For the price, it is a pretty good game. The GUI is clean, and the highlighting feature makes it very easy to see patterns for a particular number. It is also easy to add and remove pencil marks. The Auto feature only shows you the available numbers for a particular cell, but does not fill in the the pencil marks like other versions do. This could be a plus or a minus depending on your preferences. On the down side, the pencil marks are a bit small, although they are positioned in the cell so that you dont really need to read the number to know what it is. A timer would be handy so that you could see how fast you are going. The biggest problem with this game, however, is that there are often multiple solutions to any particular game. Youll often be in a situation where there is no obvious answer, and will have to guess at a number. Ive found that my guesses are always right, and that theres always two or four open cells at the very end with identical pencil marks. This mars an otherwise fine game.