When you play the game Peggle, do you think everything is left up to luck, or skill?

As it turns out, the answer to this question might say a lot about the nature of gamers – and what makes someone a casual or hard-core player.

In case you haven't heard of Peggle, it's a title that came out from PopCap Games two years ago(and a new version was launched a week ago on the Nintendo DS). PopCap is the current king of casual games, those little in-browser gewgaws played by tens of millions of people who do not, normally, play any videogames at all – like moms and grandparents (or cubicle workers seeking to anesthetize their humdrum existence).

PopCap has been the giant of casual gaming. Indeed, the company pretty much single-handedly created the trend with its 2001 game Bejeweled, which has placed more than 500 million people into a glazed trance. PopCap quickly followed up Bejeweled with other games like Zuma and Bookworm, all of which went on to become casual hits.

Why are PopCap games so popular? If you ask most game designers, they'd say it's because PopCap perfectly understands the psychology of casual gamers – and what makes them different from the hard-core crowd.

The dividing lines are generally understood to be two: simplicity and time commitment. Hard-core gamers are willing to deal with incredibly complex game interfaces – like inventory-management systems, bewildering arrays of power-ups, controllers festooned with a dozen buttons and triggers. They like the flexibility the complexity gives them. They're also willing to commit 10 hours in a row to master a game.

Casual gamers are precisely the opposite: They want super simple games you can learn instantly and finish playing in a few minutes. When it comes to simplicity and time commitment, these two styles of gamer are poles apart.

So when PopCap released Peggle, it looked like another game tailored perfectly for casual folks.

Peggle, for those who haven't played it, is like a digital-age version of a pachinko game. You drop 10 balls down into a constellation of pegs, and they bounce downward until they reach the bottom. Each time they hit a peg, they eliminate it; your goal is to clear all the red pegs before you run out of balls. The rules are incredibly simple, and the game can be played in minutes: A natural for casual folks, right?

Except soon after Peggle launched, PopCap discovered something weird: The game was becoming a hit amongst hard-core gamers, too. And while many casual gamers also loved it, others found it a turnoff. Why?

The PopCap guys have several theories. Possibly the game's psychedelic graphics freak out casual folks; possibly the "passive" style of play – you drop the ball, then silently watch as it bounces around the screen – is slightly foreign to the nonstop-clicking vibe of most other casual games.

But when I chatted with Greg Canessa, a PopCap vice president, he suggested another fascinating theory: That hard-core and casual gamers have different views on the role of luck in the game.

For a casual gamer, Peggle seems too heavily based on luck. You aim the ball, but once you've dropped it and it hits the first peg, all bets are off: It bounces and careens through the forest of pegs in crazy, zigzagging patterns. For casual players, there doesn't seem to be a clear enough correlation between how they aim and the results.

But hard-core gamers see the game quite differently. When they look at the Peggle board, they see the Euclidean geometry that governs how the ball falls and pings around.

"They'll be sitting there thinking, 'Oh, if I bounce the ball off that peg it'll hit this other peg and jump over here, where it'll take out two other colored pegs," Canessa said.

In other words, hard-core players are comfortable mentally manipulating Peggle's complex physics. They can build models about where the ball is going to go, even after the seventh or eight collision. A frustrated casual gamer looks at Peggle and sees chaos; a hard-core one sees causality.

(And, being hard-core gamers, this immediately puts them in an absolute lather to try and master the game. Indeed, one key to succeeding at Peggle is predicting bounces so far in advance that you can win extras by having the ball land in the traveling "rescue" slot at the bottom of the screen.)

The really interesting thing is that – assuming this theory is true – the casual players are misperceiving the role of luck in the game. Bejeweled, PopCap's single biggest hit with casual gamers, is in reality far more luck-based than Peggle. Both types of gamers are seeking out games where they have some sense of control; that's part of the fun of a game, after all – a controllable environment. But the hard-core players are able to see past the apparent luck of Peggle, and to spy its underlying – if extremely complex – rules.

Maybe this is another way that hard-core and soft-core gamers are psychologically different. When you look at a game – hell, maybe when you look at life – do you see everything governed by chance and fate? Or are things up to you?

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Clive Thompson is a contributing writer for The New York Times Magazine and a regular contributor to Wired and New York magazines. Look for more of Clive's observations on his blog, collision detection.