When Alexey Pajitnov put the finishing touches on Tetris 25 years ago today, he had no way of knowing his modest videogame would become Russia’s most entertaining export.

Yet June 6, 1984, has become a landmark date in the history of videogames: That’s the day the then-29-year-old computer programmer completed his first playable version of the fiendishly addictive game that would launch a thousand clones.

What made Tetris different? The game was graphically elegant and easy to grok: To play, you arranged seven different kinds of falling blocks into a tower without letting them pile too high. The game was so straightforward and simple that anybody could pick it up, yet as play progressed Tetris became more and more challenging.

People still play it, says Pajitnov, not only because it’s an excellent game but because for many people, it was the first videogame they ever tried.

“It’s like your first love — you never forget it,” he says.

The game’s simplicity and appeal has made it the archetypal videogame: referenced in popular culture, studied by scientists and still wildly popular.

Tetris was unlike any other videogame, mostly because it was (and still is) played by as many women as men, as many adults as children. More than 125 million copies have been sold so far on more than 50 different gaming platforms, which Guinness World Records recognizes as the most versions of any single videogame.

Another differentiating factor: Tetris was owned by the Soviets.

Since Pajitnov was an employee of the Soviet Academy of Sciences, he had no rights to the game he had created. But the government was happy to license Tetris to companies like Nintendo, which coupled the game with its revolutionary Game Boy platform, turning both into breakout hits in 1989.

The Tetris Company, which manages the rights to the game now that they have reverted back to Pajitnov, says that Tetris represents fully 10 percent of all mobile games sold in the United States.

At the Academy, Pajitnov’s work involved computer science research like artificial intelligence and speech recognition. In his spare time, he loved to play with puzzles and math riddles. When his department got a new Elektronika 60 computer, a Russian clone of the PDP-11, he began to create computer game versions of several of his puzzles.

“Tetris was just one of my games at that time,” he says. “Most of them were just boring experiments.”

Image courtesy The Tetris Company

Since the Elektronika couldn’t display graphics, Tetris‘ tetromino pieces had to be created out of text brackets. But even in this primitive form, Pajitnov found that the game was already tons of fun.

“There was something new and simple and sublime in Tetris,” says Georgia Tech media studies professor Ian Bogost, who attributes much of the game’s success to its first-mover advantage. “There weren’t a lot of original ‘casual’ videogames in the mid-1980s, and Tetris has managed to become the ur-casual game. It persists, in part, because it was first.”

Pajitnov, along with some programmer friends, soon began work porting the game to the MS-DOS platform. This version of Tetris spread like wildfire around the world on copied floppy disks, catching the attention of many game publishers.

Nintendo pegged Tetris as a perfect launch game for its portable game machine, Game Boy.

“We had popular games already at that time, like Super Mario, Zelda and Donkey Kong,” says Minoru Arakawa, former president of Nintendo of America and current president of The Tetris Company. “But they weren’t a great fit for Game Boy.”

Nintendo’s engineers in Japan thought Tetris was perfect — a simple game suited for playing on the go, but also suited for the Game Boy’s small, monochrome display.

After a convoluted series of legal machinations (recounted in depth in the book Game Over Press Start To Continue), Nintendo successfully negotiated with the Soviets and emerged with the worldwide rights to create handheld and console versions of the game. The Game Boy version alone sold 35 million copies.

Everyone’s mom swiped their Game Boy to play Tetris. It was so appealing to women, says Pajitnov, because it was a creative, constructive game developed when every other game was about destruction.

“You take the chaos of these random pieces and try to build something reasonable out of it,” he says. “Most of the videogames, shooting games, are about destroying something. And they don’t appreciate violence as much as we boys do, you know?”

Henk Rogers (left) and Alexey Pajitnov.
Image courtesy The Tetris Company

Once the Soviet Union collapsed and the rights to Tetris reverted back to Pajitnov, he formed The Tetris Company with his friend Henk Rogers, a game industry entrepreneur who had helped Nintendo acquire the Tetris license.

Rogers’ business acumen kept the Tetris name so bankable. The company’s latest venture is Tetris Online, which it says is played 1 million times a day.

“It’s not a fad,” Rogers says. “Tetris today is bigger than it’s ever been. It earned more money last year than in any year in its history. It’s outlasted every other game in the computer industry. It shows no sign of abating.”

Rogers has been making Tetris more marketable since almost the very beginning. Giving the player points for clearing multiple lines of blocks in a row, he says, was his idea. So was calling the ultimate move — clearing four lines at once — a “Tetris.”

“I wanted ‘Tetris’ in there so that people would repeat the word,” just as when players yell out “blackjack” or “Yahtzee” when they score the best hand in those popular games, he says. “And it actually worked.”

As the game became more and more popular, it attracted all sorts of attention. A study this year at University of Oxford found that playing Tetris could reduce symptoms of post-traumatic stress disorder. And a 1991 University of California study (.pdf) found major differences in players’ brain activity at various stages of Tetris mastery.

“The good players have almost a calm brain, but the beginners have very excited brains,” says Pajitnov.

Tetris‘ success caused a flood of copycats, launching the puzzle-game genre. But nothing has ever been as appealing as the original, which causes Pajitnov, lover of games and riddles, a good deal of consternation.

“I am desperate to see the new Tetris somewhere,” he says with a heavy sigh. “I am waiting every day for something like that.”

Not even the semi-retired Pajitnov has been able to create another game that captured the appeal of his big hit. But he has learned not to underestimate the casual audience. “People don’t realize that ’simple’ doesn’t mean primitive,” he says. “People still need to have a challenge all the time.”

Then again, maybe designing the perfect videogame is all about luck.

“I tried to put some science into game design, but later I understood that it is just a magic art,” Pajitnov says with a chuckle.

Have you recently teamed up with a mysterious druid in World of Warcraft that happens to love math puzzles? You could have been on a raid with Tetris creator Alexey Pajitnov.

“I recently started playing World of Warcraft, and I’m still playing it and enjoying it a lot,” Pajitnov said in a recent interview with Wired.com on the eve of his legendary puzzle game’s 25th anniversary.

Pajitnov is currently playing a level-74 female druid in the popular massively multiplayer online game. And it’s not his first character: He says he’s also played a warlock up to level 70 and a hunter before that.

He never tells anyone that he created one of the most popular videogames of all time, though.

“Nobody even knows that I am male,” he said. “I play just female characters.”

As you might expect, Pajitnov is interested in the MMO world’s complex game design. “It was very interesting for me, how the design works,” he said. “I really enjoyed the design work in Warcraft, because they must have a really huge team, and it was amazing how they distribute their activity and create together.”

Playing WoW has been “a very unusual experience,” he says, because in his 25-year career as a game designer, he has rarely gotten hooked on other people’s videogames. The only other games he’s played with the same level of passion were Nintendo’s Zelda games and the four-color CGA version of Lode Runner. (”I was absolutely addicted for more than a year.”)

Although Pajitnov mostly plays Warcraft solo, he has partnered with others on occasion.

“I’ve joined several guilds,” he said. “I did have a group which I used to play with a lot together, but later we lost each other and now I just have temporary alliances with different groups.”

So now you’ve got to ask yourself: Is that level-74 druid in your guild a game-design legend in disguise?