I really love this game. Even if i found the tutorial rather weak i really got hooked up by this game. This a very special type of puzzle game and not all people may like it so if you're hesitating i would highly recommand you to play the demo first. The difficulty is well-made even if it increases really fast, you start with easy level and you finish with completly insane one.
The only bad point i would have with this game is the story. There is nothing wrong in it but you quicky forget and stop paying attention to it. I played it ~90 hours (+50 not on steam) making it one of the game i played the most.

Update: Now I've played it more than 1000 hours and i'm still liking it.

I really love this game. Even if i found the tutorial rather weak i really got hooked up by this game. This a very special type of puzzle game and not all people may like it so if you're hesitating i would highly recommand you to play the demo first. The difficulty is well-made even if it increases really fast, you start with easy level and you finish with completly insane one. The only bad point i would have with this game is the story. There is nothing wrong in it but you quicky forget and stop paying attention to it. I played it ~90 hours (+50 not on steam) making it one of the game i played the most. Update: Now I've played it more than 1000 hours and i'm still liking it.