By Chris Hogg
BBC News, Tokyo
In Japan's rapidly ageing society, more and more older people are looking for ways to keep them active and alert for longer.
Games like Nintendo's Brain Training: have sold well in Japan
Electronic games makers have responded with new products designed to train your brain.
The games developed by scientists will, it is claimed, help to delay the onset of dementia.
Millions have been sold so far in Japan. This month the games will be launched in Europe.
In a Tokyo classroom, a teacher demonstrates how to turn on the Nintendo DS and plug in the disc with the game on it.
This is step-by-step stuff. It has to be. No-one in the room is under 40. Most of them are much older and they have not handled games like this before.
The teacher who came to this himself quite late on is Atsuo Umetsu. He is showing his pupils how to play a game that tests your mathematics ability.
After a few minutes of gentle encouragement, they start to get the hang of it as most of the grey gamers are grinning.
This is brain training. They are using special software designed to stimulate the grey matter and keep the fingers nimble. It is a craze that has Japan hooked.
"It's not difficult to learn how to play them," said the teacher, Mr Umetsu. "After all I learnt, so everyone can do it.
"It's good for the brain and we are using our fingers. It's keeping our bodies active."
The game they are playing has been developed by scientists who claim it can help to delay the onset of dementia.
In this version the player has to solve simple sums as quickly as possible. But there are many different types of game on the market.
After the maths game the students try a golf game that tests hand eye co-ordination. They are pretty enthusiastic.
Sudoku games are also seen as providing a brain workout
"I'd never seen these kind of computers or games before," said Shikoko Koyama.
"I saw an advertisement about this class and I thought I'd give it a try. But I don't really get it," she added with a grin.
Sitting next to her is Emiko Kuramochi, who earlier had let out a squeal of delight when she scored top marks in the mathematics game.
"I wanted to try this popular brain training game for myself," she said. "My sons can play these games but I can't and I want to challenge them."
Dr Takao Suzuki, an expert in the care of older people, believes Japan is pre-occupied by old age.
However slim the chances that this software really works, who would want to be left out?
"There are a very limited number of scientific reports to prevent the dementia by doing such games," he said.
Games are not just for a younger generation
"But in an aged society like Japan and the UK, nobody wants to get dementia so even if there is a very small possibility that it might work, most elderly people will want to do something in order to prevent dementia."
It is not just small portable machines that can make a difference.
At a Tokyo day-care centre for the elderly and infirm, two old ladies are practising drumming in time to the music on the type of huge electronic game you see teenagers huddled around in amusement arcades.
They bash away in front of the flashing lights as the golden oldies blast out from the speakers on either side.
Next to them one of their friends is thumping crocodiles that pop up in front of her with a rubber hammer.
Nearby another lady is trying to operate a small crane to try to win some sweets.
The idea behind this is to entertain a new generation while keeping them healthy and active. This facility is run by the video game company Namco.
"With our low birth rate," said Namco spokesman Yoshiaki Kawamura.
"It's obvious we're going to be dominated by people over the age of 60 from now on. They want to have fun in their lives.
"The computer game industry for the elderly is a growing market for us."
No one has proved yet beyond any doubt that playing the games your children or grandchildren are addicted to will keep your brain working well for longer.
But most scientists agree it cannot do any harm, to learn a new skill, keep your joints active and of course to share.