Joseph Abell

Sudoku Difficulty Definitions

No complex deduction needed. You should be able to solve puzzles by searching for cells where only one number can go. The most complex it should get is to ask you to recognise a pair of numbers are locked into a grid, so other numbers cannot go in those cells.
Knowledge of some advanced topics is required. Examples of these are, x-wing, y-wing, and swordfish techniques. You shouldn't need to use these techniques more than 2-3 times to solve a puzzle.