While harried streams of undergraduates rush to get to classes on time, one small circle of students stands in a ring in the Yard, oblivious to their surroundings. They are helpless--addicted to a little-publicized habit.

"I learned it from the natives in Indonesia while I was working there for an anthropologist," says Manuel E. Lerdow '86-'87.

"I did it in high school when a couple of my friends started," says David H. Cohen '89.

'I taught myself in my living room all winter long...I had no friends," says Jonathan E. Sinton '86.

The focus of this obsession is humble in its size: it is merely a small, round beanbag resembling a miniature baseball in design. To devotees of the sport of Hackey Sack, however, the bag's significance is quite large.

The goal of hacking seems straightforward enough: participants toss the sack up in the air and begin a binge of "hacking." According to the World Footbag Association, the object of the sport is merely "to keep the Hacky Sack off the ground using the lower part of your body, mainly your feet and knees."

Although it appears so innocent, it rarely stops there. Players agree that, once you start, it's almost impossible to "kick" the habit.

"We used to play for hours every day," says Cohen. "Of course, you skip class to hack."

Although the concept of hacking is simple, the methods used vary. There are the basic instep and outstep kicks. In addition, there are the more exotic knee bounces, chest traps, and the ever popular toe shot.

"Just the hands are illegal," says Lerdow. "Head, ears, neck, knees--even buttocks are acceptable."

Although hackers have a complex code of etiquette, they are hard pressed to list rules to the game. "There are two rules that are almost accepted," says Charles S. Zender '86-'87. "One is that you can't say you're sorry if you mess up. The other is that if you do, you suffer hack punishment."

Sinton explains that this consists of "hurling the sack at various parts of your body, the exact part depending upon the seriousness of the infraction."

If the rules of Hacky Sack are ambiguous, the criteria for a "win" or "loss" are even more so. "Hacking is a noncompetitive, team-oriented game," says Cohen. Adds Spence, "It's like Yin and Yang, winning and losing--even on the worst hack you do something, and even on the best hack, you lose in the end."

Lerdow agrees, "It's a great game because you can never really win. I like to think of it as that there're no winners, only losers."

More than mere recreation, hacking is a social activity. "You meet a lot of good people hacking," says Spence. Cohen interrupts, "And anybody who's coordinated can be good at it."

Although hacking can be extremely strenuous to a novice, Lerdow says, "It doesn't really affect you too much physically. I wouldn't recommend it as a form of aerobics or anything."

"When you start out,"adds Zender "a lot of the exercise comes from spelunking down the sewers" after badly placed shots.

Hacking, say players, has a long and illustrious--if somewhat apocryphal--history. "In China they do it with a harder ball, in Thailand, with bamboo pieces; in Cambodia, they use nuts hackers report. "But you can play with just about anything...anything circular that is," says Zender.

"There are many myths of Genesis floating around," he adds. "Just about the only thing you can be sure about is that it's here."

The official Whammo Hacky Sack is made of plastic beads coated with animal hide. "If you don't eat meat, it's hard to justify playing Hacky Sack says Lerdow. "That's the only trouble--thinking about all the dead animals the went into it."

Hackers say they often take then sacks on the road with them. "You play anywhere, everywhere you can," says Greg D.S. Anderson '89.

Zender says, "The weirdest place I've ever hacked are on the slopes of Mt. Olympus in Greece and on a raft in the Mississippi." Adds Lerdow, "On the steps of the Capitol."

At Harvard, prime playing spots include in front of Lamont or Widenet although the Yard is off-limits for about three months before Commencement "when they try to keep the grass looking nice," according to Zender. Also, hacking has been permanently banned in the Quincy House courtyard because of the danger it poses to windows.