Cardboard Castle isn't without its problems to be sure, and some of them are bigger than others. But I think the look and feel of the game make up for those issues for the most part. It's a short but enjoyable ride that's definitely worth the price.
Overall, I think Cardboard Castle is an amusing game for what it is. If you like trial and error type of games, funny visual effects, and something with a storybook charm, I suggest getting this app which at $0.99 is reasonably priced.