Pretty good, but not what it could be.

Overall it works ok. However, there are a few niggles that need addressed.

The first is the apparent requirement that you have at least one gear in place at a time, makes it frustrating when trying to swap between gears that you have to bring one in before the other becomes selectable. Not a big deal but kinda irritating.

Then theres the lack of basic instructions, its simple stuff sure, but its not immediately apparent how to select specific holes in each interior gear. Also why not provide a simple interface to allow the user to specify the number of each teeth per gear and ring?

Finally, one of the things I used to enjoy doing as a kid was to pin down an interior gear and run around it with another interior gear. It provides an additional set of design possibilities and the inanity to do so is a bummer.

Overall a decent job, just wish developers would stop simply creating a digital doppleganger and actually leverage the fact that the iPad is a digital medium. There are so many possibilities in this format why arent we taking it to a whole new level?

Revlis335 about Überdoodle