Tokyo, Japan – Maki Kaji, known as the "Godfather of Sudoku," died at his home in Tokyo on August 10 at the age of 69.

Kaji, known for making mainstream one of the world's most beloved number games, has passed away from bile duct cancer, the New York Times reported. The sad news was announced on Tuesday by Nikoli, the puzzle company he co-founded.

The puzzle maker is best known for popularizing Sudoku. In a 2008 speech, he explained that he "fell in love" with a game called Number Place in 1984, which he wanted to incorporate into his Nikoli company.

But Kaji didn't like the game's original name and was determined to find a Japanese one, settling on Sudoku, an acronym whose long form translates roughly to "Numbers should be SINGLE, UNMARRIED."

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"I wanted to go to horse racing that day, so I created the name in about 25 seconds," he explained. He also joked that he was happily married and did not devise the name because he "wanted to be single again."

Kaji dropped out of university, but that apparently didn't dampen his mental prowess. He and his team created thousands of human-generated Sudoku puzzles during his lifetime.

He seemed very happy, despite not trademarking Sudoku: "I did not become a millionaire, but I'm glad Sudoku is now loved by billions of people. I enjoy my staff saying they are proud of their job, I enjoy a glass of wine with my wife every night, and I enjoy horse racing every weekend. I am very much satisfied with the way I am."

He is survived by his wife Naomi and two daughters.

Many puzzle lovers around the world are grateful to Kaji for bringing the joy of Sudoku to their lives.