Invent section gets five stars
The Puzzles section is fun until you realize the only way to solve the last one is to solve all the other puzzles in the same sitting, since there is no way to save your progress, as others have noted here. It is a great game for someone in prison, but if you have a life, forget it. Will anyone ever fix that one flaw? Apparently not. The Invent section is the best part of the app anyway. Get in there and just have fun. And the Invent section does let you save your work.
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TinkerBox