Adults Only games are kind of like four-leaf clovers--you know they exist, but you’d have a hard time finding one anywhere. The numbers don’t lie: Since its inception almost 20 years ago, the AO rating has been handed out to less than 30 of the 22,000 games submitted for review to the ESRB. For you non-math folks out there, that’s not many.

How did it come to this? There are plenty of NC-17 movies released, and even more X-rated films--why has this distinction earned such a taboo with gamers? Well, there are various reasons, both commercial and social in nature. But to give you the complete story, we’ll have to take a little trip back in time, wading through all the gore, boobs, lawsuits, and more boobs the AO rating has produced in the process.

We begin our journey in a strange, dirty era known as “the 1980s,” a time when arcade machines and primitive home consoles ruled the gaming landscape. Many may fondly remember these early days as being more wholesome than the murder-infested scene today, but the reality is that things were never that simple.

Just because there was no AO rating at this time doesn’t mean that games meant solely for adults didn’t exist. Titles like Custer’s Revenge (in which you control a naked man sporting an engorged penis and attempt to rape a woman tied to a pole) and the first Leisure Suit Larry (in which the titular protagonist seeks out prostitutes, can contract venereal diseases, and kills himself when you lose) pushed the boundaries of what was acceptable to put in a game, and most certainly would have been slapped with the AO tag today. As gaming’s tech improved, more titles like these popped up, furthering the feeling that there needed to be some sort of system in place to inform customers inform customers of decidedly tasteless content.

Those feelings of need became much more urgent in the early ‘90s, when violent games such as Doom and (especially) Mortal Kombat led some U.S. Senators to hold hearings on the effects of graphic video games. You can imagine how that went--some present said these games were corrupting our society, others said they were training child-killers. Things continued to escalate, and eventually the government introduced the Video Game Rating Act of 1994, which threatened to create a ratings system of its own if game companies didn’t take action.

This forced the industry’s hand. Around this time, Sega came up with its own system (the Videogames Rating Council) to rate its games, other companies like 3DO took similar measures, and Nintendo maintained that everything on its platforms were family-friendly and thus didn’t need to be rated. But the government wasn’t satisfied, and a compromise needed to be formed. After some more squabbling, and after the creation of an industry coalition known as the Interactive Digital Software Association (which later became the Entertainment Software Association), late 1994 finally saw that compromise arrive in the form of the Entertainment Software Rating Board. The ESRB, of course, introduced the Adults Only rating, reserved for games deemed unsuitable for people under the age of 18.

The other major reason AO games are so hard to find these days is because none of the three major console makers want anything to do with them. The Nintendo Buyer’s Guide plainly states that the company “does not sell or license games that carry the ESRB rating ‘AO’,” while Sony has said in the past that “it's SCE's policy not to allow the playback of AO rated content on our systems.” That’s pretty clear cut.

Similarly, when developer ThriXXX proposed to offer “sex simulation software” for Kinect in 2010, Microsoft responded by asserting: "Xbox is a family friendly games and entertainment console and does not allow Adults Only content to be certified for use on its platform, and would not condone this type of game for Kinect." Such statements may or may not be entirely true (Gears of War isn’t exactly cuddly, last time we checked), but they do leave zero wiggle room for any aspiring AO game developer trying to get their product onto consoles. And once again, a lack of platforms equals a lack of income.

So, the industry establishes the AO rating and it was used all the time, right? Wrong. It carries a stigma, as seen soon after the rating’s system was established with Thrill Kill. Initially touted as the next Mortal Kombat, Thrill Kill was an over-the-top 3D fighting game, which featured sexually suggestive, sometimes fetishistic overtones; brutal, Fatality-like kills; and a roster of fighters that included a “gimp,” a dominatrix, a cannibal, and other all-around taboo types. It was soon rated AO by the ESRB. Obviously.

Naturally, the game grew to have its fair share of detractors. Unfortunately for its developers at Paradox Development (aka Midway Los Angeles), Electronic Arts was one of them. After purchasing Thrill Kill’s original publisher, Virgin Interactive, EA cancelled the game only weeks before its release, citing that “the tone and the tenor of the game was just too violent.” Plenty of gamers were incensed, but the precedent was set: Aggressively “adult” games would have to proceed with caution from now on.

Obviously, with so few AO games out there, there are only a handful of companies who have experience creating AO content. One of the more prominent of these select few, however, is Peach Princess, a California-based publisher that specializes in translating Japanese “bishōjo games” into English-language releases. Literally meaning “pretty girl games,” the bishōjo genre doesn’t always consist of adults only material, but it often features sexual content, and it does include the “eroge” subgenre, which Westerners more colloquially refer to as “hentai games.” You get where we’re going with this.

