Actually, a great app, but after my fortress Lev.7 reaches me to install an update, and will refer to Amazon App Store. In this none is stored and can only start the app there. This requires an update .... a vicious circle. Registering with Amazon Game Circle also does not go. After logging in, I get an error page.
Update: 14/09/2014 Neither Amazon nor app maker support could help and have responded to my request. Each of this app installed and time invested are disappointed from a high level. Can unfortunately only advise.