Liga, performed thrice by the Dutch theater troupe Kassys at the Pittsburgh International Festival of Firsts last week, is a show whose layers of meaning at first seem to unfold slowly. But then you realize that you're grasping its undercurrents almost in real time.

The first "act" of this intermissionless and disarmingly comic work engages: It's a video projection of a mockumentary about actors slipping backstage, one by one, as their unnamed live show ends. Then, the five actors enter the New Hazlett Theater stage, one by one, in person. (Proving that the PIFOF's roster of U.S. premieres holds many pleasures, including the linguistic, the three men and two women are named Thijs Bloothoofd, Harm van Geel, Esther Snelder, Marc Stoffels and Willemijn Zevenhuijzen.)

Initially, it's confusing: The actors seem to simply wander the prop-filled space, with its big pillows, small tables, folding ladder and inflatable palm tree. But as the random motion gells, it comes clear that they're portraying a bunch of little kids. It's playtime. They misbehave; characters played by Kassys co-founder Liesbeth Gritter and on-stage technical director Klaas Paradies impose order. Eventually they turn the random play into work assignments, and soon we're watching five adults at a barbecue.

The show is wonderful theater: There's inventive near-constant and motion, and the Hazlett's whole playing space and then some is used; the characterizations of toddlers (each with a distinctive personality) are spot-on and built to a hilariously anarchic climax. But as the video intro makes clear, with its actors being coddled and reassured like children, the show is also a wry meditation on theater itself. The closing scene, which gets the actors back offstage, is sharply conceived meta-theater.

Ultimately, though, the humor is poignant: The five kids' unselfconscious (if destructive) play is supplanted by the need for approval and pragmatism, and we're left with five awkward adults mouthing platitudes and bad puns, their imaginations colonized by movie and TV references, all of whom keep talking simply so they don't have to think.

"This acting in daily life thing fascinates me," Gritter, who also conceived Liga, said in the audience talk-back after the Oct. 17 show. She likes the idea of grownups playing children who pretend to be adults. But I thought Liga spoke for itself pretty well, too. Though you're never ahead of the show while watching it, when it ends you feel you've grasped most of what it has to offer, with just enough enigma left over to make it memorable.