Level 3 sudoku puzzles on this website can be solved using advanced techniques, such as X-wing, XY-wing, XYZ-wing, swordfish, and jellyfish, plus the techniques in level 1 and 2. No divide-and-conquer (try-and-error) is needed.

This page is especially for X-wing pattern only. For training with other patterns, check the links below.

Daily sudoku (XY-wing training).

Daily sudoku (XYZ-wing training).

Daily sudoku (swordfish training).

Daily sudoku (jellyfish training).

Principles of X-wing:

Given two parallel and two perpendicular links, there are four intersection squares. Suppose, in the two parallel links, a number can only appear in the intersecton squares. Then, in the two perpendicular links, the number can only appear in the intersection squares as well. That is, this number cannot be in any other squares in the two perpendicular links.