5 stars: Very enjoyable. Thus app allows you to record guesses so you can keep track of user progress.
5 stars: Love it and now most of the ads are short.
3 stars: I prefer ad-free apps and am willing to pay. There is no purchase option. The reset button is also too easy to accidently hit. I constantly hit it by mistake. There is no check option when you hit reset. It wipes out everything you've done instantly. It's sort like a mean prank. I like hard puzzles and found the one puzzle I played sufficiently challenging. The flashing ads on the bottom of the screen are distracting and annoying.
3 stars: It's hard to get to the game. There are lots of interruptions.
2 stars: Defective ads killed the app. I have uninstalled and reinstalled this game a couple times but as soon as I would tap on a skill level to start a game, I get a black screen instead of an ad. There's no way to get back to the game without closing and reopening it, only to have it happen again. I played this for a couple months with no issues but now I've uninstalled it for the last time and am moving on to a different version altogether.
2 stars: Doesn't work properly most of the time. You'll fill in most squares and then realize there's a mistake (that the app doesn't tell you about!) Then you have no idea where you went wrong to fix it. There's a 'check your mistakes' box but every time I'd press it, it would say 'no mistakes found' but there would be a box with two of the same numbers.