A Bulgarian created the most difficult Sudoku in the world.

The manager of the Bulgarian castle in Ravadinovo Yanko Krastev improved the record from 2012 of the Finnish mathematician Arto Inkala. The difficulty of this interesting mathematical puzzle is rated on a scale of 1 to 5, with the Finn’s achievement having the extreme score of 11, but he himself proves in his mathematical justification that it can be improved. This still happened after a 13-year break, and fortunately for us in Bulgaria.
Yanko Krastev is a graduate of the Mathematical High School in Varna, one of the first members of MENSA Bulgaria, a participant in several Mind Games Olympiads. In 2011, on his initiative, the first National Championship of the World Othello Federation was held in Bulgaria at the Castle “In Love with the Wind” in Ravadinovo. In 2023, he also received the prestigious award for “Most Successful Manager” during the World EXPO in Dubai.
“Sometimes the roundabout ways to the top are shorter,” the author of the new mathematical Everest told us and added: “It is a credit to Arto Inkala that he very accurately described where the chances of improving his result are. I used the mathematical method Backtracking Algorithm and from there “fed the data” to create PYTON computer code to the artificial intelligence, which had previously already raised the white flag and told me that it could not cope. I will share the gentlemanly behavior of my Finnish colleague and state that there is a mathematical possibility of improving this record as well, and I hope that this will not take another 13 years.

In addition, I have an exact recipe for where and how you can get creative inspiration and a “Sign from above”: this is the beloved of all Bulgarians Castle “In Love with the Wind” in the village of Ravadinovo near Sozopol. There are hundreds of examples of people of art, science and sports, who, inspired by the miracle of the construction of the castle, believed in their own strength and went far”.

Check out the new Sudoku challenge and test your strength. The possible options are not that many, but only: 6 670 000 000 000 000 000 000.