Opdoku = Calcudoku + Mathdoku

M.: »Absolutely love this app - simple easy to use interface and free.« D.: »There's no advertising, they don't ask you for money, and the puzzles are great.« Opdoku is completely free of charge, with no adverts or additional purchases. Sounds good? Try it out today! The rules are simple: ○ As in Sudoku, each digit can only appear once in each row and column. ○ Each digit is part of a group…