September 9 is International Sudoku Day. Can you guess why?

A quick look at nine interesting tidbits about the world of Sudoku:

1. Sudoku is part of a field called ‘recreational mathematics’. But you don’t actually need any math to play it. As a logic game, sudoku works the same if you replace all the numbers in the puzzle with letters or symbols. Would you try one that uses symbols from The Matrix’s famous digital rain?

The Matrix’s famous green code (which, by the way, was inspired by a book of sushi recipes) could easily be used to create sudoku: an example of how flexible the game really is. Image: github.com

2. The World Puzzle Federation (yes, that’s a real body) designated September 9 as International Sudoku Day since the date forms a 9×9 pattern — the same size as a classic Sudoku grid!

3. India’s best Sudoku player is Rohan Rao, who has won nine editions of the Indian Sudoku Championship. The top players from this contest represent our country at the World Sudoku Championship, which will begin in Poland this winter. Have you met our 2022 national team?

4. A Sudoku grid’s difficulty depends on how many starting numbers are provided, and where they’re placed. Also, a grid can have more than one solution.

5. ‘Sudoku’ is a shortened version of the Japanese suuji wa dokushin ni kagiru (‘the numbers must remain single’). The name is a registered trademark in Japan, held by the puzzle company Nikoli. Its late president, Maki Kaji, is widely regarded as the father of modern Sudoku, having popularised the game since the 1980s.

6. Sudoku grew to such global popularity after Kaji’s efforts, especially in the West, that in 2010 it officially became the most common puzzle game on the Nintendo DS.

7. The Guinness World Record for the fastest solve of a ‘Very Easy’ level Sudoku is held by American player Thomas Snyder. He completed the puzzle in a blazing 1 minute and 23.93 seconds!

A glimpse of the World Sudoku Championship, where top players like Snyder battle it out every year. Image: Спасимир/Wikimedia Commons

8. India’s earliest known version of Sudoku is a magic square (a grid where the numbers on each side add up the same amount) that dates back to roughly the 1st or 2nd century AD. Created by the philosopher Nagarjuna, it was found in a text called the Kaksaputa, and was a 4×4 number grid.

9. Most Sudoku published in newspapers or free websites are computer-generated. However, there exist several puzzle constructors who make custom Sudoku grids by hand. It’s a niche but passionate community, and you can find their creations on YouTube, puzzle blogs, or by joining groups like Logic Masters India. These puzzles are part of the wide world of Sudoku variants.

For more trivia about the world of puzzles, follow @iepuzzles on Instagram!