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It is the first shoot 'em up arcade game to feature cooperative gameplay and the first game to exhibit "flocking" behavior. One or two players control tank-like vehicles while game-controlled "pirate" tanks rush onto the field and attempt to drag the canisters off the edge of the screen. One or two players attempt to protect fuel canisters from groups of invading pirate tanks that appear from the edges of the screen. There is no penalty to the player for destroying enemy tanks this way except for the brief period of time he is out of the game. A wave ends when all the pirate tanks have either been destroyed by the players or have dragged a fuel canister off the screen.
