Good user interface, varying difficulty

O used to have a Palm and enjoyed the Sudoku app there.
After switching to an iPhone I picked this app after reading many review.
I play Sudoku to kill time and always play on the highest level of difficulty.
I usually dont care how long it takes to solve a puzzle. Sooner or later they all get cracked. I never do try and error but only apply strict reasoning.

What I noticed about this app is that it has a very nice and useful interface.
I make a lot of use of the "fill in" function that shows me all possible numbers for a field based on the simple exclusion rule.
I then apply the higher level rules to eliminate more numbers until the puzzle is solved.

The one thing that strikes me as odd about this app is the variation in difficulty of the puzzles. It is huge!
At the highest level, I still get almost trivial problems. But also extremely hard ones to crack.
Tonight I actually had an insolvable one!!

I give it z 4 star rating for entertainment value and quality of user interface.

Zappa124 about Sudoku Unlimited