Seattle's Rat City Rollergirls get ready to knock each other silly on the road to roller-derby regional championships.

Roller-derby rules may be complicated, but its appeal is obvious. Take, for example, a recent Rat City Rollergirls bout that pitted scrappy underdog Grave Danger against undefeated powerhouse Derby Liberation Front.

The match incorporated the finesse and power that define derby — plus penalties, creative coaching and orchestrated mayhem.

DLF opened up wide leads, its “jammers” speeding around the track racking up points while Grave Danger “blockers” tried to knock them off the track. Grave Danger fought back each time, ending the match with a breathtaking scoring run in front of a screaming audience that leapt to its feet. DLF held on to win by a single point, 128-129, in a sport where victories are often lopsided.

On Saturday, the Rat City league’s four teams face off for the last time before sending an all-star team to battle for a regional title and a spot in the national tournament in November. Although eastern teams like New York’s No. 1-ranked Gotham Girls have dominated the national rankings, West-Coast teams are surging. Last year, Rat City’s all-star team came in 5th overall at nationals.

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This is not your mom’s roller derby, though it pays homage to its 1930s racing roots and the chair-smashing spectacles of the 1960s and ’70s. It’s grown into a bona fide sport with its own governing body — the Women’s Flat Track Derby Association — and dozens of leagues around the country.

The Rat City league was founded in 2004, the Northwest’s first. The name refers to a nickname for the White Center neighborhood where Seattle’s league originated; it outgrew several venues before moving to KeyArena this year.

Jennifer Warnick, who joined the league as Shovey Chase in 2005, went to see that first White Center bout. “In the first 10 minutes I was sitting there, I knew I had to play. There were these girls who looked beautiful — and yet they were pummeling each other.”

Although many favor makeup, costumes and body art, skaters are athletes, many with backgrounds in traditional sports. Rules prevent serious injuries in a fast-paced activity that looks more like speedskating than disco-era entertainment.

But old-school elements remain, including ingenious player nicknames. Rat City’s roster includes Selma Soul, Anya Heels and Georgia O’Grief. Teams and leagues come complete with groupies, cheerleaders and announcers — all of whom, like the players, are unpaid.

They do it for the combination of brutality, empowerment and flair that also draws a loyal audience.

“Roller derby has speed, grace, beauty and women trying to knock the crap out of each other,” said Joe Schwartz, a loyal derby junkie who brings a camera to capture the action on the track. “What’s not to like?”