About 20 people in their early twenties are playing four square in Rittenhouse — mostly slim men with cut-off shorts or rolled-up denim. Some hold cigarettes in one hand, taking drags as they bounce the ball with the other. Instead of chalking their boundaries, the players use the brick pattern of the Square to delineate the court, a 10-foot by 10-foot box evenly divided into four sections.

Four square is a simple game. One person stands in each section of the court. The “King” of the court serves the ball — these four-squarers only allow underhand — into the opposite player’s square. Players must hit the ball into another’s square before it bounces more than once in their own. The game requires hand-eye coordination, quick reflexes and solid footwork.

While their Nike hi-tops and mohawked heads channel a “too cool” aesthetic, the four-squarers invite others to play indiscriminately — young folks, old couples, people with athletic builds and still others who have probably never touched a playground ball in their lives. The four-squarers shout out to passersby, “Hey! Come join us! Come play four square!” Sometimes they might applaud to encourage interested spectators. The four-squarers are definitely cool, but they're inclusive too.

A group of five men and women in their forties slow down on their walk through the Square to check out the game. One member of the party whispers, a little too loudly, “Oh look! Volleyball!”

“FOUR SQUARE!” the players shout, not so much in outrage as in jest. As a male friend of the mistaken woman kindly explains to her what the game of four square is, the group encourages both to join.

For most Rittenhouse Square parkgoers, the playground sport gives them pause — a mere flicker of nostalgia. But then the reality of not remembering the rules or fear of embarrassment sets in. The middle-aged group stands there deliberating amongst themselves in whispers, but finally leaves after the woman concludes loudly enough for the four-squarers to hear, “Next week. Next week.”

For kids on the playground, four square is an equalizer. Well, sort of. You don’t have to be particularly athletic. Essentially everyone can play; it’s just a matter of intensity. Also, once you’re out, you’re only out for that round, not for the entire game. As such, four square isn’t just for four people as the name implies — if you’re willing to wait, four square can accommodate about 20 people comfortably. While you wait for your turn, you can chat with your fellow players. Or, as in the case of the Rittenhouse four-squarers, you can also smoke a cigarette, swig from a brown paper bag or share a sip of your girlfriend’s La Colombe coffee that she just bought from down the street.

Some four-squarers play intensely, turning the game into an ultimate version of the playground favorite. Serving underhand allows four square to be played low to the ground and as such, faster. It becomes a game of skill and agility. You must anticipate where the ball will travel. Hitting the ball in corners is best; slow players can’t get there quickly enough. Some players dive with their bodies parallel to the ground (think Ultimate Frisbee) just to deflect the ball. They dart into adjacent squares to hit the ball, while their slower opponents stay frozen in their spots.

Roommates Patti Colli and Helen Tiller, recent graduates of the Art Institute of Philadelphia, are part of the Rittenhouse four square crew. Patti is petite and slim with wavy brown hair. Helen is stout with thin blonde hair tied back with a scrunchie and a hearty, scratchy laugh. Helen shouts for Andrés Garcia, a young man with a calf tattoo who is clearly a leader of the group, to come over. He asks Patti and Helen to go on a water run for him, which they playfully agree to do. There is an obvious sense of camaraderie among the players, all centered around a game on the street.

At Rittenhouse an hour earlier the next week, the energy of the game is entirely different. Or perhaps, it’s just the energy surrounding Rittenhouse that changes. Two toddlers screech in excitement for four square, happy just to be watching. Kids hula hoop in the dry fountain next to a woman swirling about with white flags under her arms. A group with bells on their ankles perform a synchronized dance that involves touching feet and tapping wooden sticks in rhythm.

Patti is the only recognizable member of the Rittenhouse four square group from the week before. About two or three kids still in elementary or middle school begin to play. The four-squarers seem amused with one boy sporting a fedora, especially when he cruises through three squares, knocking out players twice his age. More people join the game until the line encircles the court.

A man in his thirties approaches Patti. He wears black dress socks with sensible-looking running sneakers. His hair is thin and brown, messily styled with a bit of wax. His features, especially his nose, are sharp, emphasizing his slim build.

“You going to join us? Do you know how to play the game? Would you like me to explain the rules?” Zack Lane asks warmly, in a startling nasal pitch.

Patti suppresses her smile to thank Zack and promises to play a bit later.

Zack and Andrés ­— the tattooed man from the previous week — are the organizers of Rittenhouse Four Square. They act as welcoming agents between the Rittenhouse four-squarers and Rittenhouse parkgoers.

