Video game distributors are similarly bound by voluntary compliance to check the age of the purchaser against the rating of the game to prevent the sale of mature titles to younger players.

Hex says "occasionally we might give you a glipse of a mature title but only where it's neccesary to make a point", and adds that the contentious content would always be excluded.

"They are tired, mature titles," Mr. Bibb said.

The magazine featured more mature titles, marketed at adults rather than teenage readers.

"They're launching new magazines and their mature titles have had an interesting step up over the past couple of years that Don and Norman have been there."

Cultural differences also allows this rating on more mature titles such as Terminator Salvation, Sora no Otoshimono and The Disappearance of Haruhi Suzumiya.

By the late 1980s DC has published many mature titles such as Hellblazer, Swamp Thing, and Lobo.

A few games use cel-shading today, including more mature titles such as No More Heroes, Borderlands 2, and Crackdown.

"People can get the games easily," he said of the mature titles.

Independent video game developer Derek Yu stated the game is the most mature title which McMillen has developed in terms of design.