These were really fun. The puzzles are interesting and varied, some requiring "out of the box" thinking. I appreciated how the game did not hold my hand through solving the levels, and let me play around until I had a breakthrough.
You don't have to worry about becoming stuck, however, as there is a robust hint system that will nudge you in the right direction.
As for controls and usability, I can't really talk about them without spoiling something. But, there is at least one puzzle that requires sound and another that needs to have multi-touch gestures disabled.