Critical: each ring can spin. By my calculations, there are 64 permutations of arranging just the rings. Fortunately, if there is a conflict, it's highlighted in red.
I've tackled about 20 of the easy levels.
Numerous times: I've rotated the rings, then started filling in the grid, only to discover that my rings were wrong. Back to square one. Still, I wonder if there are multiple solutions in terms of ring rotation.
In a regular sudoku grid, every single square must be one and only a distinct number. That's not the case with Sudoku Spin. If a sector is missing only a 3 and a 7, and they both land on the same ring, then the order is not important.
The graphics are very good.
Other Innovative Sudoku Puzzle Apps
Kropk'i Sudoku This is really a Latin Square with a couple of innovative ideas. It plays fast.
Quindoku Same as Logi5Puzz
Logi5Puzz Same as NumDom. But NumDom has larger grid sizes.
Spindoku is totally different, but still very cool.
Hi-Lo Sudoku is one of my favorite variations.
Cryptdoku I played it so long ago, but it's cool. Long gone from the App Store.
Stimko Gold - outstanding version of squiggly Sudoku. Handcrafted puzzles.
Kakooma - interesting for about 3 levels
RollDoku - never even solved 1 level, so hard
Cohabit- played this on my ipod touch - before ipad was invented
FlowDoKu - one of my favorites. Will not delete this.
Sudoku Mine combines Sudoku with Minesweeper
Sudoku Killer combines Sudoku with Kakuro. I've spent a lot of time on this one. I can do the easy levels in about 10 minutes.
3Doku - a cubic version of Sudoku
Pokergreen Puzzles - a poker version of Sudoku