This is a stand-alone expansion to the original game, with purple and green robot teams and updated rules for more than 2 players. 2 players can play this version by itself, but combined with additional copies of the expansion or the original version of the game, more players can play together. Play Players strategically select from their hand of robot cards as they attack and defend. Each time a player defeats their opponent's robot, they become the attacker on the next round. The defender has the advantage of choosing how to respond to the attacker's card, and may choose to sacrifice both robots to attempt to capture the robots in their opponent's hand. When one player runs out of cards, they are defeated and their opponent is the Robot Master of the World! -description from designer