@asuffield said:
Sudoku is the realm of the mentally limited. It's really really easy when you know how to do it (just mechanically and mindlessly apply half a dozen rules) and you can write a program to solve them in under half an hour. They're about as challenging as a join-the-dots "puzzle".
Actually, solving sudoku puzzles is known to be NP-complete. It's just that standard 9x9 grids of 3x3 blocks are so small that they can easily be solved by computers in under a second. Try writing a generalized solution for any size...