How to solve Sudoku

　　 　　 　

Date	Contents
2020/10/26	(13) What is xy chain.
2020/8/22	(12) What is xy chain link.
2020/8/3	(11) What is xy wing.Three kinds of xy wings.
2020/4/22	(10) What is Finned jellyfish.
2020/4/2	(9) What is Finned swordfish.
2020/3/31	(8) What is Finned fish.
2020/3/22	(7) What is xy-wing part 2.
2020/2/7	(6) What is xy wing. And what is Remote Pairs.
2020/2/1	(5) What is xy-wing.
2020/1/18	(4) What is Remote Pairs.
2019/10/31	(3) What is broken x wing.
2019/10/10(level max?)	(2) What is Swordfish. And what is Jellyfish.
2019/10/10(level max?)	(1) What is x wing. And what is two kinds of Swordfish.