Roller-skating battles date back to ancient Rome when elections were determined by which senator could out-skate Caligula’s horse. Soak up the sport of the ancients with today’s Groupon: for $13, you get two general-admission tickets to a roller-derby match with the Kansas City Roller Warriors on Saturday, August 13 (up to a $32 value). Kids 5 and younger are admitted for free.

The Kansas City Roller Warriors, created by derby girls Princess Anna Conda and Dirty Britches, in 2004, block, jam, and grand slam around the Municipal Auditorium. The Warrior’s All Star and Plan B squads will take on St. Louis in the final regular-season bout to determine, once and for all, whether computers are smarter than humans, or just humans dressed as computers. Tickets are general admission and first come, first served, so viewers should arrive early for shots at a souvenir elbow to the face.