For 18 years, Karla Boos has chosen what plays to stage because of some inner chemistry, whether in them or her. But her latest venture, Shakespeare's "Cymbeline," has the director-actor-visionary of Quantum Theatre feeling "loose and light-hearted."

One of Shakespeare's last plays, "Cymbeline'' is the one few people have seen and one of the most enigmatic, variously classed as a comedy, tragedy or even history play, but usually as a romance.

In spite of being better known for premieres and contemporary works, Quantum has done a number of Shakespeare plays over the years. But what's unusual, doubly so, is that the company that always seeks out new non-theater places to perform is returning to one it has used before -- twice. That's the formal garden in Mellon Park, where it previously staged "Dark of the Moon" and "The Crucible."

Boos promises the site will feel new, in part because Quantum has built a Shakespearean thrust stage that she describes as being akin to "a giant spaceship." And then there are the costumes, which in Quantum are often minimal but not so in this case. Designed by Susan Tsu of Carnegie Mellon University, they have "a little goofy, futuristic look."

As interesting as the design and outdoors setting will be, Boos believes that the text will take precedence, with both its comically complex plot and its poetry. At about 3,300 lines, "Cymbeline" is one of the longer of Shakespeare's plays, but Boos says she's pruned the text sharply, cutting it down to just two hours plus an intermission.

Further, while it calls for some two dozen roles plus any number of other lords, ladies, senators, musicians, captains, officers, soldiers, messengers and attendants, Boos is doing it with just seven actors. Miki Johnson will play Imogen, while Rick Kemp, David Whalen, Patrick Jordan ("his first Shakespeare"), Joel Ripka, Sam Turich and Mark Staley play everyone else, on average three characters each, male and female. Boos calls this casting whimsical, which she says mimics the play.

And there's also a technological aspect involving robots, about which Boos doesn't want to talk at all, both because it's not central to the play and because she counts on the surprised audience to figure out how to respond.

"If you're not alert and ready to participate, you may miss your opportunity," she says. "We're interested in what we can't control, which includes the audience, and something deeper. ... I think Quantum is known to ask quite a bit of the audience, to challenge some assumptions. We want the audience to bring their half to the experience."

Indeed, the audience is the reason for the Quantum name, which alludes to the dictum in quantum physics which says that the act of observation changes the reality of what's being observed. As to how this relates to Quantum's collaboration with the Carnegie Mellon University Robotics Institute, we'll have to wait until the play opens tomorrow to discover.

The outdoors set, small ensemble cast and robotics are all being expended on a play Boos says she has loved "ever since I was young." But she's producing it only "now that I dare relate to a later-career Shakespeare [which moves] through cynicism and out the other side. He comes to some hard-won conclusions about human psychology.

"My inclination is to like the experimental late plays. I guess I also just respond to Imogen. She's without flaws, but she's no cipher -- she's so active, such a source of pleasure. ... I'm sure in loving plays I slough over their flaws. I definitely make an emotional decision."

She's perfectly aware of the "goofiness" of a twisted plot that parallels Imogen's separation from her father, the British King Cymbeline, with Britain's split from its imperial "father," Rome. In the process, Imogen marries for love, is betrayed by a villain come from Italy and has to disguise herself and go into hiding. Meanwhile, the king's second wife plots on behalf of her doltish son, and what of the king's two sons by Imogen's mother?

That's just a hint at the intertwining of the plot, which comes to a head in one of Shakespeare's greatest final scenes, where revelation follows revelation, the dead are brought to life and the separation of child from parent is addressed on both the personal and national levels. "It's moving to me that Shakespeare believed in that psychological journey, the coming out from a dark tunnel," Boos says.

"But sure, we're playing for laughs," she promises. "It's a house of cards." And she has fun with the doubling. One actor, for example, plays both villains, the lying Iachimo and the duplicitous queen. Another plays both the British king and a Roman general.

What will people make of it all? As always, Boos is counting on her audience. But she says that's not how she starts a play: "I don't ever think about will it sell, just about if it will work. Sometimes my judgment is commercially viable, sometimes it isn't -- I just try to make it work aesthetically."

It's natural to segue from this to the economics of producing art theater. "Cymbeline" is the first show of Quantum's new four-play season, "when we take people's money for subscriptions," as Boos puts it.

In light of the season shortfalls reported by both City Theatre and Pittsburgh Irish & Classical Theatre, she is pleased that Quantum subscriptions are holding steady or even increasing. But Quantum's frugal annual budget is $670,000, compared with PICT's $1.3 million, City's $2.9 million and the Public's $6.3 million.

"It's a good time to be small and fairly inexpensive," Boos says. Quantum has a spare, full-time permanent staff of just five. "Each does everything from the most sophisticated job to the least," from tasks that "challenge the highest levels of their skills and knowledge to those that use their hands."

She is glad to keep Quantum small. "It seems so burdensome to grow that big. I want to sleep at night. I definitely weigh the growth of the organization against how much time I have to do the work," whether directing, acting or producing. "I'd be afraid I wouldn't be able to be as fearless as we are."