Ryuta Kawashima, the scientist behind the smash-hit "brain training" games on Nintendo DS portable consoles, turned down the chance to become a millionaire, saying he'd rather work for a living.
The self-confessed workaholic -- who says he has no time for games, even his own -- is instead busy at his job, trying to come up with new inventions aimed at Japan's growing elderly population.
"Not a single yen has gone in my pocket," said the soft-spoken 48-year-old professor with round-rim glasses.
"Everyone in my family is mad at me but I tell them that if they want money, go out and earn it."
His brain-training software, which incorporates quizzes and other simple mental stimulation, is credited with introducing a new demographic to video-game machines as older people try to prevent senility.
Royalties from the brain training software for the Nintendo DS alone have reached 2.4 billion yen (22 million dollars), with 17 million titles sold worldwide since its debut in Japan in May 2005.
Under the rules of his employer, state-funded Tohoku University, Kawashima could take up to half the proceeds with the rest going to the school.
But Kawashima, married to a high-school classmate with four sons, is happy to live on his annual salary of around 11 million yen (100,000 dollars).
"To hear this may put you off -- but my hobby is work," he told AFP in an interview at his office in the northern city of Sendai.
Asked whether he ever thought of taking the royalty money and moving to a tropical island, Kawashima simply said: "I wouldn't know what to do there. If I had such time to spare, I want to do my research."
Indeed, it seems like nothing gets in the way of work. When for instance he decided last year to lose 20 kilogrammes (44 pounds), he just cut down on food, he says, adding: "If there is time for physical exercise, I want to use it for research."
Kawashima became interested in brains when he was a teenager, saying that he "wanted to put my brain in a computer so it would be around to see the last day of humanity".
While that ambition may still be a long way off, Kawashima pours his portion of the royalties from his work into funding research. He has built a 300-million-yen laboratory at the university's Institute of Development, Aging and Cancer where he works, and another lab worth 400 million yen is due to be completed in March.
Kawashima has received public praise for his apparent philanthropy, but says other researchers have the right to earn money from their work if that is what motivates them.
People can train their brains just as they do their bodies, Kawashima says.
He no longer uses his own software to keep his own brain nimble, he says, confident that his research work is enough.
Now in the fourth year of an education ministry-funded project looking at youngsters' brain development, he says he does not yet know how children's minds are affected by long hours playing video-games.
Despite developing software for Nintendo, Kawashima banned his four sons, now aged 14 to 22, from playing video-games on weekdays, with only one hour allowed at weekends, and once destroyed a disc when they broke the rules.
"What is scary about games is that you can kill as many hours as you want. I don't think playing games is bad in itself but it makes children unable to do what they should do such as study and communication with the family," he says.
The professor believes in strict discipline for young children and disagrees with the notion of making study fun.
"Having fun is not studying. Making them study is not to entertain children but to pressure them to make efforts. People fall to lower and lower places unless they are driven to go higher," he said.
In his latest research, a team led by Kawashima is joining forces with Toyota Motor Corp to develop a car to keep elderly drivers alert and mentally fit to prevent accidents.
As for growing old himself, Kawashima is also sure about one thing -- "I'm confident I'll go senile.
"Researchers, especially those in medical fields, are said to die of what they are studying. Since I've been studying the brain, I'll die of a brain disease," he said with a grin.