Good Rebus, appealing design, but technical design improvement

In and of itself is a good app. The exercises that you can do for free, be fun and not boring even after repeated playing. But if you want must make comparisons to other players to pay 0.89, would you unlock more courses must also pay back - namely 5,99 per course. That's expensive. In addition, the app constantly jumps (on the Kindle Fire) on the Internet, on the Amazon App page. Probably, so we rated the app. Whether the app so no longer do when you did a review, I have not tried. That the app wants to "force" me to do not like it. Just as the mail that you get when you signed up through his e-mail address. I have the app, because of the sum of the negative reasons, but then removed again.