We just release three new themed variants of Sudoku apps for Android. Each app features 1000 normal difficulty puzzles and 500 hard difficulty puzzles. The three apps are:
Sudoku - Batman Fan Art Edition
https://play.google.com/store/apps/details?id=com.dd.sudoku.batman.free
Sudoku - Angry Birds Edition
https://play.google.com/store/apps/details?id=com.dd.sudoku.ab.free
Sudoku - Cat Edition
https://play.google.com/store/apps/details?id=com.dd.sudoku.cat
Please check them out and let me know what you think!