Each triangle must have 1-9. Each row, continuous or interrupted by the center, must also have 1-9.
There are 10 free levels. I've done 3 of them, including one of the extreme levels. See image.
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.
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
Sudoku Mine combines Sudoku with Minesweeper
Sudoku Killer combines Sudoku with Kakuro. I've spent a lot of time on this one.
3Doku - a cubic version of Sudoku
Pokergreen Puzzles - a poker version of Sudoku