You may not realize it, but you're already playing "the game.''

Oops -- you lose.

Confused? It's actually a pretty simple idea, once you get the hang of it. But be warned, once you join hundreds of thousands of people around the world trying to outsmart and out-think each other, there's no going back.

There are three rules to the game:

1. Everyone in the world is playing it, whether they know it or not.

2. If you think about it, you lose. That counts desperately trying not to think about it, or being tipped off by anyone else talking about it.

3. When you lose, you have to announce it. It can be out loud, on the Internet, or through a note passed in class to soon-to-be angry friends.

"You then have three seconds to forget the game and then you can be reminded and lose again,'' explains Allison Thomas, a Grade 12 student in Cole Harbour, N.S., in an e-mail. Other people allow up to half an hour to forget about the game.

"It's a fun idea, but can be trouble in places like class where a teacher does not play or even a class when your teacher is the one to make you lose.''

Thomas is one of almost 38,000 people -- mostly high school and university students -- who are part of a Facebook group devoted to the game.

Henry Zakay, a Grade 11 student in Montreal, says the game has become popular in an age of supercharged special-effects and entire video-game universes by being so simple.

"Even though it's extremely low-tech, and there's no superpowers you use, or weapons or whatever the scenario is, you're using your actual body,'' says the 17-year-old, who has been actively playing for four years.

"We play video games because we want to try to impersonate what's happening. In the game, you're actually doing it yourself, you're making others lose.''

The game's origins are hazy. The biggest site on the topic, www.losethegame.com, says it's very hard to track since it mainly spreads by word of mouth and has such a common name. That site traces the earliest known Internet reference of the game to August 2002.

"Many, many people e-mail me about how their friend created the game,'' says Jonty Haywood, who first heard about the game in 2001 in Cornwall, England, and started the website in 2005. He says over 300,000 new people have visited the site since then.

Haywood says he's only found substantial evidence for one theory, that the game was created by Jamie Miller from London.

"He says he created the game in 1996 with the purpose of annoying people,'' Haywood, 25, writes in an e-mail from Shanghai, where he's travelling.

Zakay tells the story of writing a math exam in complete silence and coming upon a question about basketball. The game popped into his head, and he announced out loud that he had lost. Five others followed, and the class began to laugh, bewildering the teacher watching over the test.

"It's interactive with everyone, you can have a whole chain of people losing at once,'' he says. "It's fun to see, everyone likes to see a little bit of unhappiness in everyone else, I guess.''

The game also sort of functions like a big secret _ very few adults have heard about it, but among kids announcing a loss is instantly recognized.

Chelsea Johnston, a 16-year-old student in Vancouver, says about half the people in her Grade 11 classes know about the game. She describes realizing just how common it was when a friend lost at the mall, causing everyone in her group to exclaim aloud.

"Then we heard a couple of people, just random people, in the store say it, which was quite amusing,'' she said.

"And the store lady just gave us the weirdest look, she had no idea what was going on. And we had to spend five, 10 minutes explaining it to her.''

For some, the effort behind the slippery concept of thinking about forgetting is just too much. So they focus on making others lose, going on the concept that as long as others are losing more often, they're still coming out ahead.

"You can leave notes for people. There are certain key words that you can use that will remind them _ the game, losing,'' says Zakay. "People have sent me e-mails, notes, anything that will make you kind of unsuspectingly pick something up and get surprised.''

Strategies and hints on how to do this are a popular topic of discussion on the Facebook group and on www.losethegame.com.

Ideas include penning the website along the bottom of money. That leads whoever ends up with the bills to either lose immediately, or follow the link to learn about the game and, therefore, lose. There's also changing your MSN name to include a reference to the game, so that every time you log on, you set off a chain reaction of loss among the friends who see it.

The very idea of the game infuriates some people.

"Many people say that the game is pointless, which it is,'' says Haywood.

"But my argument is that kicking balls around a field and into a net is pointless, too, as are most games.''

"The purpose of games is to pose a challenge that's fun to play.''

Johnston said she often gets a negative reaction when she tries to explain the game to adults.

"Some of them have a good laugh with it, and join along for a while, then they might leave it,'' she said.

"But a lot of them, I find, just look at it as a waste of time.''

What seems to ruffle some people's feathers is that this isn't really the kind of game you can win.

"I guess once you start playing, you can't really stop,'' says Zakay.

"It's with you for life. I guess the point of the game is to not lose before you die.''