You love sudoku, you're enjoying a lot of fun but you have the impression of running in circles, always doing the same actions and take a lot of time to solve a grid? In this case, it's time to get into serious things and learn how to improve your execution and attention time to solve difficult grids.
The X-Wing Technique
The X-Wing technique is to look for four aligned cells that form an X, and that have the same candidate that does not appear anywhere else in the same row or column. This common candidate is called the fish figure.
The swordfish technique
The swordfish technique follows the same principle as the x wing, with the twist of having three basic sets rather than two.
The XY wing or Y wing technique
The XY wing technique is a technique that is often compared to the hooks of an eagle and its prey. The objective is to find the hook cells and proceed to eliminate the prey.