Definitely one of the better games I've played on here in a while. It managed to be very simple and very complex at the same time, which is a pretty impressive feat.
This is one of the most original game concepts I have seen this year.
Difficulty is well-balanced, graphics are nice, game play is smooth.
how to complete the 4th stage
You always can use walkthrough (the question mark icon in the lower right corner).
quite entertaining puzzle!