On a nice weekend day if you go to Fire Island's Ocean Beach, hang a right, and walk along the shore a few minutes, you're likely to come upon a group of six people standing in a circle around a yard-high, plywood pyramid. One of them will bounce a ball off a face of the pyramid, someone else will try to catch it, everyone will suddenly start dashing back and forth putting on moves, and the ball will fly around the circle of players until somebody misses.

It looks like a Keystone Kops scene in the sand, until you go over and talk to Mark Miller, who will gladly take time to explain the game and unlock the mystery of . . . Trangleball. It's his baby, his invention, his ticket, and this isn't just another day at the beach, it's marketing. If everything goes his way, Spalding and Wilson will be in a bidding war for this game . . . no back yard, beach, playground, or rec room will be complete without some version of it . . . ESPN will have to pick it up . . . volleyball will become passe . . . Trangleball will become the game sensation that rocks the nation!

Why? Because it's fun, and easy to learn for anyone who can catch and throw - it's a good game. After one afternoon of diving in the sand, figuring out the angles and some strategy, and having some extremely good-natured competition, I can say without reservation that I want more Trangleball in my life.

Which is exactly the effect Miller is hoping to have, "I bring it out every weekend so people know it's here, they'll talk to their housemates and say 'Hey, let's go play that game.'"

Miller figures he'd get more attention if he was at the more heavily trafficked Westhampton Beach, but for now, his plot here at Corneille Estates is working out fine. "The response has been unbelievable." But when people ask if they can buy a version of the game, he says no.

"I'm trying to sell the concept of the sport and educate them, I'm not trying to sell the game on my own." He wants to get one of the big sporting goods companies to do that, but in order to accomplish that, he has to have something to show. The day I tripped over this scene, Miller was giving away T-shirts to anybody who played the game. The more people play, the better the games will become, the better the promotional videotape he's making will look. The guy who's videotaping as we speak is the DJ at one of the Ocean Beach bars, and he's going to play the tape tonight on the big screen. Talk about hitting the angles.

While we're talking at the side of the court, there's a vigorous game in progress. One guy dives for the ball, realizes he can't catch it, and tries to keep it alive by tipping it to a teammate. Miller loves it. "If you're willing to give yourself up to the sand, you do much better," Miller explains. It's music to his ears when a player swears, means the guy is really into it.

Like so many other great things, Trangleball was born in Brooklyn. It started a couple of years ago with Miller bouncing a ball off the corner of the ceiling in the recording studio he owns. One ridiculous adaptation led to another - in trying to build a portable corner he inadvertently discovered the pyramid - and by last summer Miller had his game figured out. At that point, it was a closely held secret, so he called it "Shh-Ball."

The scene on the beach where they play is groovy in a postgraduate beer-commercial way. The clientele is mostly house-share singles, classic rock blasts from a box, beach chairs cluster around coolers. The game attracts a crowd of onlookers, and it puts grins on their faces because play often looks foolish. ("when it's not pretty," says Miller, "it's not pretty"). But, of course, to play is the thing.

In one-third of the round court, you're pitted against one player from the opposite team, and you have a teammate in each of the other two sections. The object is to bounce the ball (squishy plastic, the size of a softball) off the face of the pyramid facing you so that your opponent can't catch it. Or you can throw it to a teammate who appears to have position on his opponent. You can run with the ball, which changes all the angles, so all the players have to adjust. (The angle of inflection equals the angle of deflection, or something like that.) All it takes is decent hands, game sense and a sense of humor. It seems impossible to take the game too seriously - perfect for the beach.

After a warm-up game in which Miller taught me how to lose badly at Trangleball, I was teamed up with a couple experienced players. We held the court for four games, undefeated, even beating a team that had Miller and the guy with the rep as the best player on the beach. I share this information not to brag - not much - but as evidence that the game isn't very difficult to pick up.

My teammate, Howard Friedman of Forest Hills, said he's been playing every weekend since the beginning of the summer. "I find myself thinking about it all week," he said. "I think about the physics of it, I figure out the angles."

Our most successful bit of teamwork was like a second baseman-to-shortstop double play combination. Friedman would run toward me, and I'd flip him the ball while his opponent was out of position; then Friedman could hit the face of the pyramid and bounce the ball to the sand for an easy point. Willie Randolph would be great at this game because he can throw that little backhand flip with great accuracy; he'd run past the trangle and be able to shoot or pass from any position.

Miller sees the game as a work-in progress. Even now he's refining the rules, envisioning other games to play off it. (1-on-1, single-double-triple), thinking of other formats (tabletop, for instance), targeting new markets (phys-ed. classes), the sky's the limit. Just ask the rich guy who invented Frisbee.

"It's a vicarious thrill for me to watch people play," he says. "It's like someone is appreciating my art with every dive they take."