There’s no problem you can’t distract yourself from by hitting an opponent over the head with a war hammer.

That’s what Josh Hornthal has always thought. Not that the 13-year-old San Franciscan has ever wielded medieval battlefield paraphernalia. He just loves video games.

Playing sports games on his Xbox is cathartic for Hornthal, and, when he started thinking about a cause he could put his bar mitzvah donations behind, the idea of spreading that catharsis to people who really needed it appealed to him.

So, Hornthal proposed to the staff of San Francisco’s Koret Family House — a residence for children being treated for cancer at UCSF Medical Center and their families — that he install a few XBoxes for their young clientele.

Family House Executive Director Alexandra Morgan agreed. But she had no idea what she was getting into. Because Hornthal didn’t just dump a video game system on her front step. Instead, he demonstrated organizational and business acumen astounding for a boy his age, exceeding his own expectations and those of his parents, Bethany and Jim Hornthal.

His lobbying for the Tech Mitzvah Fund paid off to the tune of more than $3,000 — six times what he’d hoped to land.

“In the beginning, when I got my first couple of donations, I wanted to run down to the bank and cash them. I thought it couldn’t get much bigger. But then they hit us,” said Hornthal, something of a technical savant who has designed Web pages for local artists and is sometimes called upon to show his parents’ friends how to operate their high-tech gadgets.

“We ended up with so many more options.”

With cash in hand, the boy once again showed wisdom beyond his years, and bargained with hostage-negotiator intensity to get the very best deal.

The folks at Circuit City were so impressed, they tossed in an extra Xbox, free. And Best Buy gave him the employee discount.

So, at the current time, Family House’s dozens of young patients can currently take each other on in more than 30 games on six different Xboxes. And Hornthal, who has been charting his donations on an Excel spreadsheet, still has $1,000 in the can.

But it gets better. When Hornthal asked what that extra grand could provide for Family House, they asked for DVD players. But the tech-savvy youngster saved the house a bundle when he, instead, bought a handful of remote controls and informed his elders that the new video games systems would now play DVDs as well.

“One kid just came back from the hospital from his most recent treatment, and I sat him down and popped in ‘Finding Nemo,'” recalled Hornthal, who had his bar mitzvah at Congregation Emanu-El on Sept. 11.

“He had a blast.”

In fact, the reaction to the new Xboxes has been universally ecstatic.

“One of the kids, when he saw it, his mouth dropped open and he ran back to his sister and shouted at the top of his lungs, ‘They have Xboxes!'” said a laughing Hornthal.

“That was the greatest reaction.”

Hornthal isn’t walking away from his project, either. Every Friday, he plans to head to Family House and take on all comers in an Xbox challenge.

“He’s doing something for children he doesn’t even know. That shows me what a remarkable person he is,” said Morgan, the house’s executive director.

In the future, “I hope he takes over some huge leadership position.”

Contributions can be made to Family House, 50 Irving St., S.F., 94122, and earmarked for Tech Mitzvah Fund.