want to use in merge, then click on the merge icon in the top right corner of the item info panel. If that’s not visible for you make sure you have the latest game version from android google play store or apple iOS app store!
Chain link icons indicate that there is a connection between the materials. One way to use this is if you have heavier materials to the top side and want to make sure your building doesn’t fall over if the lower side gets destroyed.
Any ideas how to add “umph” factor? 🙂