I'd say the mechanics of the game are better than your other game - blackjack, because it's less luck dependent. Thinking about where the merged stones are going to go in advance helps. However, it's pretty hardcore. The best I've gotten is one of the top rank stones, but making the second seems really challenging in terms of free space. I don't have the patience to play a hundred times to win, personally :P
Also the programming is good, there aren't any bugs, but it has some performance issues on mobile.