THE GROMS PRESS FORWARD, inching eagerly toward the arena entrance. Mullet-haired rampheads, bescabbed halfpipe urchins, scuffling along in their clompy skate shoes, their laces tied with a precise looseness. Eight thousand zitty faces lit with incipient testosterone, waiting to be shown revolutionary ways in which Newtonian physics can be warped, postponed, and dicked with.

They've come to the Mandalay Bay Arena in Las Vegas for a new kind of entertainment, a show that pumps the raw crude of male adolescence, a hormonic convergence of phatness and sweetness and straight-out sickness. These young acolytes have come for amplitude, for stunts and biffs, for grinds and grabs and serious air, for loud music and fumy motorcycle farts.

They've come for the Boom Boom HuckJam.

Once through the doors, the grommets come face to face with the thing itself. Behind a scrim of netting lies a baroque installation of giant stages, jumps, and ramps glinting in a swirl of strobe lights. Soon the chanting begins toe-KNEE, toe-KNEE, toe-KNEE the whole arena surging with raw skate-kid wattage.

Tony Hawk is the mind and wallet behind this unprecedented show. It's his private experiment, designed as a two-hour adrenaline extravaganza, a busy amalgam of motocross, BMX, and live music, with vertical skateboarding taking center stage. Tonight is the live debut of the HuckJam. It represents a huge financial gamble for the 34-year-old skateboarding venture capitalist; nearly $1 million of his own money is invested in this modern vaudeville act, which he will take on the road this fall.

Toe-KNEE, toe-KNEE!

To my immediate left, sitting with his dad in the VIP section, is Jonathan Lipnicki, the bespectacled 12-year-old child star of such movies as Stuart Little and Jerry Maguire. Lipnicki has been a Hawk fan for as long as he can remember. "Oh yeah, Tony's, like, the greatest!" he says.

Now the circus-barking announcer starts whipping up the crowd: Las Vegas! We need a little thunder!