Gaming service Steam has changed its content policy to allow publishers to add anything to its store — but with some exceptions.

Valve Corporation, the parent company of the games distributor, said in a blog post Wednesday that it would "allow everything" on the Steam Store, apart from games that it described as "illegal, or straight up trolling."

The firm said its decision meant users would see things that they "hate, and don't think should exist."

"Unless you don't have any opinions, that's guaranteed to happen," Valve said. "But you're also going to see something on the Store that you believe should be there, and some other people will hate it and want it not to exist."

Steam's policy change follows the platform's banning of a controversial game called "Active Shooter," designed to let players simulate a school shooting. The game sparked a backlash amid a number of recent school shootings in the U.S.

The game is not the first school shooting simulator. Another, called "Super Columbine Massacre RPG!" was released in 2005 to let players act out the 1999 Columbine High School shooting.

And it is not the first instance of violence in video games that has led to criticism. Rockstar's highly successful title "Grand Theft Auto V," and many other games made by the developer, have caused outrage from some critics due to worries that violence in video games could reflect violence in real life. However, research has suggested that there is no evidence to link the two.

"Active Shooter," which was due to be released on Wednesday, was not mentioned by Valve in the announcement. But the company has not backtracked from its ban on the game, despite seeming to take a more open approach to what it allows.

The firm said it would press game developers to disclose any potentially "problematic" content during the submission process to help it comply with laws around the world.

PC gaming is a multi-billion dollar industry. The industry was forecast to generate $29.4 billion in 2017, according to data compiled by market research firm Newzoo.