Have you ever tried other variations of the game?
They have 16x16 puzzles, letters/symbols puzzles, word search puzzles, and math puzzles. Yes, I'm referring to all variations of Sudoku.
16x16 is pretty much like 9x9. Instead of 3x3 grids, it's 4x4 grids with numbers going from 1 to 16.
Letters/Symbols is like the regular puzzles except letters/symbols are used instead of numbers.
Word search is like the numbers version, but the person has to solve the puzzles in letters format and then find the mystery word at the end.
The math puzzles are something new. Instead of the grid being partially filled in with some numbers, the whole puzzle is blank. However, some of the boxes are connected with smaller boxes and a number inside that represents the sum of all the enclosed boxes.
You can find these at your local grocery store or Wal-Mart.