Does anyone have this zen garden puzzle game?

[Frylock]

http://www.lexaloffle.com/zen.htm

It looks fun, but after having played through the five sample puzzles, I am afraid it will turn out too easy and therefore boring.

Anyone have this game? Opinions? Are there fiendishly tricky ones that tempt you to give up? Or are they all pretty much solvable through a few minutes of trial and error?

-Kris