Caught in the midst of another afternoon Peggle bender, I knew all the reasons why I had been sucked into the game. But teaching a heroin user about neurotransmitters and the blood-brain barrier isn't going to stop him from getting his next fix. The developers themselves have admitted there's sound psychology behind their design decisions, like tones that subtly rise in pitch the more pegs you hit in a single combo.

There's (presumably) sound psychology involving the game as well. Last year, East Carolina University conducted a study on the effects of playing PopCap games on short-term mood and stress levels. Researchers concluded that Peggle improved the average test subject's mood by 573 percent, reduced anger by 63 percent and reduced confusion by a whopping 486 percent - not bad for a game involving unicorns, space aliens and skateboarding gophers! (These findings are mitigated somewhat by the fact that PopCap funded the study, however.)