His Japanese company announced Tuesday that Maki Kaji, who was the creator of Sudoku, a popular number puzzle, has passed away. He was 69 years old and had bile-duct cancer.

Kaji, also known as the “Godfather” of Sudoku, created the puzzle to make it easy for children and those who don’t like to think too hard. It’s named after the Japanese characters for “number”, and “single,” where players place the numbers 1-9 in rows, columns, and blocks. They don’t have to repeat them.

Ironically, Sudoku didn’t become a worldwide hit until 2004 after a New Zealand fan pitched it to The Times and got it published. Japan discovered its own puzzle two years later as a “gyakuyunyu,” which is a “reimport”.

Kaji, who was the chief executive of his puzzle company Nikoli Co. until July, died at his home in Mitaka in the Tokyo metropolitan area.

Maki has traveled to over 30 countries in order to spread his love of puzzles. According to Nikoli, a Tokyo-based company that makes Sudoku puzzles, Sudoku championships have attracted more than 200 million people from 100 countries.

Nikoli stated that Sudoku was not trademarked outside of Japan. This drove its popularity overseas.

“Kaji-san invented the name Sudoku, and was beloved by puzzle lovers from all over the globe,” the company said. The company released a statement saying that they are deeply grateful for your support throughout the life of Kishi-san.

Originally, Sudoku was called “Suji-wa-Dokushin-ni-Kagiru,” which translates to, “Numbers should be single, a bachelor.” In recent years, Sudoku, believed to be the world’s most popular pencil puzzle, has come out in digital versions.

Maki was born on the northern island of Hokkaido and founded Japan’s first puzzle magazine. He dropped out of Keio University, Tokyo. In 1983, he founded Nikoli and around the same time created Sudoku.

Yoshinao, the Nikoli chief executive who succeeded Kaji, stated that Kaji was easy to get along with and had a “unique, playful approach to life”.

Anpuku stated that “our mission is to pursue Maki’s vision and potentials.”

Nikoli has supplied original puzzles for more than 100 media companies (10 of which are foreign).

Mainichi, a major Japanese newspaper, credited Kaji with starting puzzle sections in bookstores and also for introducing “Sudoku” into the Oxford English Dictionary.

Naomi, Kaji’s wife, and their two daughters are his survivors. A funeral service was held for close relatives. Nikoli is currently arranging a separate memorial service, but the details are still unknown.