Sex. Such a small word for such a huge aspect of the human experience. If you're a 12 year-old boy, you're giggling. If you're an adult your attention is wandering ... come back! There you go. And if you're a developer or publisher, you're breaking out into a sweat. Why? Because games just can't do sex.
Correction - games won't do sex. Technically it's possible to show entwined bodies, regardless of the technical difficulties of making the result look like anything other than a pair of inflatable dates being sucked through a tiny airlock. In practice, though, games and their creators seem nonplussed, even frightened by it.
Games aren't the first medium to hit this barrier. It took Hollywood decades to show on-screen intimacy, and in some ways it remains oddly prudish. So maybe people just don't want to see sex?
Famously - during the classic Hollywood period of the 40s and 50s - there were rules governing how long kisses could last, while 'sex scenes' were little more than bedroom doors swinging shut, slow fades to roaring fires, bursting fireworks, trains going into tunnels and rockets taking off.
The world of publishing encountered similar hostility, with novels such as DH Lawrence's Lady Chatterley's Lover suffering all kinds of problems. First published in Italy in 1928, it wasn't deemed acceptable for UK brains until 1960 - after it had passed the Obscene Publications act of 1959.
Between those years, however, illegal translations became highly prized. Hey, perhaps people do want to see sex, after all. These days, America spends $3 billion a year on porn - more than Africa spends on education. Incredible. Don't they know about the free stuff on the internet?
US films and TV have relaxed their approach to sexual censorship, and big-budget shows such as Game Of Thrones, Rome and True Blood are happy to offer graphic snapshots of both sex and violence. What's more, they make little distinction between the two in terms of what's acceptable.
Games, however, are only half-way there. While games are happy to offer detailed ultra-violence, they keep a very detached stance on the intimate stuff.
Take God Of War 3, for example. Fresh from (literally) ripping men in half, gouging out eyes and ripping off heads, Kratos stumbles upon the Goddess of Love, Aphrodite, in her bed chamber. She's topless, writhing around with a couple of slave girls like a teenage boy's dream, but with chaste little pants on. Seeing Kratos, she tempts him into bed and... the camera pans to the giggling slaves.
Next thing you're tapping out Quick Time prompts to the sound of comedy groans and a few seconds later (The Ghost of Sparta's never had this before, it must be the stress, he's so sorry...) the camera pans back to Kratos, fully dressed and ready for more wholesome blood and murder. Basically, penetration's only OK when the sword isn't pork, and one person is dying.
Anything wrong here? This isn't a healthy message, and nor is it grown up. Some applauded God of War for even featuring nudity at all - many titles won't go that far - but with zero emotional context it's nothing more than titillation. And do they really think a pair of virtual tits are going to turn us on? Soft(ware) porn, anyone?
OK, God Of War is an action game. It doesn't live or die by the complexities of Kratos' character or his emotional journey. It's about pressing Square to stab. So let's look at more story-driven games, such as Mass Effect 2 and Dragon Age. BioWare, the Canadian developers of both, take a healthier approach to human relationships but - again - shy away from sex.