5 stars: Immediately became addicted. Very easy to learn, but mastery is another thing. I love that there's no real score, other than number of moves (or is it number of checks, I don't really care because it's generally insignificant to the game.) And I appreciate that hints are virtually always available. This is the best of all worlds for me. Don't be surprised if you find that you've lost several hours playing.
5 stars: A lot of complaints that it's impossible to win. The statistics tell me I'm on 39 playing hours and I've won a total of 8 times. I've made 23,820 moves. Some took a week, and one I completed in 24 moves. It's addictive, and entirely winnable if you have the patience. Spending so long on a single game really does make it that bit more satisfying when you do win, though.
3 stars: This game quickly hooked me, and I played for hours upon hours for weeks. However, after spending so much time playing this game, I am starting to get bored of it. I've never successfully completed a game, and at this point, am not convinced it's "winnable". Perhaps if I ever could finish a game I might feel differently. But boredom has set in so may never find out...
4 stars: Very addicting game but also frustrating! I downloaded this game as I was walking onto my plane as something to 'hopefully' hold my attention for 2.5 hours. Well, it did that and more! I love playing it so much! I wish I started on quick mode because I'm feeling frustrated that I'll never finish ...