Since its first release in 2001, Peach Princess has put out a multitude of AO-rated games, including such hits as X-Change, Tokimeki Check-in!, Yume Miru Kusuri: A Drug That Makes You Dream, and many others. All of them have only been released for PC, and all of them have been rated AO for “Strong Sexual Content.” (The only other developer to have such a record is MacDaddy Entertainment, which essentially puts out Western-produced porn games). Peach Princess’ head Peter Payne understands that he’s not exactly trafficking in mass-market content, terming his company a “niche within a niche” in a 2006 interview with AMN Anime. It’s hard to disagree with him.

While the vast majority of AO games receive their rating due to strong sexual content or, to a much lesser extent, graphic violence, Peak Entertainment Casinos stands as the only game rated as such for gambling. Yes, gore-less, genital-less, unsimulated gambling, the kind where players could put their real-life cash on the line.

Most titles like this don’t bother submitting their products to the ESRB, but PEC actually wanted the AO rating in order to reinforce its stance against underage gambling. This marked perhaps the only time the AO tag has ever been used as a form of activism, strangely enough.

One less common way certain companies approach the AO rating is to save it for “Extended Cut” editions of their already-released games. Take, for example, Quantic Dream’s Indigo Prophecy (which garnered critical praise). Released in 2005, the North American version of Quantic Dream’s work was forced to neuter the vast majority of its sexual content in order to avoid the AO retail death knell, while other regions’ releases received no such treatment.

The company played by the rules, but soon put out Indigo Prophecy Director’s Cut, a more risk-free AO release that PC fans could purchase if they wanted to get the “complete” version of the game. It’s not perfect, but it’s a model that allows one’s artistic vision to not be completely compromised. Leisure Suit Larry: Magna Cum Laude (which was pretty…not good) went through a similar process a year earlier with its Uncut and Uncensored! edition, but we don’t have to talk about that sleazeball here.

By far the most infamous of all AO-related incidents is the uproar over 2005’s “Hot Coffee” mod for Grand Theft Auto: San Andreas. For the four people reading that don’t know what we’re referencing, “Hot Coffee” was the term given to an initially inaccessible minigame within San Andreas that, when unlocked (via third party hacks or downloaded software), let protagonist Carl “C.J.” Johnson have sex with any of his in-game girlfriends. She’ll invite C.J. in for “coffee,” and they’ll do the nasty (completely clothed, by the way) in some of the most awkwardly-animated sequences put to code. Seriously, go look it up.

Select activists and politicians promptly went bananas. Several class-action lawsuits were fired at publisher Take-Two. Noted anti-game activist (and now disbarred attorney) Jack Thompson made plenty of noise, even calling ESA president Doug Lowenstein a “thug” at one point (alongside the above title quote). Senators Hilary Clinton, Joe Lieberman, and Evan Bayh eventually sponsored the Family Entertainment Protection Act in 2005, which, among other things, would’ve put harsher restrictions on businesses that sold M- or AO-rated games to minors, and would’ve led to an federally mandated annual inspection of the ESRB’s ratings. While that bill didn’t make it into law, San Andreas’ rating was soon changed from M to AO, forcing developer Rockstar to go back and produce “Coffee”-free versions of the game so that it could still be sold at major retailers. The kerfuffle eventually died down, but the chaos that one little mod created would not be forgotten.

Why not just make the game AO and sell it in stores? Well, because companies actually can’t. Perhaps the most crucial reason behind the lack of AO games is because the rating simply can’t get the bills paid. This isn’t necessarily always the game’s fault--virtually all major retailers refuse to sell AO products, effectively making the rating a commercial death sentence.

“We simply don’t carry AO games at all,” an executive from retail giant GameStop told 1Upa few years back. “It’s company policy.” They’re not the only ones. Wal-Mart, Target, Best Buy, GameFly, and virtually any other big chain you’ve heard of has done the same. With smaller, local game shops dying out, the only place many players have to nab an AO game today is in some corner of the internet. And if you can’t sell your game anywhere, it’s sort of hard to make much of a profit from it.

Eurogamer’s review of Lula 3D, a 2006 AO adventure game best known for touting its “Bouncin’ Boobs Technology.” You play as a porn star that has to rescue her kidnapped pals, who are also porn stars. Along the way, you’ll have sex, flash people, have sex, and have more sex. You’ll also be playing a terrible game.

