While the game has no achievements, I ended every level with "perfect" rating, both classic and premium puzzles. It's a color-zone puzzle type, and personally one of the most difficult puzzles I've played. I don't think the game is difficult itself - tho some of the latter puzzles are really devilish. It's just that while I understood the rules easily, and they are easy, I didn't grasp the tricks and whatnots to see how to advance through each puzzle.

So it is also the first game in Steam (and the first one in a loooooong time) where I used the implemented clue system heavily, and I still took me 6h to complete it and so many days because you can only use a limited amount of clues daily. Thankfully there were no achievements - if there was one of "completing the game without using clues" or similar, I would have never completed it. Premium puzzles were interesting, first page was hard but doable without many clues, second was hard only due to the patterns and I didn't use clues, then… The last page of the premium puzzles was a hard chore to finish. But it's an achievement for me, since around the middle of the game I thought I wouldn't finish it, but I did.

Again, I just find it difficult for me. It's a game I can recommend to puzzle lovers.