In Beyond Ynth (and Beyond Ynth HD for the iPad), you play as Kribl, a chipper little insect who solves puzzles in four brightly animated worlds. But don't let the cutesy look fool you - these puzzles are tough.
Maybe it's just because I'm used to playing iPhone games that only require half my attention while I'm trying to keep from bumping into people on the train, but Beyond Ynth's unique brand of puzzles - basically tipping big blocks from one side to the next to strategically gain access to platforms and openings - require not only some precise tapping but some serious planning too. This helpful video from TouchArcade gives a good overview of the gameplay:
It can get frustrating at times - like when you tip a block one time too many, closing off some crucial entry point and forcing you to replay the entire level - but the puzzles are so cleverly constructed that you never have that sinking feeling that you have outsmarted the developer.
FDG Entertainment, the group behind the game, claims that it was "one year in the making", and while the graphics are very nice and the game has a high level of polish (nice little narrative, pleasant music, etc), it definitely seems like a good amount of that time went into making sure the levels were tough enough to truly be challenging.
It'd be nice if it was a universal app, but such is life - Beyond Ynth is $5 and Beyond Ynth HD is $8. [iTunes]