Sports played with spheres are easier to master than rectangular sports, such as Rubik's cubing and throwing bricks into windows. Circle fun with today's Groupon: for $29, you get six beginner group tennis lessons at KTC Quail Tennis Club at Kettering Tennis Center in Kettering (a $59 value). Choose from class times on Tuesdays 9:30 a.m.–10:30 a.m., Fridays 6 p.m.–7 p.m., or Saturdays 10:30 a.m.–11:30 a.m. Classes begin the week of September 12th and are held at the Quail Run Racquet Club.

The USPTA pros at KTC Quail Tennis Club hail from as far away as Argentina, Brazil, and Russia, and many of them have competed at a collegiate, semiprofessional, or professional level. Gather inside an air-conditioned facility to wallop orbs across eight courts. Instructors lead classes weekly for six weeks, and supervise drills and playing time as players learn the rules, memorize the terminology, and practice serving with enough precision to knock a can of soda out of the hand of a rocketeer in midflight. After lessons, rinse off in separate men's and women's locker rooms. Classes are for both men and women, and no membership is required to participate.