Lula 3D is one of the better examples of why there’s such a collective stigma around Adults Only games: Many of them just aren’t that “adult” in the first place. Lula itself is part of a series that includes such titles as Lula: The Sexy Empire and Wet Attack: The Empire Cums Back. From Riana Rouge to Singles: Flirt Up Your Life, all too often AO games seem to focus less on, y’know, being good, and more on shoving boobs in your face. The half-hearted attempts at humor or maturity almost always fall flat, and what you’re usually left with is a broken game and some personal embarrassment. It’s a shame, truly, because most adults deserve better.

As the “Hot Coffee” incident showed us, Rockstar is certainly no stranger to Adults Only-controversy. Only two years after the San Andreas hubbub, the UK dev found itself in hot water again with 2007’s gruesomely violent Manhunt 2. The second installment in the action horror series was initially slapped with the AO rating, marking one of the few times (like the aforementioned Thrill Kill) that a product received the label purely for violence.

Since Manhunt 2 didn’t involve digital naughty time, the uproar surrounding it was slightly more muted than usual, but still fairly sizable. Publisher Take-Two clashed with the ESRB again, saying things like “we believe the process of rating videogames is to help people make informed entertainment choices and not to limit them” (via the Escapist), and all that jazz. In the end, it didn’t matter. Rockstar went back and censored the console versions of the game in order to avoid the usual AO trappings and have their game released on the console, the PC version kept the AO rating, and the typical “anti-AO” stance found in virtually all aspects of the industry could not be budged. The judgment was harsh enough that it even made some companies, like Condemned and F.E.A.R. dev Monolith, feel pressured into removing potentially questionable content from their own games.

One of the most frequently asked questions about AO games has to be just what makes its content so different from the scores of violence, sex, and the like already found in their M-rated counterparts. After all, there’s only a one year difference between the age required to buy a Mature game (17) and an Adults Only one (18). And if retailers, console makers, and publishers are so averse to the few branded AO, why even have a separation in the first place?

According to ESRB president Patricia Vance, the real usefulness comes in “communicating intensity.” “It indicates that the content in the game is more intense than what is typically found in an M-rated title,” Vance told Kotaku around the time of the Manhunt 2 controversy, “and the rating is there because that distinction is useful to consumers.” She’s frequently compared the M-to-AO relationship to the movie industry’s R-to-NC-17 difference as well, and while such responses don’t exactly solve the fact that AO games are effectively dead on arrival, it gives at least some insight on a topic that’s been swept under the rug over the years.

The landmark Supreme Court ruling in the case of Brown vs. Entertainment Merchants Association marked yet one more legal victory for the gaming industry in its seemingly eternal struggle with local and federal governments over Mature and AO content. On the surface, it revoked a California state law enacted in 2005--right around the time of the “Hot Coffee” fiasco--that prohibited the sale or rental of loosely-defined “violent video games” to minors without parental supervision. The bill would have also required “violent” games to bear a two-inch-by-two-inch sticker on their front covers labeling them as such.

Perhaps more importantly to gamers, the ruling saw the Supreme Court declare, in a 7-2 decision, that video games were subject to full First Amendment protection. In his majority opinion, Justice Antonin Scalia stated that depictions of violence in media have never been subject to government regulation, that there was no definitive link between violent games and youth, and that no government could claim “a free-floating power to restrict the ideas to which children may be exposed,” be they games or not. Video games, it was believed, were to have the same rights and expressive value as books, television, or film. Obviously, many gamers and game companies lauded the decision. It wasn’t a complete “Get Out of Jail Free” card, but it was a big step forward for the industry at large.

We’ll complete our bloody, squishy trip through AO’s history with some hope for the future. In an interview with Gamasutra earlier this year, ESRB president Patricia Vance said that, as games as a whole shift from physical stores to digital ones, it may be “very possible that there will be greater acceptance of an AO rating going forward.”

“And by the way, I think that would be a good thing for the system,” Vance continued. “It's very frustrating that publishers can't release AO product, in many cases.” So long as future AO games treat their consumers like adults (and not pent-up hornballs), it’s hard to find fault in her statements. The powers that be will always have one eye focused squarely on video games, it seems, but it’s certainly encouraging to hear that there may yet be light at the end of this dark, messy AO tunnel.

The future of AO games might be unknown, but as the medium evolves so will the ratings that govern them. Maybe, in the future, game publishers and developers will be more open about creating games that garner the rating. Otherwise, well, we'll just have to settle for brief nudity and hyper-violence, instead of sex and super-hyper-violence.

And if you want more ESRB-related news, check out gaming's most violent duos and instances of Nintendo's censorship of Japanese games in America.