Some suggestions for the next version of the iPhone app:

• Content that uses thumbnails of pictures is tedious to use. Click to enlarge (then scroll / zoom to see properly), click "show answer", click again on the picture to actually see the answer because it's covered by the pop-up. Perhaps there's a better solution in v1.1 already? Especially obvious is this problem in the art gallery course.
• The butttons are much too small to use comfortably with a finger. They look like they are designed to be used with a stylus. "Answer", "Didn't know", "Almost" should be at least double the height.

Still - nice to see it on the iPhone and looking forward to future releases.