A mock computer game is the latest weapon in the Metropolitan Police's fight against knife crime.
DVDs are being distributed to thousands of teenagers
A DVD of computer generated images and real life footage showing the effects of using knives is being distributed to thousands of teenagers across London.
The campaign's slogan is "Carrying a knife, it's not a game" and the fake game demo is called Knife City.
An interview with the parents of Luke Walmsley, who was murdered at his school, is also on the DVD.
The DVD's main character starts off as an animated image who carries a knife for protection.
When he is involved in a confrontation he uses his knife and as the consequences become apparent he changes into a real person.
The campaign is also using radio advertising, a website and e-mails.
Commander Alf Hitchcock who is in charge of Operation Blunt - the Met's anti-knife strategy - said the DVDs were an "innovative" way of getting the message to young people.
He said: "It allows us to get our important message into the living rooms of thousands of teenagers.
"We hope that this novel approach will help convey the harsh realities of carrying a knife."