Hi I was wondering how do I build over a level 1 fortification to a higher level? I am trying to build over a level 1 wall but it won't let me. Is there like a requirement of some sort like you have to have your whole wall completed or something before you can move on to the next level? Or do I just destroy it and lose the rubies I used to build it to build a higher level fortification? I have a mix of level 2 and 1 stuff in my haven but the whole wall is only half way completed.