is chess a game?
Archery is a sport, so is track and field and swimming. None of those require one team on offense and one on defense. Neither do they require exactly two teams, nor are the races (for track/cross country/swimming) always held at the same time. Strategy and skill tend to correspond with each other. You can just Google the answer to your question instead of asking it on a forum, but yes it is a game. I think that's everything.