A concept used in the book Ender's Game
, by Orson Scott Card
At the orbiting Battle School, much of the military training there revolved around use of the battleroom. Armies of 41 kids each (typically 4 toons of 10 kids with 1 commander) would engage in mock combat in a battleroom.
The battleroom's key feature was that it used nullo (had no gravity). Sometimes there would be obstacles within the room called stars, wihch were free-floating cubes distributed at random. The two opposing armies were fitted with flash suits and a type of gun which, when shot at a flash suit, would cause that part of the suit (or the entire suit, if a direct hit) to go rigid. Someone taking on a direct hit would be deemed frozen, and be out of play until the game reached completion.
The game was won by having four members of an army press their helmets to four corners of the enemy's gate while a fifth passed through. Typically, this wouldn't occur until everyone on the opposing team had been frozen or disabled.