The back-story is that this is a mining colony on Mars - the arena is an ancient Martian city that's been turned into a place for the miners to live - with a glass canopy enclosing the atmosphere. Since it's a low gravity world, miners can get around on a variety of human-powered flying machines - bicycle-powered helicopters, giant mutant eagles, jet-packs, etc. For fun, they play a game that's a bit like 3D football - flying around the arena - grabbing the ball using force-field "grabbers"...using huge ore buckets on cranes as goals...you get the idea.
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