Zack has a more direct approach than Andrés. By spending more time outside of the four square court, he speaks to parkgoers more frequently. When a new player joins the game, he announces to the King “Newcomer!” to prompt him or her to serve the ball gently. If a newcomer becomes King, Zack quickly mentions a few of the basics like “serve underhand to the person directly across from you.”

The best option for a less-athletic player who can’t move quickly is to play defensively. Rather than playing to eliminate another, defensive four-squarers play just well enough to stay in the game until an aggressive player spikes him or her out.

But who’s in and who’s out isn’t always so obvious. At the end of one round, the ball bounces somewhere between the boundary line and a player’s square. As one player walks off the court, a voice comes from above, “You’re in.” A lanky man wearing a bandana holding back his brown dreads sits about eight feet above everyone on an urn in the middle of the brick wall behind the court. “You’re in,” he repeats to the player. “Well, if God says so,” say the fellow four-squarers, shrugging their shoulders and laughing. And so he becomes God on the Urn, the de facto referee.

This July, the Rittenhouse four-squarers hit a roadblock when police enforced the ban on ball-playing. For the next three weeks, the four-squarers played in the parking lot under the bridge on Chestnut and 24th Streets and even went as far as the Piazza in Northern Liberties. The group shrank significantly. Only the devoted came, mostly the founding members of Rittenhouse Four Square and those who followed their updates on Facebook. The diversity of pick-up four-squarers was lost.

It seemed a minor issue though. This was a rule the police had attempted to enforce the previous summer, and the four-squarers were able to resume their usual game after a few weeks. After an article about the ban ran in the Philadelphia Inquirer in late July, they resumed play that evening in the Square with more four-squarers joining as a result of the publicity. Since then, the four-squarers have been playing on Mondays and Wednesdays at 8:30 p.m. (a later time so as to avoid the crowds and police) without protest.

A few of the core four-squarers reside in South Philly and, like many players of Rittenhouse Four Square, are essentially big college kids. They aren’t exactly adults yet or don’t see themselves as such. There isn’t that sense of “settling down” with a 9-to-5 job, and they seem content with delaying that as long as possible.

Andrés and another Four Square organizer, Shaka Moody, reside together on Christian Street. The numbers on their doorway are painted red with the “6” slightly askew.

The smell in their home, left over from a barbeque they had thrown a few weeks ago involving forty pounds of chicken, is of ripe, rotting meat. Clothes are strewn everywhere, and a half-naked female headless mannequin — salvaged from a dumpster in Virginia — sits askew in their living room.

Mondays are Stoop Mondays at their house. Shaka, who doesn’t work on Mondays, generally begins “stoopin’ it” with a sweating brown bottle of He’Brew at four o’clock, while other four-squarers join him as their lax (or lack of) work schedules will allow. Shaka is certainly the most well-dressed of the crew. He pairs perfectly dirtied Vans with fitted black jeans, and his crossword puzzle checkered T-shirt and Prada tortoise-shell glasses are delightfully nerdy chic.

Andrés credits Shaka with making four square a summer institution at Rittenhouse. Shaka played four square in middle school while he still lived in Virginia; his father worked at the recreation center in Richmond where he played on a “regulation court.”

The Philadelphia four square tradition began the summer of 2008 when Shaka graduated from college and Andrés was just a year out. They lived together at their current address with other college friends from the Institute of Art.

It was that summer that the group played capture the flag behind the Philadelphia Museum of Art, tried stand-up comedy at Helium Comedy Club on open mic nights and began playing four square in Rittenhouse. Originally they joined a four square game that was already going on in the Square, but when they came the same time the next week, the group was gone. And so the tradition began. Zack Lane, the “CEO of Rittenhouse Four Square,” who they knew through mutual friends, created the Facebook group “Rittenhouse Four Square,” making them the administrators of weekly updates on the time and location of the game.

Shaka has also created a vision for a 16 square game. Four teams of four would play on four connected four square courts that would form a larger 16 square court. The people on the innermost squares would be the “fighters” while those on the corner squares would be responsible for saving the ball by hitting it back inside to them. “Double-tapping,” hitting the ball twice, would be allowed within the four square courts, to pass to teammates. To pilot-test this idea, Shaka hopes to have a cookout at the empty lot down at the end of Christian Street, where teams would sign up to play and party.

Contrary to popular belief, the novelty of a playground sport like four square is really most appreciated by those in their early twenties, like Shaka and Andrés. Upon entering college, some of us become better kids than we were when we were actually kid-aged. We might begin climbing tress, wearing candy necklaces, or finger-painting again.

Now, we can play four square.